FOUS30 KWBC 311924
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
224 PM EST Fri Jan 31 2025

Day 1
Valid 16Z Fri Jan 31 2025 - 12Z Sat Feb 01 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
WEST VIRGINIA AND NORTHERN ILLINOIS...

16Z Update...
Minor adjustments were made based on current observation trends and
the 12Z hi-res guidance; but overall, no large-scale changes were
made from the previous outlook.

Pereira

Previous Discussion...
...West Virginia...
Only minimal changes to the Slight risk area over portions of WV. The
latest NOHRSC analysis indicates upwards of 2-4" of snow water
equivalent over the terrain of eastern WV and the latest model
consensus continues to depict 1-3" of rainfall over this area.
With temperatures and dewpoints forecast to at least get into the
40s (50s in spots) the rain on snow should trigger a fairly
efficient melting of the snowpack. This is likely to result in
numerous instances of areal flooding and at least some river
flooding.

Rainfall rates are generally forecast to stay in the 0.25" to 0.5"
an hour range, which is probably not enough to generate flooding
of a more flashy variety. However there are indications in the 00z
HREF that embedded convective elements could locally push hourly
rainfall a bit over 0.5". Given the amount of runoff that will be
occurring from the combined snow melt and rain, any of these higher
rates could locally result in a flash flood threat as well.

...Northern Illinois and Indiana...
Only minor changes to the inherited Slight risk area within the
comma head rainfall axis over northern IL. Despite little to no
instability, strong frontogenesis within this axis is resulting in
moderate HREF probabilities of rainfall exceeding 0.5" in an hour.
Rainfall amounts upwards of 1.5" in 6 hrs should be enough to at
least trigger some minor flood impacts given the extra runoff
generated by the mostly frozen ground.

...West Coast...
An atmospheric river will bring heavy rainfall from western WA
southward into northern CA today into night. The IVT plume is
generally progressive and weakening through the period, so not
expecting major rainfall totals or impacts. Generally forecasting
1-3" of rainfall (locally higher in the favored terrain), which
should mainly drive an isolated minor flood threat.

The IVT axis does start to stall as it shifts into northern CA, and
so could be looking at totals locally in the 2-4" range across the
terrain here. Given the generally dry antecedent conditions still
think this initial batch of rain will mainly just set the stage
for a greater flood threat in the following days, so will keep the
risk at Marginal. However we may see at least some uptick in flood
related impacts over central to northern CA by tonight.

Chenard


Day 2
Valid 12Z Sat Feb 01 2025 - 12Z Sun Feb 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CALIFORNIA...

...1930 UTC Update...
Changes to the Day 2 ERO were mainly to expand the northern end of
the Slight Risk area a bit farther north across northern CA, to
include Redding and the Park Fire burn scar. This given the
guidance trends (with the 12Z runs) along with uptick in
0.25-0.50"/hr rainfall rates per the HREF. Meanwhile, the latest
CSU First-Guess ERO (UFVS verified version) supports the northern
extent of the Slight as well.

Hurley

...Discussion...
The atmospheric river is forecast to stall over central/northern=20
CA on Saturday. Most model solutions indicate an increase in IVT=20
moving into the CA coast near San Francisco just after 12z=20
Saturday, which should bring an uptick in rainfall rates onshore.=20
PWs will be quite impressive for the time of year, with values=20
forecast to exceed the 99th percentile. A lack of strong dynamics=20
and frontal convergence, combined with only moderate IVT values,=20
will cap the magnitude of rainfall rates. Nonetheless, expecting to
see enough of an uptick in rainfall Saturday with the stalling AR=20
to support an increase in flood impacts, warranting the Slight=20
risk.

While IVT values along coastal areas will be moderate, what this
AR will have going for it is an impressive inland extent of IVT magnitudes...with values exceeding the 99th percentile (and around climatological max values) within the Sierra. This supports the
inland extension of the Slight risk across the Sacramento Valley
and into the mountains. Snow levels will be high, so the Slight
risk extends pretty far into the terrain. We also made sure to
extend the Marginal risk over the crest and into the eastern slopes
of the Sierra, as given the IVT, we should see enough rain make it
over the crest to support at least a minor flood risk.

Two day rainfall totals are currently forecast upwards of 2-4"
along coastal areas, 1-3" within Sacramento valley locations, and
upwards of 4-7" within the Sierra Nevada (most of which will be
rain given high snow levels).

Chenard


Day 3
Valid 12Z Sun Feb 02 2025 - 12Z Mon Feb 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CALIFORNIA...


...1930 UTC Update...
Minimal changes were made to the Day 3 Slight and Marginal Risk
areas across northern CA and far western NV, based on the latest
(12Z) model guidance.=20

Hurley

...Discussion...
The slow moving atmospheric river will continue to bring a heavy=20
rainfall and flood threat to portions of northern CA Sunday into=20
Sunday night. The IVT core and max rainfall axis should shift a bit
north compared to day 2 (Saturday). PWs drop off compared to=20
earlier in the event, however the persistent IVT should support a=20
prolonged moderate to locally heavy rain. Snow levels are quite=20
high, and thus the Slight risk was expanded into the terrain, and=20
even a bit to the east of the crest given the inland IVT anomalies.
Rainfall rates within the higher terrain of the Sierra and just=20
downwind of the crest will more be driven by the persistent IVT=20
over the entire period, and thus flood impacts will be possible=20
through Sunday and into the overnight hours.

Along coastal and valley areas, rainfall rates should increase by
later Sunday night as convergence increases along a front moving
into the CA coast. Given what should be saturated conditions by
this time, this uptick in rainfall rates along coastal areas into
portions of the northern Sacramento Valley may result in an uptick
in flood impacts by later Sunday night.

Chenard

Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_FQCh-xOMUvh5_7UhpyFdMYFc-g7NJUrPOTt2b5-VBwP= 508CV_yFFF_T76xyEUGJF3qEnrqv5-G1fxjnj92XyU_psxU$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_FQCh-xOMUvh5_7UhpyFdMYFc-g7NJUrPOTt2b5-VBwP= 508CV_yFFF_T76xyEUGJF3qEnrqv5-G1fxjnj92XGzmohlg$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_FQCh-xOMUvh5_7UhpyFdMYFc-g7NJUrPOTt2b5-VBwP= 508CV_yFFF_T76xyEUGJF3qEnrqv5-G1fxjnj92X5Vt3DNk$=20

=3D =3D =3D
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FOUS30 KWBC 010023
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
723 PM EST Fri Jan 31 2025

Day 1
Valid 01Z Sat Feb 01 2025 - 12Z Sat Feb 01 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE APPALACHIANS AND PARTS OF THE WEST COAST...

West Virginia...
Main change from the previous outlook was to remove the Slight and
to remove the Marginal Risk area from all but far eastern West=20
Virginia where rainfall was lingering in/near the terrain. Drier=20
air should continue to filter eastward during the evening=20
hours...with a corresponding decrease in rainfall amounts. With=20
some higher reflectivity echoes still located upstream...did not=20
want to completely remove the Marginal risk area but certainly=20
reduced the areal coverage. Latest MRMS depicts maximum hourly=20
rainfall rates barely above 0.25 inches with 3-hour rainfall totals
generally remaining under 0.5 inches. This probably not enough to=20
generate flooding of a more flashy variety. However the right=20
combination of embedded convective elements over areas that have=20
already received rain and the amount of runoff that could occur=20
between the rainfall and snow melt...felt removing the risk areas=20
was a bit premature.

West Coast...=20
Persistent on-shore flow of deep moisture will continue to support
moderate to locally heavy rainfall from western Washington=20=20
southward into northern CA through tonight. The IVT plume is=20
generally progressive and weakening through the period, so not=20
expecting major rainfall totals or impacts. Generally forecasting=20
an additional 1 inch or less through 12Z Saturday with the higher=20
amounts in areas where the terrain is aligned perpendicular to the=20
wind direction. This would be the main driver for any isolated=20
minor flood threat overnight.

Bann


Day 2
Valid 12Z Sat Feb 01 2025 - 12Z Sun Feb 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CALIFORNIA...

...1930 UTC Update...
Changes to the Day 2 ERO were mainly to expand the northern end of
the Slight Risk area a bit farther north across northern CA, to
include Redding and the Park Fire burn scar. This given the
guidance trends (with the 12Z runs) along with uptick in
0.25-0.50"/hr rainfall rates per the HREF. Meanwhile, the latest
CSU First-Guess ERO (UFVS verified version) supports the northern
extent of the Slight as well.

Hurley

...Discussion...
The atmospheric river is forecast to stall over central/northern
CA on Saturday. Most model solutions indicate an increase in IVT
moving into the CA coast near San Francisco just after 12z
Saturday, which should bring an uptick in rainfall rates onshore.
PWs will be quite impressive for the time of year, with values
forecast to exceed the 99th percentile. A lack of strong dynamics
and frontal convergence, combined with only moderate IVT values,
will cap the magnitude of rainfall rates. Nonetheless, expecting to
see enough of an uptick in rainfall Saturday with the stalling AR
to support an increase in flood impacts, warranting the Slight
risk.

While IVT values along coastal areas will be moderate, what this
AR will have going for it is an impressive inland extent of IVT magnitudes...with values exceeding the 99th percentile (and around climatological max values) within the Sierra. This supports the
inland extension of the Slight risk across the Sacramento Valley
and into the mountains. Snow levels will be high, so the Slight
risk extends pretty far into the terrain. We also made sure to
extend the Marginal risk over the crest and into the eastern slopes
of the Sierra, as given the IVT, we should see enough rain make it
over the crest to support at least a minor flood risk.

Two day rainfall totals are currently forecast upwards of 2-4"
along coastal areas, 1-3" within Sacramento valley locations, and
upwards of 4-7" within the Sierra Nevada (most of which will be
rain given high snow levels).

Chenard


Day 3
Valid 12Z Sun Feb 02 2025 - 12Z Mon Feb 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CALIFORNIA...


...1930 UTC Update...
Minimal changes were made to the Day 3 Slight and Marginal Risk
areas across northern CA and far western NV, based on the latest
(12Z) model guidance.

Hurley

...Discussion...
The slow moving atmospheric river will continue to bring a heavy
rainfall and flood threat to portions of northern CA Sunday into
Sunday night. The IVT core and max rainfall axis should shift a bit
north compared to day 2 (Saturday). PWs drop off compared to
earlier in the event, however the persistent IVT should support a
prolonged moderate to locally heavy rain. Snow levels are quite
high, and thus the Slight risk was expanded into the terrain, and
even a bit to the east of the crest given the inland IVT anomalies.
Rainfall rates within the higher terrain of the Sierra and just
downwind of the crest will more be driven by the persistent IVT
over the entire period, and thus flood impacts will be possible
through Sunday and into the overnight hours.

Along coastal and valley areas, rainfall rates should increase by
later Sunday night as convergence increases along a front moving
into the CA coast. Given what should be saturated conditions by
this time, this uptick in rainfall rates along coastal areas into
portions of the northern Sacramento Valley may result in an uptick
in flood impacts by later Sunday night.

Chenard

Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4UhI-1koFWIkqR_lGCTHIVgj00J18s8ElR2dZe86tpwT= S-S8ZreIqiuy6_Y9vr88qfpFsx6sqVztfUVmOlX5rqrwaCQ$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4UhI-1koFWIkqR_lGCTHIVgj00J18s8ElR2dZe86tpwT= S-S8ZreIqiuy6_Y9vr88qfpFsx6sqVztfUVmOlX58ldu1k0$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4UhI-1koFWIkqR_lGCTHIVgj00J18s8ElR2dZe86tpwT= S-S8ZreIqiuy6_Y9vr88qfpFsx6sqVztfUVmOlX5anITpHM$=20

=3D =3D =3D
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FOUS30 KWBC 010757
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
257 AM EST Sat Feb 1 2025

Day 1
Valid 12Z Sat Feb 01 2025 - 12Z Sun Feb 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF=20
NORTHERN CALIFORNIA...

A nearly stationary positively tilted longwave trough will be=20
anchored across central British Columbia today. It will direct a=20
zonal but powerful 150+ kt jet streak into the Pacific Northwest.=20
The jet streak will in turn guide an atmospheric river (AR) moving=20
eastward after soaking Hawaii into northern California today. The=20
support of the zonal jet will allow the AR's moisture to extend well=20
inland from the coast, including into Nevada, Utah, Idaho, and=20
Wyoming. The areas getting the greatest rainfall will be the=20
northern Sierra Nevada mountains and secondarily the coastal ranges=20
around and north of the Bay Area. For just this Day 1 period, expect=20
4-6 inches of rain from west of Lake Tahoe north and west to about=20
Paradise, CA. 1-3 inches are expected for the northern Coastal=20
Ranges from the Bay Area through southern Trinity County.

IVT values for this atmospheric river event peak at around 850 kg/ms=20
around 18Z/10am PST in the Bay Area this morning according to both=20
GFS and EC ensemble output. While this alone is notable, it's far=20
from extreme. It will be the duration of this event that will make=20
it stand out from most ARs. While IVT values will drop closer to 500=20
kg/ms in the following days, they will remain elevated near that=20
level for 3 consecutive days after today. Using IVT as a proxy for=20
heavy rain, this would suggest the heaviest rain of the event will=20
be this afternoon and evening, but smaller disturbances responsible=20
for brief upticks in precipitation rates become increasingly=20
difficult to predict at extended time ranges, so it's very possible=20 additional heavy rainfall will occur in the subsequent days.

PWATs advecting into the coast with the AR will get as high as 1.25=20
inches today. NAEFS mean PWAT probabilities put this at the 98th=20
percentile as compared with a 30 year average. Additional flooding=20
concerns are also forecast around the 2024 Park Fire east of Red=20
Bluff and north of Chico. Here, hydrophobic soils and a lack of=20
vegetation will convert most, if not all of the rainfall to runoff,=20 resulting in locally worse flooding as compared with surrounding=20
areas.

Changes from the previous forecast were minimal, with expansions of=20
the Marginal Risk drawn in around Lassen N.P. The highest elevations=20
will see snow, but with such high snow levels (6,000-7,500 ft), the=20
large majority of the expected precipitation in northern California=20
will be in the form of rain. NASA Sport soil moisture imagery shows=20
much of Northern California's soils are below to well below normal,=20
so much of the rain, especially in the populated valleys should=20
start out as beneficial...whereas the flooding threat will be the=20
most impactful in the foothills of the Sierras.

Wegman


Day 2
Valid 12Z Sun Feb 02 2025 - 12Z Mon Feb 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF=20
NORTHERN CALIFORNIA...

The slow moving atmospheric river will continue to bring a heavy
rainfall and flood threat to portions of northern CA Sunday into
Sunday night. The IVT core and max rainfall axis should shift a bit
north compared to day 1 (Saturday). PW anomalies will gradually=20
drop, however the persistent IVT should support a prolonged=20
moderate to locally heavy rain. Snow levels are quite high, and=20
thus the Slight risk area goes into the northern Sierra, and even=20
a bit to the east of the crest given the strong inland IVT=20
anomalies.

The highest rainfall rates will likely be across portions of the
northern Sierra where more anomalous IVT will focus into the
terrain. 48hr rainfall amounts of 8-12" are forecast over portions
of the northern Sierra (generally from Placer up to Butte and=20
Plumas counties) through 12z Monday. This portion of the Sierra=20
has some of the highest 48hr ARI thresholds in the country, so=20
this region is clearly used to heavy rainfall amounts. With that=20
said, these forecast totals are still exceeding the 2 to 5yr=20
thresholds. Seems like it'll be a cold rain so not sure how much=20
SWE loss we'll get in the higher elevations where there is=20
snowpack (rain might mostly get absorbed into the snowpack). Given=20
these totals and periodic rates around 0.5" per hour, at least some
flood impacts appear likely, with higher end Slight risk=20
probabilities justified. The lack of convective rainfall rates,=20
combined with the fact this area can generally take quite a bit of=20
rain (as seen by the high ARI thresholds), suggests these higher=20
end Slight probabilities should suffice for now.

A prolonged steady rain along coastal to valley areas will result
in a widespread 1-3" of additional rainfall over the Slight risk=20
area, brining 48hr totals into the 3-6" range. A lack of strong=20
frontal convergence should keep rainfall rates lower here, but the
prolonged nature of the rain should still allow for an uptick in=20
flood impacts as conditions continue to saturate.

Chenard


Day 3
Valid 12Z Mon Feb 03 2025 - 12Z Tue Feb 04 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF=20
NORTHERN CALIFORNIA...

Not much change to the IVT axis is forecast into Monday, meaning=20
the prolonged moderate to heavy rainfall event will continue across
northern CA. Snow levels should begin to drop by this time=20
resulting in less impacts over the higher terrain of the Sierra,=20
but a continued uptick in flood impacts over coastal areas into the
foothills where conditions will continue to saturate. By Monday=20
afternoon model guidance indicates we should see a strengthening of
frontal convergence across northern CA, which should help drive an
uptick in rainfall rates along the coast.=20

Model spread begins to increase by day 3 with the 00z NAM and GFS=20
a bit further north with the heavier rainfall axis than the 00z=20
ECMWF, UKMET and GEM. Interestingly the 18z ECMWF AIFS is closer=20
to the GFS/NAM camp. Big picture wise the differences do not end=20
up having a major impact on QPF or the ERO (differences get bigger
on day 4), but if the further north GFS/NAM end up being right the
Slight risk area could end up shifting a bit north with future=20
updates. There is some potential for higher end Slight risk, or=20
maybe even MDT risk, probabilities along coastal areas given the=20
expected uptick in rainfall rates over what should be fairly=20
saturated ground conditions by this point. However a lack of=20
stronger dynamics and lack of instability interacting with the IVT=20
plume may prevent rates from getting high enough to cause more=20
widespread significant impacts. So will just maintain the Slight=20
risk for now, but either way anticipate at least some continued=20
flood impacts Monday and will continue to monitor trends.

Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_iPWbFb7QlmGUryZ8IkXSxd1l8BeN44jUiXHB-sIsPW1= qApMNQ4fN6KgJ6DMZaxLhKZcIM-3QUg0EKX3hLgAtIcpoyo$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_iPWbFb7QlmGUryZ8IkXSxd1l8BeN44jUiXHB-sIsPW1= qApMNQ4fN6KgJ6DMZaxLhKZcIM-3QUg0EKX3hLgAwOHz6x8$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_iPWbFb7QlmGUryZ8IkXSxd1l8BeN44jUiXHB-sIsPW1= qApMNQ4fN6KgJ6DMZaxLhKZcIM-3QUg0EKX3hLgAQ6ihzHo$=20

=3D =3D =3D
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FOUS30 KWBC 011611
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1111 AM EST Sat Feb 1 2025

Day 1
Valid 16Z Sat Feb 01 2025 - 12Z Sun Feb 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

...16Z update...

The large scale setup described below remains valid for the D1=20
period and the 12Z sounding from OAK showed a PWAT of 1.23 inches,=20
already above the climatological max via the SPC sounding=20
climatology. There have been some northward shifts in the IVT axis=20
and highest QPF with the 12Z HREF components compared to the 00Z=20
and 06Z members. IVT of roughly 800 kg/m/s will likely reach the=20
Coastal Ranges just north of San Francisco between 21Z-00Z this=20
afternoon before slowly translating north into northern California=20
for the remainder of the outlook period. Based on these trends, the
southern end of the outlook area was trimmed back a bit based on=20
the latest 12Z HREF guidance which only shows rates briefly getting
into the 0.25 to 0.50 in/hr range for the San Francisco metro late
this morning and afternoon with lower chances of higher rates to=20
the south. The focus for the highest rainfall totals and rates=20
looks to be into the Sierra Nevada Mountains from Butte and Plumas=20
counties down to roughly I-80 where 24 hour rainfall totals of=20
about 6 to 10 inches are shown by a majority of the 12Z HREF=20
guidance (except for the FV3, which tends to run low in these=20
atmospheric river setups). For the northern California Coastal=20
Ranges, 2 to 4 inches looks to be a reasonable estimate according=20
to the latest 12Z members of the HREF (slight increase from=20
previous guidance).

Otto

...previous discussion follows...


A nearly stationary positively tilted longwave trough will be
anchored across central British Columbia today. It will direct a
zonal but powerful 150+ kt jet streak into the Pacific Northwest.
The jet streak will in turn guide an atmospheric river (AR) moving
eastward after soaking Hawaii into northern California today. The
support of the zonal jet will allow the AR's moisture to extend well
inland from the coast, including into Nevada, Utah, Idaho, and
Wyoming. The areas getting the greatest rainfall will be the
northern Sierra Nevada mountains and secondarily the coastal ranges
around and north of the Bay Area. For just this Day 1 period, expect
4-6 inches of rain from west of Lake Tahoe north and west to about
Paradise, CA. 1-3 inches are expected for the northern Coastal
Ranges from the Bay Area through southern Trinity County.

IVT values for this atmospheric river event peak at around 850 kg/ms
around 18Z/10am PST in the Bay Area this morning according to both
GFS and EC ensemble output. While this alone is notable, it's far
from extreme. It will be the duration of this event that will make
it stand out from most ARs. While IVT values will drop closer to 500
kg/ms in the following days, they will remain elevated near that
level for 3 consecutive days after today. Using IVT as a proxy for
heavy rain, this would suggest the heaviest rain of the event will
be this afternoon and evening, but smaller disturbances responsible
for brief upticks in precipitation rates become increasingly
difficult to predict at extended time ranges, so it's very possible
additional heavy rainfall will occur in the subsequent days.

PWATs advecting into the coast with the AR will get as high as 1.25
inches today. NAEFS mean PWAT probabilities put this at the 98th
percentile as compared with a 30 year average. Additional flooding
concerns are also forecast around the 2024 Park Fire east of Red
Bluff and north of Chico. Here, hydrophobic soils and a lack of
vegetation will convert most, if not all of the rainfall to runoff,
resulting in locally worse flooding as compared with surrounding
areas.

Changes from the previous forecast were minimal, with expansions of
the Marginal Risk drawn in around Lassen N.P. The highest elevations
will see snow, but with such high snow levels (6,000-7,500 ft), the
large majority of the expected precipitation in northern California
will be in the form of rain. NASA Sport soil moisture imagery shows
much of Northern California's soils are below to well below normal,
so much of the rain, especially in the populated valleys should
start out as beneficial...whereas the flooding threat will be the
most impactful in the foothills of the Sierras.

Wegman


Day 2
Valid 12Z Sun Feb 02 2025 - 12Z Mon Feb 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

The slow moving atmospheric river will continue to bring a heavy
rainfall and flood threat to portions of northern CA Sunday into
Sunday night. The IVT core and max rainfall axis should shift a bit
north compared to day 1 (Saturday). PW anomalies will gradually
drop, however the persistent IVT should support a prolonged
moderate to locally heavy rain. Snow levels are quite high, and
thus the Slight risk area goes into the northern Sierra, and even
a bit to the east of the crest given the strong inland IVT
anomalies.

The highest rainfall rates will likely be across portions of the
northern Sierra where more anomalous IVT will focus into the
terrain. 48hr rainfall amounts of 8-12" are forecast over portions
of the northern Sierra (generally from Placer up to Butte and
Plumas counties) through 12z Monday. This portion of the Sierra
has some of the highest 48hr ARI thresholds in the country, so
this region is clearly used to heavy rainfall amounts. With that
said, these forecast totals are still exceeding the 2 to 5yr
thresholds. Seems like it'll be a cold rain so not sure how much
SWE loss we'll get in the higher elevations where there is
snowpack (rain might mostly get absorbed into the snowpack). Given
these totals and periodic rates around 0.5" per hour, at least some
flood impacts appear likely, with higher end Slight risk
probabilities justified. The lack of convective rainfall rates,
combined with the fact this area can generally take quite a bit of
rain (as seen by the high ARI thresholds), suggests these higher
end Slight probabilities should suffice for now.

A prolonged steady rain along coastal to valley areas will result
in a widespread 1-3" of additional rainfall over the Slight risk
area, brining 48hr totals into the 3-6" range. A lack of strong
frontal convergence should keep rainfall rates lower here, but the
prolonged nature of the rain should still allow for an uptick in
flood impacts as conditions continue to saturate.

Chenard


Day 3
Valid 12Z Mon Feb 03 2025 - 12Z Tue Feb 04 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

Not much change to the IVT axis is forecast into Monday, meaning
the prolonged moderate to heavy rainfall event will continue across
northern CA. Snow levels should begin to drop by this time
resulting in less impacts over the higher terrain of the Sierra,
but a continued uptick in flood impacts over coastal areas into the
foothills where conditions will continue to saturate. By Monday
afternoon model guidance indicates we should see a strengthening of
frontal convergence across northern CA, which should help drive an
uptick in rainfall rates along the coast.

Model spread begins to increase by day 3 with the 00z NAM and GFS
a bit further north with the heavier rainfall axis than the 00z
ECMWF, UKMET and GEM. Interestingly the 18z ECMWF AIFS is closer
to the GFS/NAM camp. Big picture wise the differences do not end
up having a major impact on QPF or the ERO (differences get bigger
on day 4), but if the further north GFS/NAM end up being right the
Slight risk area could end up shifting a bit north with future
updates. There is some potential for higher end Slight risk, or
maybe even MDT risk, probabilities along coastal areas given the
expected uptick in rainfall rates over what should be fairly
saturated ground conditions by this point. However a lack of
stronger dynamics and lack of instability interacting with the IVT
plume may prevent rates from getting high enough to cause more
widespread significant impacts. So will just maintain the Slight
risk for now, but either way anticipate at least some continued
flood impacts Monday and will continue to monitor trends.

Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!61k83MVs_byCt8yaNtUHs_sxY9kirEHVy_XoiK5lN3QI= Eyu6ysE2w2-TvxJhHh9o_CPTUJfn4-OeQ3cYeIQHl2NzgFU$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!61k83MVs_byCt8yaNtUHs_sxY9kirEHVy_XoiK5lN3QI= Eyu6ysE2w2-TvxJhHh9o_CPTUJfn4-OeQ3cYeIQHjrF-Psw$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!61k83MVs_byCt8yaNtUHs_sxY9kirEHVy_XoiK5lN3QI= Eyu6ysE2w2-TvxJhHh9o_CPTUJfn4-OeQ3cYeIQHnwJNZOc$=20

=3D =3D =3D
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FOUS30 KWBC 011930
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
230 PM EST Sat Feb 1 2025

Day 1
Valid 16Z Sat Feb 01 2025 - 12Z Sun Feb 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

...16Z update...

The large scale setup described below remains valid for the D1
period and the 12Z sounding from OAK showed a PWAT of 1.23 inches,
already above the climatological max via the SPC sounding
climatology. There have been some northward shifts in the IVT axis
and highest QPF with the 12Z HREF components compared to the 00Z
and 06Z members. IVT of roughly 800 kg/m/s will likely reach the
Coastal Ranges just north of San Francisco between 21Z-00Z this
afternoon before slowly translating north into northern California
for the remainder of the outlook period. Based on these trends, the
southern end of the outlook area was trimmed back a bit based on
the latest 12Z HREF guidance which only shows rates briefly getting
into the 0.25 to 0.50 in/hr range for the San Francisco metro late
this morning and afternoon with lower chances of higher rates to
the south. The focus for the highest rainfall totals and rates
looks to be into the Sierra Nevada Mountains from Butte and Plumas
counties down to roughly I-80 where 24 hour rainfall totals of
about 6 to 10 inches are shown by a majority of the 12Z HREF
guidance (except for the FV3, which tends to run low in these
atmospheric river setups). For the northern California Coastal
Ranges, 2 to 4 inches looks to be a reasonable estimate according
to the latest 12Z members of the HREF (slight increase from
previous guidance).

Otto

...previous discussion follows...


A nearly stationary positively tilted longwave trough will be
anchored across central British Columbia today. It will direct a
zonal but powerful 150+ kt jet streak into the Pacific Northwest.
The jet streak will in turn guide an atmospheric river (AR) moving
eastward after soaking Hawaii into northern California today. The
support of the zonal jet will allow the AR's moisture to extend well
inland from the coast, including into Nevada, Utah, Idaho, and
Wyoming. The areas getting the greatest rainfall will be the
northern Sierra Nevada mountains and secondarily the coastal ranges
around and north of the Bay Area. For just this Day 1 period, expect
4-6 inches of rain from west of Lake Tahoe north and west to about
Paradise, CA. 1-3 inches are expected for the northern Coastal
Ranges from the Bay Area through southern Trinity County.

IVT values for this atmospheric river event peak at around 850 kg/ms
around 18Z/10am PST in the Bay Area this morning according to both
GFS and EC ensemble output. While this alone is notable, it's far
from extreme. It will be the duration of this event that will make
it stand out from most ARs. While IVT values will drop closer to 500
kg/ms in the following days, they will remain elevated near that
level for 3 consecutive days after today. Using IVT as a proxy for
heavy rain, this would suggest the heaviest rain of the event will
be this afternoon and evening, but smaller disturbances responsible
for brief upticks in precipitation rates become increasingly
difficult to predict at extended time ranges, so it's very possible
additional heavy rainfall will occur in the subsequent days.

PWATs advecting into the coast with the AR will get as high as 1.25
inches today. NAEFS mean PWAT probabilities put this at the 98th
percentile as compared with a 30 year average. Additional flooding
concerns are also forecast around the 2024 Park Fire east of Red
Bluff and north of Chico. Here, hydrophobic soils and a lack of
vegetation will convert most, if not all of the rainfall to runoff,
resulting in locally worse flooding as compared with surrounding
areas.

Changes from the previous forecast were minimal, with expansions of
the Marginal Risk drawn in around Lassen N.P. The highest elevations
will see snow, but with such high snow levels (6,000-7,500 ft), the
large majority of the expected precipitation in northern California
will be in the form of rain. NASA Sport soil moisture imagery shows
much of Northern California's soils are below to well below normal,
so much of the rain, especially in the populated valleys should
start out as beneficial...whereas the flooding threat will be the
most impactful in the foothills of the Sierras.

Wegman


Day 2
Valid 12Z Sun Feb 02 2025 - 12Z Mon Feb 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

Daytime update...
Based on the 12Z guidance, made only a small adjustment north to=20
the previous outlook areas. Overall, models have remained
consistent showing a strong signal for heavy amounts -- especially
within the Slight Risk area. The heaviest totals are expected to
fall east of the northern Sacramento Valley into the Sierra Nevada
foothills. Neighborhood probabilities from the 12Z HREF indicate
that localized amounts of 8 inches or more -- falling mostly as
rain -- are likely within that area.

Previous Discussion...
The slow moving atmospheric river will continue to bring a heavy=20
rainfall and flood threat to portions of northern CA Sunday into=20
Sunday night. The IVT core and max rainfall axis should shift a bit
north compared to day 1 (Saturday). PW anomalies will gradually=20
drop, however the persistent IVT should support a prolonged=20
moderate to locally heavy rain. Snow levels are quite high, and=20
thus the Slight risk area goes into the northern Sierra, and even a
bit to the east of the crest given the strong inland IVT=20
anomalies.

The highest rainfall rates will likely be across portions of the
northern Sierra where more anomalous IVT will focus into the
terrain. 48hr rainfall amounts of 8-12" are forecast over portions
of the northern Sierra (generally from Placer up to Butte and
Plumas counties) through 12z Monday. This portion of the Sierra
has some of the highest 48hr ARI thresholds in the country, so
this region is clearly used to heavy rainfall amounts. With that
said, these forecast totals are still exceeding the 2 to 5yr
thresholds. Seems like it'll be a cold rain so not sure how much
SWE loss we'll get in the higher elevations where there is
snowpack (rain might mostly get absorbed into the snowpack). Given
these totals and periodic rates around 0.5" per hour, at least some
flood impacts appear likely, with higher end Slight risk
probabilities justified. The lack of convective rainfall rates,
combined with the fact this area can generally take quite a bit of
rain (as seen by the high ARI thresholds), suggests these higher
end Slight probabilities should suffice for now.

A prolonged steady rain along coastal to valley areas will result
in a widespread 1-3" of additional rainfall over the Slight risk
area, brining 48hr totals into the 3-6" range. A lack of strong
frontal convergence should keep rainfall rates lower here, but the
prolonged nature of the rain should still allow for an uptick in
flood impacts as conditions continue to saturate.

Pereira/Chenard


Day 3
Valid 12Z Mon Feb 03 2025 - 12Z Tue Feb 04 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

Daytime update...
No significant changes were made to the previous outlook areas.

Previous Discussion...
Not much change to the IVT axis is forecast=20
into Monday, meaning the prolonged moderate to heavy rainfall event
will continue across northern CA. Snow levels should begin to drop
by this time resulting in less impacts over the higher terrain of=20
the Sierra, but a continued uptick in flood impacts over coastal=20
areas into the foothills where conditions will continue to=20
saturate. By Monday afternoon model guidance indicates we should=20
see a strengthening of frontal convergence across northern CA,=20
which should help drive an uptick in rainfall rates along the=20
coast.

Model spread begins to increase by day 3 with the 00z NAM and GFS
a bit further north with the heavier rainfall axis than the 00z
ECMWF, UKMET and GEM. Interestingly the 18z ECMWF AIFS is closer
to the GFS/NAM camp. Big picture wise the differences do not end
up having a major impact on QPF or the ERO (differences get bigger
on day 4), but if the further north GFS/NAM end up being right the
Slight risk area could end up shifting a bit north with future
updates. There is some potential for higher end Slight risk, or
maybe even MDT risk, probabilities along coastal areas given the
expected uptick in rainfall rates over what should be fairly
saturated ground conditions by this point. However a lack of
stronger dynamics and lack of instability interacting with the IVT
plume may prevent rates from getting high enough to cause more
widespread significant impacts. So will just maintain the Slight
risk for now, but either way anticipate at least some continued
flood impacts Monday and will continue to monitor trends.

Pereira/Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-k_hX39ZtAFfO5OhMWXCUTcqOdvHR9S_kuJVe1Zi-e1n= xoxqzG_2zMMvxVxJRq9SO8jw0c8LoBGfPWeoeM4fjD0hSf0$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-k_hX39ZtAFfO5OhMWXCUTcqOdvHR9S_kuJVe1Zi-e1n= xoxqzG_2zMMvxVxJRq9SO8jw0c8LoBGfPWeoeM4f8BCx08Q$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-k_hX39ZtAFfO5OhMWXCUTcqOdvHR9S_kuJVe1Zi-e1n= xoxqzG_2zMMvxVxJRq9SO8jw0c8LoBGfPWeoeM4fkefwmFQ$=20

=3D =3D =3D
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FOUS30 KWBC 020052
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
752 PM EST Sat Feb 1 2025

Day 1
Valid 01Z Sun Feb 02 2025 - 12Z Sun Feb 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

...01Z update...

The large scale setup described below largely remains valid for the
remainder of the Day 1 period that ends at 02/12Z. The 00Z=20
sounding from OAK showed that the precipitable water value at OAK
had increased to 1.47 inches between 01/12Z and 02/00Z. The
northward shift in the axis of greatest moisture transport noted in
the 12Z numerical guidance persisted in the 18Z run of the NAM but
was reversed by the 18Z run of the GFS..although roughly 800=20
kg/m/s of moisture transport integrated over a deeper layer looks
to be on track for the Coastal Ranges near or just north of San=20
Francisco by early evening before slowly translating north into=20
northern California for the remainder of the outlook period.
Adjustments made to the outlook area still seem on track to cover
the shifts in the guidance. The expectation is that rainfall rates
should increase later tonight once some instability
develops...resulting in rainfall amounts through 12Z Sunday=20
morning of roughly 1 to 3 inches along the Coastal Ranges and 3 to
5 inches for the northern Sierra Nevada ranges (with locally higher
amounts favored terrain)...roughly from Amador to Butte counties=20
given the placement of a 35 to 50 kt west southwesterly flow axis at
850 mb.


Bann

...previous discussion follows...


A nearly stationary positively tilted longwave trough will be
anchored across central British Columbia today. It will direct a
zonal but powerful 150+ kt jet streak into the Pacific Northwest.
The jet streak will in turn guide an atmospheric river (AR) moving
eastward after soaking Hawaii into northern California today. The
support of the zonal jet will allow the AR's moisture to extend well
inland from the coast, including into Nevada, Utah, Idaho, and
Wyoming. The areas getting the greatest rainfall will be the
northern Sierra Nevada mountains and secondarily the coastal ranges
around and north of the Bay Area. For just this Day 1 period, expect
4-6 inches of rain from west of Lake Tahoe north and west to about
Paradise, CA. 1-3 inches are expected for the northern Coastal
Ranges from the Bay Area through southern Trinity County.

IVT values for this atmospheric river event peak at around 850 kg/ms
around 18Z/10am PST in the Bay Area this morning according to both
GFS and EC ensemble output. While this alone is notable, it's far
from extreme. It will be the duration of this event that will make
it stand out from most ARs. While IVT values will drop closer to 500
kg/ms in the following days, they will remain elevated near that
level for 3 consecutive days after today. Using IVT as a proxy for
heavy rain, this would suggest the heaviest rain of the event will
be this afternoon and evening, but smaller disturbances responsible
for brief upticks in precipitation rates become increasingly
difficult to predict at extended time ranges, so it's very possible
additional heavy rainfall will occur in the subsequent days.

PWATs advecting into the coast with the AR will get as high as 1.25
inches today. NAEFS mean PWAT probabilities put this at the 98th
percentile as compared with a 30 year average. Additional flooding
concerns are also forecast around the 2024 Park Fire east of Red
Bluff and north of Chico. Here, hydrophobic soils and a lack of
vegetation will convert most, if not all of the rainfall to runoff,
resulting in locally worse flooding as compared with surrounding
areas.

Changes from the previous forecast were minimal, with expansions of
the Marginal Risk drawn in around Lassen N.P. The highest elevations
will see snow, but with such high snow levels (6,000-7,500 ft), the
large majority of the expected precipitation in northern California
will be in the form of rain. NASA Sport soil moisture imagery shows
much of Northern California's soils are below to well below normal,
so much of the rain, especially in the populated valleys should
start out as beneficial...whereas the flooding threat will be the
most impactful in the foothills of the Sierras.

Wegman


Day 2
Valid 12Z Sun Feb 02 2025 - 12Z Mon Feb 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

Daytime update...
Based on the 12Z guidance, made only a small adjustment north to
the previous outlook areas. Overall, models have remained
consistent showing a strong signal for heavy amounts -- especially
within the Slight Risk area. The heaviest totals are expected to
fall east of the northern Sacramento Valley into the Sierra Nevada
foothills. Neighborhood probabilities from the 12Z HREF indicate
that localized amounts of 8 inches or more -- falling mostly as
rain -- are likely within that area.

Previous Discussion...
The slow moving atmospheric river will continue to bring a heavy
rainfall and flood threat to portions of northern CA Sunday into
Sunday night. The IVT core and max rainfall axis should shift a bit
north compared to day 1 (Saturday). PW anomalies will gradually
drop, however the persistent IVT should support a prolonged
moderate to locally heavy rain. Snow levels are quite high, and
thus the Slight risk area goes into the northern Sierra, and even a
bit to the east of the crest given the strong inland IVT
anomalies.

The highest rainfall rates will likely be across portions of the
northern Sierra where more anomalous IVT will focus into the
terrain. 48hr rainfall amounts of 8-12" are forecast over portions
of the northern Sierra (generally from Placer up to Butte and
Plumas counties) through 12z Monday. This portion of the Sierra
has some of the highest 48hr ARI thresholds in the country, so
this region is clearly used to heavy rainfall amounts. With that
said, these forecast totals are still exceeding the 2 to 5yr
thresholds. Seems like it'll be a cold rain so not sure how much
SWE loss we'll get in the higher elevations where there is
snowpack (rain might mostly get absorbed into the snowpack). Given
these totals and periodic rates around 0.5" per hour, at least some
flood impacts appear likely, with higher end Slight risk
probabilities justified. The lack of convective rainfall rates,
combined with the fact this area can generally take quite a bit of
rain (as seen by the high ARI thresholds), suggests these higher
end Slight probabilities should suffice for now.

A prolonged steady rain along coastal to valley areas will result
in a widespread 1-3" of additional rainfall over the Slight risk
area, brining 48hr totals into the 3-6" range. A lack of strong
frontal convergence should keep rainfall rates lower here, but the
prolonged nature of the rain should still allow for an uptick in
flood impacts as conditions continue to saturate.

Pereira/Chenard


Day 3
Valid 12Z Mon Feb 03 2025 - 12Z Tue Feb 04 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

Daytime update...
No significant changes were made to the previous outlook areas.

Previous Discussion...
Not much change to the IVT axis is forecast
into Monday, meaning the prolonged moderate to heavy rainfall event
will continue across northern CA. Snow levels should begin to drop
by this time resulting in less impacts over the higher terrain of
the Sierra, but a continued uptick in flood impacts over coastal
areas into the foothills where conditions will continue to
saturate. By Monday afternoon model guidance indicates we should
see a strengthening of frontal convergence across northern CA,
which should help drive an uptick in rainfall rates along the
coast.

Model spread begins to increase by day 3 with the 00z NAM and GFS
a bit further north with the heavier rainfall axis than the 00z
ECMWF, UKMET and GEM. Interestingly the 18z ECMWF AIFS is closer
to the GFS/NAM camp. Big picture wise the differences do not end
up having a major impact on QPF or the ERO (differences get bigger
on day 4), but if the further north GFS/NAM end up being right the
Slight risk area could end up shifting a bit north with future
updates. There is some potential for higher end Slight risk, or
maybe even MDT risk, probabilities along coastal areas given the
expected uptick in rainfall rates over what should be fairly
saturated ground conditions by this point. However a lack of
stronger dynamics and lack of instability interacting with the IVT
plume may prevent rates from getting high enough to cause more
widespread significant impacts. So will just maintain the Slight
risk for now, but either way anticipate at least some continued
flood impacts Monday and will continue to monitor trends.

Pereira/Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5Yag52idsEQv2VgxpmBESMcj9mCuDCvrVcImrTAEnqLj= Jva6fdK9FjPyW0tKwu7YYef97QpeaPe5dC2EahgHEsEK4a4$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5Yag52idsEQv2VgxpmBESMcj9mCuDCvrVcImrTAEnqLj= Jva6fdK9FjPyW0tKwu7YYef97QpeaPe5dC2EahgHl6moq0w$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5Yag52idsEQv2VgxpmBESMcj9mCuDCvrVcImrTAEnqLj= Jva6fdK9FjPyW0tKwu7YYef97QpeaPe5dC2EahgHGM17k5I$=20

=3D =3D =3D
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FOUS30 KWBC 020803
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
303 AM EST Sun Feb 2 2025

Day 1
Valid 12Z Sun Feb 02 2025 - 12Z Mon Feb 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF NORTHERN=20 CALIFORNIA...

A prolonged atmospheric river (AR) event is underway across almost=20
all of northern California this morning. A large area of high=20
pressure off southern California is teaming up with a pair of=20
lows...one well north of Hawaii and the second near the northern tip=20
of Vancouver Island, BC. These features will interact to form a long=20 corridor where abundant tropical moisture can continue riding=20
northeastward from the tropics and into northern California.=20
Meanwhile, the lows are limiting the northward extent of the=20
moisture, especially the one off Canada, which is supplying colder=20
air into Oregon and Washington State.=20

In the upper levels, a stationary upper level low will guide upper=20
level disturbances around its southern periphery and into northern=20 California throughout this period, perhaps even retrograding a bit=20
west by tonight which will only further lengthen the fetch over the=20
Pacific. The strong high in place near southern California will form=20
a tight gradient between the two features, resulting in a=20
hyperactive zonal jet which will support continuous forcing for lift=20 supporting the rainfall within the AR.

Nasa Sport Soil Moisture imagery shows much of the soils of northern=20 California have become nearly saturated as a result of the 1-4=20
inches of rain that fell yesterday through the time of this writing.=20
Thus, expect much of the rainfall going forward associated with this=20
AR to largely convert to runoff.=20

A pair of upper level disturbances are moving along the atmospheric=20
river. The first will clear California and move into the interior=20
this morning. Heavy rain ongoing now over far northern California=20
will gradually drift south through the day in response to this first=20 disturbnace. This will give coastal regions a brief break in the=20
rainfall behind the disturbance from the start of this period=20
through late morning/midday. Then the second disturbance will renew=20
the heavy rainfall beginning midday/early afternoon and continue=20
right through tonight. The rainfall plume with this second round of=20
rain will be very slow to move, only crawling northward with time.=20
Most areas of far northern California will see several hours of=20
continuous, steady rain. Rates don't look to be quite as high with=20
this second disturbance, likely averaging between 1/4 and 1/2 inch=20
per hour. Thus, the primary hazards with it will be associated with=20
the long-duration of the rain.

Potential impacts from this AR today and tonight include possible=20
mudslides and rock slides in the foothills and mountains below snow=20
level (~6,500 ft), as well as the potential for localized flooding=20
in flood sensitive and low-lying areas with poor drainage.=20

Wegman


Day 2
Valid 12Z Mon Feb 03 2025 - 12Z Tue Feb 04 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

Not much change to the IVT axis is forecast into Monday, meaning=20
the prolonged moderate to heavy rainfall event will continue across
northern CA. Snow levels should begin to drop by this time=20
resulting in less impacts over the higher terrain of the Sierra,=20
but a continued uptick in flood impacts over coastal areas into the
foothills where conditions will continue to saturate. Model=20
guidance continues to show a strengthening of the frontal=20
convergence by this time over northern CA to go along with an=20
uptick in IVT values moving into the coast. This should result in=20
an increase in rainfall rates by late morning into the early=20
afternoon, with this axis of higher rates shifting south through=20
the afternoon and evening.

There is some potential for higher end Slight risk, or maybe even=20
MDT risk, probabilities along coastal areas given the expected=20
uptick in rainfall rates over what should be fairly saturated=20
ground conditions by this point. However a lack of stronger=20
dynamics, and lack of instability interacting with the IVT plume,
should put a cap on upward vertical motion and rainfall rates.
Thus while some flooding impacts appear likely, more widespread
significant impacts may be harder to come by, and thus not=20
planning on any upgrade at this time.

Chenard

Day 3
Valid 12Z Tue Feb 04 2025 - 12Z Wed Feb 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL AND NORTHERN CALIFORNIA...

The atmospheric river will continue dropping southward on Tuesday,
bringing another day of moderate to heavy rainfall and some
flooding risk. Still some uncertainty with the latitude of the AR=20
by this time, although models do appear to be converging on a=20
solution covered by the Slight risk area. Some trimming on the=20
northern end of the Slight risk may eventually be warranted, but=20
with some lingering uncertainty and the saturated conditions over=20
that area, we were a bit conservative with the northern extent of=20
the risk area.

Model solutions indicate the approach of a mid level shortwave
and a stronger upper jet after 18z Tuesday. These features will=20
help drive an increase in IVT, and may also help briefly stall the
southward progression of the front. Thus it appears likely that we
will see an uptick in rainfall rates after 18z Tuesday from=20
approximately San Francisco south into Monterey county. Still some=20 uncertainty on the exact location of this enhanced rainfall rate=20
activity, as well as exactly how intense the rain will be...but=20
current model solutions support upwards of 1.5" in a 3 hour=20
period, and 2-4" in total. This rainfall will likely drive an=20
increase in the flood threat over these areas. Luckily most of the=20
heavier rainfall on the preceding days will have been north of this
corridor, so not expecting conditions to be too saturated leading=20
into the uptick in rain. This fact, combined with the overall=20 progressiveness of the system, keeps the flood risk at a Slight=20
level. Although will need to continue to monitor, as if rainfall=20
rates trend higher can not rule out a localized corridor of MDT=20
risk level impacts.

The Marginal risk extends further down the coast into Santa
Barbara, Ventura and Los Angeles counties. The front should be
quick moving by the time it makes it this far south, but a=20
quick shot of heavy rainfall is possible. The 00z GFS and NAM do=20
not bring the better moisture transport this far south, however the
00z ECMWF, UKMET and GEM do. Even these latter models only get=20
rainfall totals into the 1-2" range given the fast frontal motion.
So generally not expecting widespread or significant impacts at=20
this time, although rainfall rates could be briefly high enough to=20
result in some localized minor flood concerns. We will keep a close
eye on the sensitive burn scars over Los Angeles county, but at=20
this time even the more aggressive ECMWF would suggest rainfall=20
rates will be on the decline by the time they get that far south.=20
Will need to continue to monitor, but think a Marginal risk will=20
suffice for now.

Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8AQ7NNcA7NmaF72avmy4yHjy75InlevaHGj3nDmfa3os= ryEq2TvCsShbBFNnMJ4D7nahxjvlD7qJ3KzhwReEdvjdv0A$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8AQ7NNcA7NmaF72avmy4yHjy75InlevaHGj3nDmfa3os= ryEq2TvCsShbBFNnMJ4D7nahxjvlD7qJ3KzhwReEdh4XNJo$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8AQ7NNcA7NmaF72avmy4yHjy75InlevaHGj3nDmfa3os= ryEq2TvCsShbBFNnMJ4D7nahxjvlD7qJ3KzhwReELzxUKBI$=20

=3D =3D =3D
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FOUS30 KWBC 021600
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1100 AM EST Sun Feb 2 2025

Day 1
Valid 16Z Sun Feb 02 2025 - 12Z Mon Feb 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF NORTHERN CALIFORNIA...

...16Z update...

The only change with this update was to trim back the southern
portion of the Slight Risk over the northern California Coastal
Ranges. As the ongoing surge of heavier rainfall wanes into the
afternoon, additional rainfall rates through the rest of the day
into tonight look to be less than 0.5 in/hr and less impactful.

As mentioned in the previous discussion, a surge of
heavy rain has been ongoing this morning with several reports of=20
hourly rainfall in excess of 0.5 inches across the northern Sierra=20
Nevada. Peak IVT values are forecast by the 06Z GFS to lower from=20
the earlier morning values of 700-800 kg/m/s into the 400-600=20
kg/m/s range for the remainder of the period (through 12Z Monday).=20
This steady influx of moisture will continue to carry the potential
for hourly rainfall in excess of 0.5 inches but the coverage of=20
these higher rates should shrink. Nonetheless, in advance of the=20
next mid- level shortwave impulse from the west, rainfall rates=20
will increase slightly tonight with steady rain continuing through=20
12Z Monday. Peak additional rainfall totals through 12Z Monday for=20
the northern California Coastal Ranges are expected to be 3-5=20
inches and 5-10 inches for the northern Sierra Nevada.=20

Otto

...previous discussion follows...


A prolonged atmospheric river (AR) event is underway across almost
all of northern California this morning. A large area of high
pressure off southern California is teaming up with a pair of
lows...one well north of Hawaii and the second near the northern tip
of Vancouver Island, BC. These features will interact to form a long
corridor where abundant tropical moisture can continue riding
northeastward from the tropics and into northern California.
Meanwhile, the lows are limiting the northward extent of the
moisture, especially the one off Canada, which is supplying colder
air into Oregon and Washington State.

In the upper levels, a stationary upper level low will guide upper
level disturbances around its southern periphery and into northern
California throughout this period, perhaps even retrograding a bit
west by tonight which will only further lengthen the fetch over the
Pacific. The strong high in place near southern California will form
a tight gradient between the two features, resulting in a
hyperactive zonal jet which will support continuous forcing for lift
supporting the rainfall within the AR.

Nasa Sport Soil Moisture imagery shows much of the soils of northern
California have become nearly saturated as a result of the 1-4
inches of rain that fell yesterday through the time of this writing.
Thus, expect much of the rainfall going forward associated with this
AR to largely convert to runoff.

A pair of upper level disturbances are moving along the atmospheric
river. The first will clear California and move into the interior
this morning. Heavy rain ongoing now over far northern California
will gradually drift south through the day in response to this first disturbance. This will give coastal regions a brief break in the
rainfall behind the disturbance from the start of this period
through late morning/midday. Then the second disturbance will renew
the heavy rainfall beginning midday/early afternoon and continue
right through tonight. The rainfall plume with this second round of
rain will be very slow to move, only crawling northward with time.
Most areas of far northern California will see several hours of
continuous, steady rain. Rates don't look to be quite as high with
this second disturbance, likely averaging between 1/4 and 1/2 inch
per hour. Thus, the primary hazards with it will be associated with
the long-duration of the rain.

Potential impacts from this AR today and tonight include possible
mudslides and rock slides in the foothills and mountains below snow
level (~6,500 ft), as well as the potential for localized flooding
in flood sensitive and low-lying areas with poor drainage.

Wegman


Day 2
Valid 12Z Mon Feb 03 2025 - 12Z Tue Feb 04 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

Not much change to the IVT axis is forecast into Monday, meaning
the prolonged moderate to heavy rainfall event will continue across
northern CA. Snow levels should begin to drop by this time
resulting in less impacts over the higher terrain of the Sierra,
but a continued uptick in flood impacts over coastal areas into the
foothills where conditions will continue to saturate. Model
guidance continues to show a strengthening of the frontal
convergence by this time over northern CA to go along with an
uptick in IVT values moving into the coast. This should result in
an increase in rainfall rates by late morning into the early
afternoon, with this axis of higher rates shifting south through
the afternoon and evening.

There is some potential for higher end Slight risk, or maybe even
MDT risk, probabilities along coastal areas given the expected
uptick in rainfall rates over what should be fairly saturated
ground conditions by this point. However a lack of stronger
dynamics, and lack of instability interacting with the IVT plume,
should put a cap on upward vertical motion and rainfall rates.
Thus while some flooding impacts appear likely, more widespread
significant impacts may be harder to come by, and thus not
planning on any upgrade at this time.

Chenard

Day 3
Valid 12Z Tue Feb 04 2025 - 12Z Wed Feb 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL AND NORTHERN CALIFORNIA...

The atmospheric river will continue dropping southward on Tuesday,
bringing another day of moderate to heavy rainfall and some
flooding risk. Still some uncertainty with the latitude of the AR
by this time, although models do appear to be converging on a
solution covered by the Slight risk area. Some trimming on the
northern end of the Slight risk may eventually be warranted, but
with some lingering uncertainty and the saturated conditions over
that area, we were a bit conservative with the northern extent of
the risk area.

Model solutions indicate the approach of a mid level shortwave
and a stronger upper jet after 18z Tuesday. These features will
help drive an increase in IVT, and may also help briefly stall the
southward progression of the front. Thus it appears likely that we
will see an uptick in rainfall rates after 18z Tuesday from
approximately San Francisco south into Monterey county. Still some
uncertainty on the exact location of this enhanced rainfall rate
activity, as well as exactly how intense the rain will be...but
current model solutions support upwards of 1.5" in a 3 hour
period, and 2-4" in total. This rainfall will likely drive an
increase in the flood threat over these areas. Luckily most of the
heavier rainfall on the preceding days will have been north of this
corridor, so not expecting conditions to be too saturated leading
into the uptick in rain. This fact, combined with the overall
progressiveness of the system, keeps the flood risk at a Slight
level. Although will need to continue to monitor, as if rainfall
rates trend higher can not rule out a localized corridor of MDT
risk level impacts.

The Marginal risk extends further down the coast into Santa
Barbara, Ventura and Los Angeles counties. The front should be
quick moving by the time it makes it this far south, but a
quick shot of heavy rainfall is possible. The 00z GFS and NAM do
not bring the better moisture transport this far south, however the
00z ECMWF, UKMET and GEM do. Even these latter models only get
rainfall totals into the 1-2" range given the fast frontal motion.
So generally not expecting widespread or significant impacts at
this time, although rainfall rates could be briefly high enough to
result in some localized minor flood concerns. We will keep a close
eye on the sensitive burn scars over Los Angeles county, but at
this time even the more aggressive ECMWF would suggest rainfall
rates will be on the decline by the time they get that far south.
Will need to continue to monitor, but think a Marginal risk will
suffice for now.

Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5kDBnQnDosIAjM5IJuFXfw-qedveltS6DCHTIj3pET3u= 57yy8YZV3Ad5sjijx5KE31zhdfSAhIfSN9tdmxQq0L_t7iQ$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5kDBnQnDosIAjM5IJuFXfw-qedveltS6DCHTIj3pET3u= 57yy8YZV3Ad5sjijx5KE31zhdfSAhIfSN9tdmxQqYVrpd_E$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5kDBnQnDosIAjM5IJuFXfw-qedveltS6DCHTIj3pET3u= 57yy8YZV3Ad5sjijx5KE31zhdfSAhIfSN9tdmxQqQVIpzjQ$=20

=3D =3D =3D
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FOUS30 KWBC 021936
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
236 PM EST Sun Feb 2 2025

Day 1
Valid 16Z Sun Feb 02 2025 - 12Z Mon Feb 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF NORTHERN CALIFORNIA...

...16Z update...

The only change with this update was to trim back the southern
portion of the Slight Risk over the northern California Coastal
Ranges. As the ongoing surge of heavier rainfall wanes into the
afternoon, additional rainfall rates through the rest of the day
into tonight look to be less than 0.5 in/hr and less impactful.

As mentioned in the previous discussion, a surge of
heavy rain has been ongoing this morning with several reports of
hourly rainfall in excess of 0.5 inches across the northern Sierra
Nevada. Peak IVT values are forecast by the 06Z GFS to lower from
the earlier morning values of 700-800 kg/m/s into the 400-600
kg/m/s range for the remainder of the period (through 12Z Monday).
This steady influx of moisture will continue to carry the potential
for hourly rainfall in excess of 0.5 inches but the coverage of
these higher rates should shrink. Nonetheless, in advance of the
next mid- level shortwave impulse from the west, rainfall rates
will increase slightly tonight with steady rain continuing through
12Z Monday. Peak additional rainfall totals through 12Z Monday for
the northern California Coastal Ranges are expected to be 3-5
inches and 5-10 inches for the northern Sierra Nevada.

Otto

...previous discussion follows...


A prolonged atmospheric river (AR) event is underway across almost
all of northern California this morning. A large area of high
pressure off southern California is teaming up with a pair of
lows...one well north of Hawaii and the second near the northern tip
of Vancouver Island, BC. These features will interact to form a long
corridor where abundant tropical moisture can continue riding
northeastward from the tropics and into northern California.
Meanwhile, the lows are limiting the northward extent of the
moisture, especially the one off Canada, which is supplying colder
air into Oregon and Washington State.

In the upper levels, a stationary upper level low will guide upper
level disturbances around its southern periphery and into northern
California throughout this period, perhaps even retrograding a bit
west by tonight which will only further lengthen the fetch over the
Pacific. The strong high in place near southern California will form
a tight gradient between the two features, resulting in a
hyperactive zonal jet which will support continuous forcing for lift
supporting the rainfall within the AR.

NASA Sport Soil Moisture imagery shows much of the soils of=20
northern California have become nearly saturated as a result of the
1-4 inches of rain that fell yesterday through the time of this=20
writing. Thus, expect much of the rainfall going forward associated
with this AR to largely convert to runoff.

A pair of upper level disturbances are moving along the atmospheric
river. The first will clear California and move into the interior
this morning. Heavy rain ongoing now over far northern California
will gradually drift south through the day in response to this first disturbance. This will give coastal regions a brief break in the
rainfall behind the disturbance from the start of this period
through late morning/midday. Then the second disturbance will renew
the heavy rainfall beginning midday/early afternoon and continue
right through tonight. The rainfall plume with this second round of
rain will be very slow to move, only crawling northward with time.
Most areas of far northern California will see several hours of
continuous, steady rain. Rates don't look to be quite as high with
this second disturbance, likely averaging between 1/4 and 1/2 inch
per hour. Thus, the primary hazards with it will be associated with
the long-duration of the rain.

Potential impacts from this AR today and tonight include possible
mudslides and rock slides in the foothills and mountains below snow
level (~6,500 ft), as well as the potential for localized flooding
in flood sensitive and low-lying areas with poor drainage.

Wegman


Day 2
Valid 12Z Mon Feb 03 2025 - 12Z Tue Feb 04 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

19Z Update...
No significant changes were made to the previous outlook areas.

Previous Discussion...=20
Not much change to the IVT axis is forecast
into Monday, meaning the prolonged moderate to heavy rainfall=20
event will continue across northern CA. Snow levels should begin to
drop by this time resulting in less impacts over the higher=20
terrain of the Sierra, but a continued uptick in flood impacts over
coastal areas into the foothills where conditions will continue to
saturate. Model guidance continues to show a strengthening of the=20
frontal convergence by this time over northern CA to go along with=20
an uptick in IVT values moving into the coast. This should result=20
in an increase in rainfall rates by late morning into the early=20
afternoon, with this axis of higher rates shifting south through=20
the afternoon and evening.

There is some potential for higher end Slight risk, or maybe even
MDT risk, probabilities along coastal areas given the expected
uptick in rainfall rates over what should be fairly saturated
ground conditions by this point. However a lack of stronger
dynamics, and lack of instability interacting with the IVT plume,
should put a cap on upward vertical motion and rainfall rates.
Thus while some flooding impacts appear likely, more widespread
significant impacts may be harder to come by, and thus not
planning on any upgrade at this time.

Pereira/Chenard

Day 3
Valid 12Z Tue Feb 04 2025 - 12Z Wed Feb 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL AND NORTHERN CALIFORNIA...

19Z Update...
No significant changes were made to the previous outlook areas.

Previous Discussion...
The atmospheric river will continue dropping southward on Tuesday,
bringing another day of moderate to heavy rainfall and some
flooding risk. Still some uncertainty with the latitude of the AR
by this time, although models do appear to be converging on a
solution covered by the Slight risk area. Some trimming on the
northern end of the Slight risk may eventually be warranted, but
with some lingering uncertainty and the saturated conditions over
that area, we were a bit conservative with the northern extent of
the risk area.

Model solutions indicate the approach of a mid level shortwave
and a stronger upper jet after 18z Tuesday. These features will
help drive an increase in IVT, and may also help briefly stall the
southward progression of the front. Thus it appears likely that we
will see an uptick in rainfall rates after 18z Tuesday from
approximately San Francisco south into Monterey county. Still some
uncertainty on the exact location of this enhanced rainfall rate
activity, as well as exactly how intense the rain will be...but
current model solutions support upwards of 1.5" in a 3 hour
period, and 2-4" in total. This rainfall will likely drive an
increase in the flood threat over these areas. Luckily most of the
heavier rainfall on the preceding days will have been north of this
corridor, so not expecting conditions to be too saturated leading
into the uptick in rain. This fact, combined with the overall
progressiveness of the system, keeps the flood risk at a Slight
level. Although will need to continue to monitor, as if rainfall
rates trend higher can not rule out a localized corridor of MDT
risk level impacts.

The Marginal risk extends further down the coast into Santa
Barbara, Ventura and Los Angeles counties. The front should be
quick moving by the time it makes it this far south, but a
quick shot of heavy rainfall is possible. The 00z GFS and NAM do
not bring the better moisture transport this far south, however the
00z ECMWF, UKMET and GEM do. Even these latter models only get
rainfall totals into the 1-2" range given the fast frontal motion.
So generally not expecting widespread or significant impacts at
this time, although rainfall rates could be briefly high enough to
result in some localized minor flood concerns. We will keep a close
eye on the sensitive burn scars over Los Angeles county, but at
this time even the more aggressive ECMWF would suggest rainfall
rates will be on the decline by the time they get that far south.
Will need to continue to monitor, but think a Marginal risk will
suffice for now.

Pereira/Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6Pf3C6wLAtAbMu7hSpJJdArwzWn4S8AVG8HYT-DFBn16= bsSTAB8itgad5X7olt5hbuBeEBA73-wUV_Z-iy39xZ5SPMQ$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6Pf3C6wLAtAbMu7hSpJJdArwzWn4S8AVG8HYT-DFBn16= bsSTAB8itgad5X7olt5hbuBeEBA73-wUV_Z-iy39__3KhZU$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6Pf3C6wLAtAbMu7hSpJJdArwzWn4S8AVG8HYT-DFBn16= bsSTAB8itgad5X7olt5hbuBeEBA73-wUV_Z-iy391y-Zbpk$=20

=3D =3D =3D
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FOUS30 KWBC 030047
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
747 PM EST Sun Feb 2 2025

Day 1
Valid 01Z Mon Feb 03 2025 - 12Z Mon Feb 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF NORTHERN CALIFORNIA...

The only change with this update was to nudge the northern portion
of the Marginal risk area northward a bit in deference to radar=20
trends as of late aternoon...but few (if any changes) needed=20
elsewhere. Given instability forecasts from the high resolution=20 guidance...earlier thinking that rates should gradually wane with=20
rates settling under 0.5 in/hr and less impactful still seems to be
on track.

A surge of heavy rain has persisted across portions of northern
California from this morning into the afternoon with several=20
reports of hourly rainfall in excess of 0.5 inches across the=20
northern Sierra Nevada. Peak IVT values are forecast by the 12Z and
18Z GFS to lower from the earlier morning values of 700-800 kg/m/s
into the 400-600 kg/m/s range for the remainder of the period=20
(through 12Z Monday). This steady influx of moisture will continue=20
to carry the potential for hourly rainfall in excess of 0.5 inches=20
but the coverage of these higher rates should shrink. Nonetheless,=20
in advance of the next mid- level shortwave impulse from the west,=20
rainfall rates will increase slightly tonight with steady rain=20
continuing through 12Z Monday.=20

Bann


Day 2
Valid 12Z Mon Feb 03 2025 - 12Z Tue Feb 04 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

19Z Update...
No significant changes were made to the previous outlook areas.

Previous Discussion...
Not much change to the IVT axis is forecast
into Monday, meaning the prolonged moderate to heavy rainfall
event will continue across northern CA. Snow levels should begin to
drop by this time resulting in less impacts over the higher
terrain of the Sierra, but a continued uptick in flood impacts over
coastal areas into the foothills where conditions will continue to
saturate. Model guidance continues to show a strengthening of the
frontal convergence by this time over northern CA to go along with
an uptick in IVT values moving into the coast. This should result
in an increase in rainfall rates by late morning into the early
afternoon, with this axis of higher rates shifting south through
the afternoon and evening.

There is some potential for higher end Slight risk, or maybe even
MDT risk, probabilities along coastal areas given the expected
uptick in rainfall rates over what should be fairly saturated
ground conditions by this point. However a lack of stronger
dynamics, and lack of instability interacting with the IVT plume,
should put a cap on upward vertical motion and rainfall rates.
Thus while some flooding impacts appear likely, more widespread
significant impacts may be harder to come by, and thus not
planning on any upgrade at this time.

Pereira/Chenard

Day 3
Valid 12Z Tue Feb 04 2025 - 12Z Wed Feb 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL AND NORTHERN CALIFORNIA...

19Z Update...
No significant changes were made to the previous outlook areas.

Previous Discussion...
The atmospheric river will continue dropping southward on Tuesday,
bringing another day of moderate to heavy rainfall and some
flooding risk. Still some uncertainty with the latitude of the AR
by this time, although models do appear to be converging on a
solution covered by the Slight risk area. Some trimming on the
northern end of the Slight risk may eventually be warranted, but
with some lingering uncertainty and the saturated conditions over
that area, we were a bit conservative with the northern extent of
the risk area.

Model solutions indicate the approach of a mid level shortwave
and a stronger upper jet after 18z Tuesday. These features will
help drive an increase in IVT, and may also help briefly stall the
southward progression of the front. Thus it appears likely that we
will see an uptick in rainfall rates after 18z Tuesday from
approximately San Francisco south into Monterey county. Still some
uncertainty on the exact location of this enhanced rainfall rate
activity, as well as exactly how intense the rain will be...but
current model solutions support upwards of 1.5" in a 3 hour
period, and 2-4" in total. This rainfall will likely drive an
increase in the flood threat over these areas. Luckily most of the
heavier rainfall on the preceding days will have been north of this
corridor, so not expecting conditions to be too saturated leading
into the uptick in rain. This fact, combined with the overall
progressiveness of the system, keeps the flood risk at a Slight
level. Although will need to continue to monitor, as if rainfall
rates trend higher can not rule out a localized corridor of MDT
risk level impacts.

The Marginal risk extends further down the coast into Santa
Barbara, Ventura and Los Angeles counties. The front should be
quick moving by the time it makes it this far south, but a
quick shot of heavy rainfall is possible. The 00z GFS and NAM do
not bring the better moisture transport this far south, however the
00z ECMWF, UKMET and GEM do. Even these latter models only get
rainfall totals into the 1-2" range given the fast frontal motion.
So generally not expecting widespread or significant impacts at
this time, although rainfall rates could be briefly high enough to
result in some localized minor flood concerns. We will keep a close
eye on the sensitive burn scars over Los Angeles county, but at
this time even the more aggressive ECMWF would suggest rainfall
rates will be on the decline by the time they get that far south.
Will need to continue to monitor, but think a Marginal risk will
suffice for now.

Pereira/Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_T2bDionanPE0oyGyjoV0vbQRxmxQQV-ag-KOjcPsGMd= cGkz5f3zIx3uZM7donWQwNTIgYVMlBBVKzA4V6ou04HAdYc$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_T2bDionanPE0oyGyjoV0vbQRxmxQQV-ag-KOjcPsGMd= cGkz5f3zIx3uZM7donWQwNTIgYVMlBBVKzA4V6ouAedW-bo$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_T2bDionanPE0oyGyjoV0vbQRxmxQQV-ag-KOjcPsGMd= cGkz5f3zIx3uZM7donWQwNTIgYVMlBBVKzA4V6ouiLUlePA$=20

=3D =3D =3D
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FOUS30 KWBC 030816
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
316 AM EST Mon Feb 3 2025

Day 1
Valid 12Z Mon Feb 03 2025 - 12Z Tue Feb 04 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF NORTHERN=20 CALIFORNIA...

The atmospheric river event across much of northern California will=20
continue through the entire Day 1/Monday period. A narrow (100-200=20
mile) wide plume of rainfall rounding the northwestern periphery of=20
a broad subtropical high is also being steered around a positively=20
tilted upper level trough centered over British Columbia near the=20
northern tip of Vancouver Island. The jet stream is rounding the=20
upper level trough from the northeastern side of the trough around=20
to its west and south then ejecting around the southeastern side of=20
the trough. The trough will retrograde southwestward, allowing a=20
cutoff upper level low to form as the jet stream eventually cuts off=20
from the upper level low and maintains a trough over much of eastern=20
Canada.

The upper low will drift southwestward through 12Z Tuesday, which=20
will work to reorient the atmospheric river from its current west-to-
east to more of a southwest-to-northeast orientation. This will have=20
several ramifications: First, it will maintain the plume of rain=20
into northern California as the reorienting atmospheric river pivots=20
over this area. Rates are expected to remain largely steady based on=20
the latest HiRes guidance. Second, the "pivot" will be associated=20
with a subtle surface low tracking along the atmospheric river. This=20
will locally increase rainfall rates from midday through this=20
afternoon area-wide...though localized convergence in the northern=20 Sacramento Valley will keep rainfall rates elevated there throughout=20
the period. Third, the southwesterly flow may support the ongoing=20
low level jet in the Sacramento Valley better since the broader flow=20
will align better with the low-level jet. The result will be=20
continued heavy rain for the northern and eastern Sacramento Valley=20
and the foothills of the northern Sierras with a widespread 3-5=20
inches of rain expected.

The southwesterly reorienting will then begin to push the=20
atmospheric river southward from this afternoon through tonight,=20
reaching the Bay Area this evening. Upslope flow into the Sierras=20
will keep heavy rain ongoing into the foothills of the Sierras all=20
the way up the Sacramento Valley, however, the rain will finally=20
taper off and give the northern coastal ranges a much needed break=20
by tonight as the core of the AR moves south of the Bay Area and=20
weakens with time. The faster southerly movement of the AR from late=20
this afternoon through the overnight should significantly lower the=20
flooding threat with decreasing latitude, so the southern end of the=20
Slight risk is largely the same, stopping just north of the Bay=20
Area, as amounts from the Bay Area south should only necessitate a=20
Marginal Risk since they've been relatively dry in recent days.

With this expected evolution, a few minor changes were made to the=20
Day 1 ERO from continuity, namely to begin expanding the Marginal=20
Risk southward to include the Santa Cruz mountains through Monterey=20
Bay. Otherwise, only minor tweaks were made to better match both=20
Marginal and Slight risk areas with the local higher elevations that=20
will see mostly snow, while including some of the valleys in between.

Wegman


Day 2
Valid 12Z Tue Feb 04 2025 - 12Z Wed Feb 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL AND NORTHERN CALIFORNIA...

The atmospheric river event will continue into Tuesday across
central and northern CA. Model solutions continue to indicate the=20
approach of a mid level shortwave and a stronger upper jet after=20
18z Tuesday. The approach of these features should help slow/stall
and increase the magnitude of the IVT axis during the day. The=20
increase in forcing/IVT and a strengthening of the low level=20
convergence along the front, will both support an uptick in=20
rainfall rates from near San Francisco into the Sacramento Valley=20
and foothills of the Sierra. Hourly rainfall could approach and=20
locally exceed 0.5" along this front, which should drive an=20
increase in the flood threat. The good news is that most of these=20
areas in line for the heaviest rainfall Tuesday have been south of=20
the heaviest rain the past few days. This combined with the fact=20
that the front/IVT axis (while briefly stalling), will start to=20
make quicker southward progress by 00z, should limit the threat of=20
more widespread significant flood impacts. Nonetheless, do=20
anticipate some flooding and landslide potential to accompany this=20
rainfall Tuesday.

The Slight risk extends south into coastal Monterey county, where
stronger orographic effects will help drive heaver rainfall totals
in the 4-7" range. As the front drops into this area there will=20
also be an uptick in hourly rainfall, with high probabilities of=20
0.5" in an hour and localized totals approaching 0.75" in an hour=20
probable. Heavy rainfall is common along this corridor, and=20
antecedent conditions this far south are quite dry. Both these=20
factors should help put a cap on the magnitude of flood impacts=20
from this rain, however would still expect to see at least some=20
flood and landslide potential.

The Marginal risk extends further down the coast into Santa
Barbara, Ventura and far western Los Angeles counties. The front=20
should be quick moving by this time, and the IVT axis should be
weakening. The GFS is the weakest model, but most other models have
come around to at least a short period of locally heavy rainfall=20
getting into the favored upslope terrain areas. Even these wetter=20
models (and the WPC forecast) only get rainfall totals into the=20
1-2" range given the fast frontal motion. So generally not=20
expecting widespread or significant impacts at this time, although=20
rainfall rates could be briefly high enough to result in some=20
localized minor flood concerns.

Chenard


Day 3
Valid 12Z Wed Feb 05 2025 - 12Z Thu Feb 06 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE OHIO VALLEY...

Strong southwesterly flow will advect abundant moisture northward
into the OH Valley on Wed into Wed night, with PWs forecast to
increase over the 90th percentile for early February. Increasing
WAA, weak mid level shortwaves moving east within the quick zonal=20
flow, and upper level divergence in the right entrance region of a
jet to the north and left exit region of a strong jet over the MS=20
Valley, will broadly support an expansion of showers across the=20
region through the period. Model guidance also indicates decent=20
instability near and south of a northward moving warm front, thus=20
expect we will see embedded thunderstorms as well. Given the=20
forcing, moisture and instability forecast, do anticipate we will=20
see some locally heavy rainfall rates materialize, especially by=20
Wed evening into the overnight near the lifting warm front.

Still some uncertainty on the location of this front, with the=20
ECMWF the furthest north solution and the GFS on the southern side
of the model spread. Precipitation north of the front will likely=20
be either sleet or freezing rain, and thus the position of this
feature will be important to delineate the northern edge of the=20
flood risk area. At this time generally favor something in the=20
middle, which would favor an axis from KY into southern IN/OH and=20
into WV for the greatest rain rate potential, and the Marginal risk
encompasses these areas. However, if a warmer/further north=20
solution becomes more likely, then the Marginal may need to be=20
expanded further north, with the opposite being true if a=20
colder/south scenario comes to fruition. Portions of=20
central/eastern KY into WV have above average soil saturation and=20 streamflows, and so this area is likely most susceptible to some=20
flooding impacts if higher rainfall rates do materialize.

Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7MEWS3ioW44KEYAdH_jDGwwhI80VCMOrHDQhhrhEiOVd= SEv90Efj7x0FhRpYHHFTBlmrHiVc2ejlw3BQrBj194xEGG8$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7MEWS3ioW44KEYAdH_jDGwwhI80VCMOrHDQhhrhEiOVd= SEv90Efj7x0FhRpYHHFTBlmrHiVc2ejlw3BQrBj1uyfyeE4$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7MEWS3ioW44KEYAdH_jDGwwhI80VCMOrHDQhhrhEiOVd= SEv90Efj7x0FhRpYHHFTBlmrHiVc2ejlw3BQrBj1YutczJ0$=20

=3D =3D =3D
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FOUS30 KWBC 031532
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1032 AM EST Mon Feb 3 2025

Day 1
Valid 16Z Mon Feb 03 2025 - 12Z Tue Feb 04 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF NORTHERN CALIFORNIA...

16z update...
Observations and 12z HREF CAMs depict little changes are going to
be required for this update. Small southward adjustments and tweaks
for slight snow level changes were made, but this is more cosmetic
than substantive.=20

Gallina


~~~Prior Discussion~~~
The atmospheric river event across much of northern California will
continue through the entire Day 1/Monday period. A narrow (100-200
mile) wide plume of rainfall rounding the northwestern periphery of
a broad subtropical high is also being steered around a positively
tilted upper level trough centered over British Columbia near the
northern tip of Vancouver Island. The jet stream is rounding the
upper level trough from the northeastern side of the trough around
to its west and south then ejecting around the southeastern side of
the trough. The trough will retrograde southwestward, allowing a
cutoff upper level low to form as the jet stream eventually cuts off
from the upper level low and maintains a trough over much of eastern
Canada.

The upper low will drift southwestward through 12Z Tuesday, which
will work to reorient the atmospheric river from its current west-to-
east to more of a southwest-to-northeast orientation. This will have
several ramifications: First, it will maintain the plume of rain
into northern California as the reorienting atmospheric river pivots
over this area. Rates are expected to remain largely steady based on
the latest HiRes guidance. Second, the "pivot" will be associated
with a subtle surface low tracking along the atmospheric river. This
will locally increase rainfall rates from midday through this
afternoon area-wide...though localized convergence in the northern
Sacramento Valley will keep rainfall rates elevated there throughout
the period. Third, the southwesterly flow may support the ongoing
low level jet in the Sacramento Valley better since the broader flow
will align better with the low-level jet. The result will be
continued heavy rain for the northern and eastern Sacramento Valley
and the foothills of the northern Sierras with a widespread 3-5
inches of rain expected.

The southwesterly reorienting will then begin to push the
atmospheric river southward from this afternoon through tonight,
reaching the Bay Area this evening. Upslope flow into the Sierras
will keep heavy rain ongoing into the foothills of the Sierras all
the way up the Sacramento Valley, however, the rain will finally
taper off and give the northern coastal ranges a much needed break
by tonight as the core of the AR moves south of the Bay Area and
weakens with time. The faster southerly movement of the AR from late
this afternoon through the overnight should significantly lower the
flooding threat with decreasing latitude, so the southern end of the
Slight risk is largely the same, stopping just north of the Bay
Area, as amounts from the Bay Area south should only necessitate a
Marginal Risk since they've been relatively dry in recent days.

With this expected evolution, a few minor changes were made to the
Day 1 ERO from continuity, namely to begin expanding the Marginal
Risk southward to include the Santa Cruz mountains through Monterey
Bay. Otherwise, only minor tweaks were made to better match both
Marginal and Slight risk areas with the local higher elevations that
will see mostly snow, while including some of the valleys in between.

Wegman


Day 2
Valid 12Z Tue Feb 04 2025 - 12Z Wed Feb 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL AND NORTHERN CALIFORNIA...

The atmospheric river event will continue into Tuesday across
central and northern CA. Model solutions continue to indicate the
approach of a mid level shortwave and a stronger upper jet after
18z Tuesday. The approach of these features should help slow/stall
and increase the magnitude of the IVT axis during the day. The
increase in forcing/IVT and a strengthening of the low level
convergence along the front, will both support an uptick in
rainfall rates from near San Francisco into the Sacramento Valley
and foothills of the Sierra. Hourly rainfall could approach and
locally exceed 0.5" along this front, which should drive an
increase in the flood threat. The good news is that most of these
areas in line for the heaviest rainfall Tuesday have been south of
the heaviest rain the past few days. This combined with the fact
that the front/IVT axis (while briefly stalling), will start to
make quicker southward progress by 00z, should limit the threat of
more widespread significant flood impacts. Nonetheless, do
anticipate some flooding and landslide potential to accompany this
rainfall Tuesday.

The Slight risk extends south into coastal Monterey county, where
stronger orographic effects will help drive heaver rainfall totals
in the 4-7" range. As the front drops into this area there will
also be an uptick in hourly rainfall, with high probabilities of
0.5" in an hour and localized totals approaching 0.75" in an hour
probable. Heavy rainfall is common along this corridor, and
antecedent conditions this far south are quite dry. Both these
factors should help put a cap on the magnitude of flood impacts
from this rain, however would still expect to see at least some
flood and landslide potential.

The Marginal risk extends further down the coast into Santa
Barbara, Ventura and far western Los Angeles counties. The front
should be quick moving by this time, and the IVT axis should be
weakening. The GFS is the weakest model, but most other models have
come around to at least a short period of locally heavy rainfall
getting into the favored upslope terrain areas. Even these wetter
models (and the WPC forecast) only get rainfall totals into the
1-2" range given the fast frontal motion. So generally not
expecting widespread or significant impacts at this time, although
rainfall rates could be briefly high enough to result in some
localized minor flood concerns.

Chenard


Day 3
Valid 12Z Wed Feb 05 2025 - 12Z Thu Feb 06 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE OHIO VALLEY...

Strong southwesterly flow will advect abundant moisture northward
into the OH Valley on Wed into Wed night, with PWs forecast to
increase over the 90th percentile for early February. Increasing
WAA, weak mid level shortwaves moving east within the quick zonal
flow, and upper level divergence in the right entrance region of a
jet to the north and left exit region of a strong jet over the MS
Valley, will broadly support an expansion of showers across the
region through the period. Model guidance also indicates decent
instability near and south of a northward moving warm front, thus
expect we will see embedded thunderstorms as well. Given the
forcing, moisture and instability forecast, do anticipate we will
see some locally heavy rainfall rates materialize, especially by
Wed evening into the overnight near the lifting warm front.

Still some uncertainty on the location of this front, with the
ECMWF the furthest north solution and the GFS on the southern side
of the model spread. Precipitation north of the front will likely
be either sleet or freezing rain, and thus the position of this
feature will be important to delineate the northern edge of the
flood risk area. At this time generally favor something in the
middle, which would favor an axis from KY into southern IN/OH and
into WV for the greatest rain rate potential, and the Marginal risk
encompasses these areas. However, if a warmer/further north
solution becomes more likely, then the Marginal may need to be
expanded further north, with the opposite being true if a
colder/south scenario comes to fruition. Portions of
central/eastern KY into WV have above average soil saturation and
streamflows, and so this area is likely most susceptible to some
flooding impacts if higher rainfall rates do materialize.

Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-7pc7lILZsMqFfB8VAVc3VtTZIGNM7kTam2JJSS7Yanj= fP3CBEM5xJQdnJf5g8-IwBYWmPW0clibUXH8MKS_srzPzZE$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-7pc7lILZsMqFfB8VAVc3VtTZIGNM7kTam2JJSS7Yanj= fP3CBEM5xJQdnJf5g8-IwBYWmPW0clibUXH8MKS_NrFE4mA$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-7pc7lILZsMqFfB8VAVc3VtTZIGNM7kTam2JJSS7Yanj= fP3CBEM5xJQdnJf5g8-IwBYWmPW0clibUXH8MKS__JsZnmc$=20

=3D =3D =3D
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FOUS30 KWBC 031926
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
226 PM EST Mon Feb 3 2025

Day 1
Valid 16Z Mon Feb 03 2025 - 12Z Tue Feb 04 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF NORTHERN CALIFORNIA...

16z update...
Observations and 12z HREF CAMs depict little changes are going to
be required for this update. Small southward adjustments and tweaks
for slight snow level changes were made, but this is more cosmetic
than substantive.

Gallina


~~~Prior Discussion~~~
The atmospheric river event across much of northern California will
continue through the entire Day 1/Monday period. A narrow (100-200
mile) wide plume of rainfall rounding the northwestern periphery of
a broad subtropical high is also being steered around a positively
tilted upper level trough centered over British Columbia near the
northern tip of Vancouver Island. The jet stream is rounding the
upper level trough from the northeastern side of the trough around
to its west and south then ejecting around the southeastern side of
the trough. The trough will retrograde southwestward, allowing a
cutoff upper level low to form as the jet stream eventually cuts off
from the upper level low and maintains a trough over much of eastern
Canada.

The upper low will drift southwestward through 12Z Tuesday, which
will work to reorient the atmospheric river from its current west-to-
east to more of a southwest-to-northeast orientation. This will have
several ramifications: First, it will maintain the plume of rain
into northern California as the reorienting atmospheric river pivots
over this area. Rates are expected to remain largely steady based on
the latest HiRes guidance. Second, the "pivot" will be associated
with a subtle surface low tracking along the atmospheric river. This
will locally increase rainfall rates from midday through this
afternoon area-wide...though localized convergence in the northern
Sacramento Valley will keep rainfall rates elevated there throughout
the period. Third, the southwesterly flow may support the ongoing
low level jet in the Sacramento Valley better since the broader flow
will align better with the low-level jet. The result will be
continued heavy rain for the northern and eastern Sacramento Valley
and the foothills of the northern Sierras with a widespread 3-5
inches of rain expected.

The southwesterly reorienting will then begin to push the
atmospheric river southward from this afternoon through tonight,
reaching the Bay Area this evening. Upslope flow into the Sierras
will keep heavy rain ongoing into the foothills of the Sierras all
the way up the Sacramento Valley, however, the rain will finally
taper off and give the northern coastal ranges a much needed break
by tonight as the core of the AR moves south of the Bay Area and
weakens with time. The faster southerly movement of the AR from late
this afternoon through the overnight should significantly lower the
flooding threat with decreasing latitude, so the southern end of the
Slight risk is largely the same, stopping just north of the Bay
Area, as amounts from the Bay Area south should only necessitate a
Marginal Risk since they've been relatively dry in recent days.

With this expected evolution, a few minor changes were made to the
Day 1 ERO from continuity, namely to begin expanding the Marginal
Risk southward to include the Santa Cruz mountains through Monterey
Bay. Otherwise, only minor tweaks were made to better match both
Marginal and Slight risk areas with the local higher elevations that
will see mostly snow, while including some of the valleys in between.

Wegman


Day 2
Valid 12Z Tue Feb 04 2025 - 12Z Wed Feb 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL AND NORTHERN CALIFORNIA...

...1930 UTC Update...
Minimal changes made to the Day 2 ERO, based on the latest (12Z)
guidance, including the high-res CAMs. The Slight Risk continues to
incorporate the HREF's highest probabilities (>40%) of 0.50"+/hr
rainfall rates.=20

Hurley

...Discussion...
The atmospheric river event will continue into Tuesday across=20
central and northern CA. Model solutions continue to indicate the=20
approach of a mid level shortwave and a stronger upper jet after=20
18z Tuesday. The approach of these features should help slow/stall=20
and increase the magnitude of the IVT axis during the day. The=20
increase in forcing/IVT and a strengthening of the low level=20
convergence along the front, will both support an uptick in=20
rainfall rates from near San Francisco into the Sacramento Valley=20
and foothills of the Sierra. Hourly rainfall could approach and=20
locally exceed 0.5" along this front, which should drive an=20
increase in the flood threat. The good news is that most of these=20
areas in line for the heaviest rainfall Tuesday have been south of=20
the heaviest rain the past few days. This combined with the fact=20
that the front/IVT axis (while briefly stalling), will start to=20
make quicker southward progress by 00z, should limit the threat of=20
more widespread significant flood impacts. Nonetheless, do=20
anticipate some flooding and landslide potential to accompany this=20
rainfall Tuesday.

The Slight risk extends south into coastal Monterey county, where
stronger orographic effects will help drive heaver rainfall totals
in the 4-7" range. As the front drops into this area there will
also be an uptick in hourly rainfall, with high probabilities of
0.5" in an hour and localized totals approaching 0.75" in an hour
probable. Heavy rainfall is common along this corridor, and
antecedent conditions this far south are quite dry. Both these
factors should help put a cap on the magnitude of flood impacts
from this rain, however would still expect to see at least some
flood and landslide potential.

The Marginal risk extends further down the coast into Santa
Barbara, Ventura and far western Los Angeles counties. The front
should be quick moving by this time, and the IVT axis should be
weakening. The GFS is the weakest model, but most other models have
come around to at least a short period of locally heavy rainfall
getting into the favored upslope terrain areas. Even these wetter
models (and the WPC forecast) only get rainfall totals into the
1-2" range given the fast frontal motion. So generally not
expecting widespread or significant impacts at this time, although
rainfall rates could be briefly high enough to result in some
localized minor flood concerns.

Chenard


Day 3
Valid 12Z Wed Feb 05 2025 - 12Z Thu Feb 06 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE OHIO VALLEY...

...1930 UTC Update...
Have pared the Marginal Risk area significantly across the OH
Valley, specifically the northern and eastern portions (no longer
including WV and southwest PA), based on the latest deterministic
and probabilistic ice/freezing rain forecast, along with the=20
forecast deep-layer instability. The Marginal Risk area now across=20
much of western KY into southern IN and far southwest OH is outside
of the ice accretion zone (though some light glazing is possible=20
early). Within this area, elevated MUCAPEs around 500 to 750 J/Kg=20
may produce 0.50-0.75"/hr and ~1.5"/3hr rates, which could allow=20
for localized runoff issues. The latest (12Z) deterministic ECMWF
lines up fairly well with the adjusted Marginal Risk area.

Hurley

...Previous Discussion...
Strong southwesterly flow will advect abundant moisture northward=20
into the OH Valley on Wed into Wed night, with PWs forecast to=20
increase over the 90th percentile for early February. Increasing=20
WAA, weak mid level shortwaves moving east within the quick zonal=20
flow, and upper level divergence in the right entrance region of a=20
jet to the north and left exit region of a strong jet over the MS=20
Valley, will broadly support an expansion of showers across the=20
region through the period. Model guidance also indicates decent=20
instability near and south of a northward moving warm front, thus=20
expect we will see embedded thunderstorms as well. Given the=20
forcing, moisture and instability forecast, do anticipate we will=20
see some locally heavy rainfall rates materialize, especially by=20
Wed evening into the overnight near the lifting warm front.

Still some uncertainty on the location of this front, with the
ECMWF the furthest north solution and the GFS on the southern side
of the model spread. Precipitation north of the front will likely
be either sleet or freezing rain, and thus the position of this
feature will be important to delineate the northern edge of the
flood risk area. At this time generally favor something in the
middle, which would favor an axis from KY into southern IN/OH and
into WV for the greatest rain rate potential, and the Marginal risk
encompasses these areas. However, if a warmer/further north
solution becomes more likely, then the Marginal may need to be
expanded further north, with the opposite being true if a
colder/south scenario comes to fruition. Portions of
central/eastern KY into WV have above average soil saturation and
streamflows, and so this area is likely most susceptible to some
flooding impacts if higher rainfall rates do materialize.

Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-P-nAzM9T-uDazEVDdaOilZ5I4kPYsnEpw_7zmYx2Qax= xok_83DmbRwjrtdJLwpmUUBHJ8dzeNjcWFk-XHbBnjPYrJ4$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-P-nAzM9T-uDazEVDdaOilZ5I4kPYsnEpw_7zmYx2Qax= xok_83DmbRwjrtdJLwpmUUBHJ8dzeNjcWFk-XHbBAUuaM54$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-P-nAzM9T-uDazEVDdaOilZ5I4kPYsnEpw_7zmYx2Qax= xok_83DmbRwjrtdJLwpmUUBHJ8dzeNjcWFk-XHbBsWsQv_c$=20

=3D =3D =3D
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FOUS30 KWBC 040021
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
721 PM EST Mon Feb 3 2025

Day 1
Valid 01Z Tue Feb 04 2025 - 12Z Tue Feb 04 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF NORTHERN CALIFORNIA...

16z update...
Observations and trends seen in radar imagery through late
afternoon suggested a subtle southward expansion of the Slight Risk
area was needed across portions of the Sacramento Valle where
there was a region of enhanced moisture flux convergence where=20
20 to 35 knot south to southeasterly surface winds encounter the
terrain and a quasi- stationary front draped across the region. The
enhanced convergence and upper level support has once again
resulted in a region of enhanced rainfall rates embedded within a
broader more steady rainfall...raising the possibility of rainfall
rates creeping above half inch per hour over areas that have
already received multiple inches of rainfall recently. Except for=20
the small southward adjustments and tweaks...changes were made, but
this is more cosmetic than substantive.

Bann


~~~Prior Discussion~~~
The atmospheric river event across much of northern California will
continue through the entire Day 1/Monday period. A narrow (100-200
mile) wide plume of rainfall rounding the northwestern periphery of
a broad subtropical high is also being steered around a positively
tilted upper level trough centered over British Columbia near the
northern tip of Vancouver Island. The jet stream is rounding the
upper level trough from the northeastern side of the trough around
to its west and south then ejecting around the southeastern side of
the trough. The trough will retrograde southwestward, allowing a
cutoff upper level low to form as the jet stream eventually cuts off
from the upper level low and maintains a trough over much of eastern
Canada.

The upper low will drift southwestward through 12Z Tuesday, which
will work to reorient the atmospheric river from its current west-to-
east to more of a southwest-to-northeast orientation. This will have
several ramifications: First, it will maintain the plume of rain
into northern California as the reorienting atmospheric river pivots
over this area. Rates are expected to remain largely steady based on
the latest HiRes guidance. Second, the "pivot" will be associated
with a subtle surface low tracking along the atmospheric river. This
will locally increase rainfall rates from midday through this
afternoon area-wide...though localized convergence in the northern
Sacramento Valley will keep rainfall rates elevated there throughout
the period. Third, the southwesterly flow may support the ongoing
low level jet in the Sacramento Valley better since the broader flow
will align better with the low-level jet. The result will be
continued heavy rain for the northern and eastern Sacramento Valley
and the foothills of the northern Sierras with a widespread 3-5
inches of rain expected.

The southwesterly reorienting will then begin to push the
atmospheric river southward from this afternoon through tonight,
reaching the Bay Area this evening. Upslope flow into the Sierras
will keep heavy rain ongoing into the foothills of the Sierras all
the way up the Sacramento Valley, however, the rain will finally
taper off and give the northern coastal ranges a much needed break
by tonight as the core of the AR moves south of the Bay Area and
weakens with time. The faster southerly movement of the AR from late
this afternoon through the overnight should significantly lower the
flooding threat with decreasing latitude, so the southern end of the
Slight risk is largely the same, stopping just north of the Bay
Area, as amounts from the Bay Area south should only necessitate a
Marginal Risk since they've been relatively dry in recent days.

With this expected evolution, a few minor changes were made to the
Day 1 ERO from continuity, namely to begin expanding the Marginal
Risk southward to include the Santa Cruz mountains through Monterey
Bay. Otherwise, only minor tweaks were made to better match both
Marginal and Slight risk areas with the local higher elevations that
will see mostly snow, while including some of the valleys in between.

Wegman


Day 2
Valid 12Z Tue Feb 04 2025 - 12Z Wed Feb 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL AND NORTHERN CALIFORNIA...

...1930 UTC Update...
Minimal changes made to the Day 2 ERO, based on the latest (12Z)
guidance, including the high-res CAMs. The Slight Risk continues to
incorporate the HREF's highest probabilities (>40%) of 0.50"+/hr
rainfall rates.

Hurley

...Discussion...
The atmospheric river event will continue into Tuesday across
central and northern CA. Model solutions continue to indicate the
approach of a mid level shortwave and a stronger upper jet after
18z Tuesday. The approach of these features should help slow/stall
and increase the magnitude of the IVT axis during the day. The
increase in forcing/IVT and a strengthening of the low level
convergence along the front, will both support an uptick in
rainfall rates from near San Francisco into the Sacramento Valley
and foothills of the Sierra. Hourly rainfall could approach and
locally exceed 0.5" along this front, which should drive an
increase in the flood threat. The good news is that most of these
areas in line for the heaviest rainfall Tuesday have been south of
the heaviest rain the past few days. This combined with the fact
that the front/IVT axis (while briefly stalling), will start to
make quicker southward progress by 00z, should limit the threat of
more widespread significant flood impacts. Nonetheless, do
anticipate some flooding and landslide potential to accompany this
rainfall Tuesday.

The Slight risk extends south into coastal Monterey county, where
stronger orographic effects will help drive heaver rainfall totals
in the 4-7" range. As the front drops into this area there will
also be an uptick in hourly rainfall, with high probabilities of
0.5" in an hour and localized totals approaching 0.75" in an hour
probable. Heavy rainfall is common along this corridor, and
antecedent conditions this far south are quite dry. Both these
factors should help put a cap on the magnitude of flood impacts
from this rain, however would still expect to see at least some
flood and landslide potential.

The Marginal risk extends further down the coast into Santa
Barbara, Ventura and far western Los Angeles counties. The front
should be quick moving by this time, and the IVT axis should be
weakening. The GFS is the weakest model, but most other models have
come around to at least a short period of locally heavy rainfall
getting into the favored upslope terrain areas. Even these wetter
models (and the WPC forecast) only get rainfall totals into the
1-2" range given the fast frontal motion. So generally not
expecting widespread or significant impacts at this time, although
rainfall rates could be briefly high enough to result in some
localized minor flood concerns.

Chenard


Day 3
Valid 12Z Wed Feb 05 2025 - 12Z Thu Feb 06 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE OHIO VALLEY...

...1930 UTC Update...
Have pared the Marginal Risk area significantly across the OH
Valley, specifically the northern and eastern portions (no longer
including WV and southwest PA), based on the latest deterministic
and probabilistic ice/freezing rain forecast, along with the
forecast deep-layer instability. The Marginal Risk area now across
much of western KY into southern IN and far southwest OH is outside
of the ice accretion zone (though some light glazing is possible
early). Within this area, elevated MUCAPEs around 500 to 750 J/Kg
may produce 0.50-0.75"/hr and ~1.5"/3hr rates, which could allow
for localized runoff issues. The latest (12Z) deterministic ECMWF
lines up fairly well with the adjusted Marginal Risk area.

Hurley

...Previous Discussion...
Strong southwesterly flow will advect abundant moisture northward
into the OH Valley on Wed into Wed night, with PWs forecast to
increase over the 90th percentile for early February. Increasing
WAA, weak mid level shortwaves moving east within the quick zonal
flow, and upper level divergence in the right entrance region of a
jet to the north and left exit region of a strong jet over the MS
Valley, will broadly support an expansion of showers across the
region through the period. Model guidance also indicates decent
instability near and south of a northward moving warm front, thus
expect we will see embedded thunderstorms as well. Given the
forcing, moisture and instability forecast, do anticipate we will
see some locally heavy rainfall rates materialize, especially by
Wed evening into the overnight near the lifting warm front.

Still some uncertainty on the location of this front, with the
ECMWF the furthest north solution and the GFS on the southern side
of the model spread. Precipitation north of the front will likely
be either sleet or freezing rain, and thus the position of this
feature will be important to delineate the northern edge of the
flood risk area. At this time generally favor something in the
middle, which would favor an axis from KY into southern IN/OH and
into WV for the greatest rain rate potential, and the Marginal risk
encompasses these areas. However, if a warmer/further north
solution becomes more likely, then the Marginal may need to be
expanded further north, with the opposite being true if a
colder/south scenario comes to fruition. Portions of
central/eastern KY into WV have above average soil saturation and
streamflows, and so this area is likely most susceptible to some
flooding impacts if higher rainfall rates do materialize.

Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-PEMnVr0PxNonOBozop0PbtApwWFZDb1XKExKYQbFNQ5= yzgIyyJrgaWmkTptNk-3GPchpYh-5hqFUgpKzEVsNPpP7GY$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-PEMnVr0PxNonOBozop0PbtApwWFZDb1XKExKYQbFNQ5= yzgIyyJrgaWmkTptNk-3GPchpYh-5hqFUgpKzEVsLxzVYpI$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-PEMnVr0PxNonOBozop0PbtApwWFZDb1XKExKYQbFNQ5= yzgIyyJrgaWmkTptNk-3GPchpYh-5hqFUgpKzEVsSqJcnX8$=20

=3D =3D =3D
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FOUS30 KWBC 050824
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
324 AM EST Wed Feb 5 2025

Day 1
Valid 12Z Wed Feb 05 2025 - 12Z Thu Feb 06 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF=20
THE OHIO VALLEY...

No significant changes were made to the Marginal Risk area across=20
the Ohio Valley. Warm advection showers are expected to break out=20
over Kentucky, that with the infusion of upper level support and=20
increasing instability, will allow embedded convection to develop=20
this afternoon and evening. As the moisture plume turns the front=20
into a warm front over the Tennessee Valley this evening, expect the=20 addition of upslope into West Virginia to resulting locally=20
heavier rainfall in the favored areas. Any thunderstorms will be=20
capable of rainfall rates to 1.5 inches per hour. Soils in this=20
area remain nearly saturated and rivers are running high from the=20
rainfall event a few days ago. Thus, the additional rainfall=20
forecast today and tonight, even though amounts will likely be=20
lesser, may still cause isolated flash flooding.

Wegman


Day 2
Valid 12Z Thu Feb 06 2025 - 12Z Fri Feb 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE OHIO VALLEY AND CALIFORNIA...

...OH Valley...
Another round of locally heavy rain is expected Thursday across
portions of KY, TN, WV and far western VA along and ahead of an=20
approaching cold front. Showers and embedded thunderstorms will
likely be ongoing at 12z and may periodically continue through the
day/evening near the only slowly southward shifting front. While
nothing significant, CAPE upwards of 500-1000 j/kg still seems
likely along this corridor, which should be enough to support=20
locally heavy rainfall rates. While soil conditions and=20
streamflows are returning closer to average after the flooding=20
several days ago, some of this region is still likely more=20
sensitive than normal to additional heavy rainfall. The latest WPC=20
QPF is generally 0.75"-1", with two day totals locally exceeding=20
1.5". Given the instability forecast, it seems reasonable that we=20
will see isolated totals over 2". While the 00z GEM Reg and FV3LAM=20
are probably too high with totals, they both do suggest that if=20
convective coverage can increase enough then some 2-3" amounts can
not be ruled out. Overall expect this rainfall to pose a localized
flood risk.

...California...
After a one day break another system is forecast to move into CA
on Thursday. This is expected to be a pretty dynamic system, with a
strong mid level shortwave and upper level jet. These dynamics
should support a short duration period of enhanced rainfall
rates...although the quick forward motion of the system will limit
overall rainfall magnitudes. Recent model runs are showing some=20
uptick in rainfall amounts with this system over northern CA, but
still generally looking at totals in the 1-2" range. Given the
saturated conditions and brief potential for higher rates between=20
00z and 06z, this may be approaching Slight risk levels. Although=20
will hold off for now as the short duration of these higher rates=20
may limit the magnitude/coverage of impacts just enough to keep the
risk at Marginal.

The Marginal risk extends southward into Santa Barbara, Ventura and
Los Angeles counties as well. Less rainfall forecast here, but
there is an uptick in IVT into the terrain Thursday night, and PWs
do increase towards and just over 1". Larger scale forcing
generally shears off to the north, but the combination of
increasing PWs, IVT and upslope flow should be enough to result in
a period of moderate to locally heavy rain. We are beginning to=20
see a slow uptick in rainfall amounts in the models, and so=20
localized flood impacts are certainly a possibility. Although=20
given the overall weakening of the system and very little to no=20
instability, rainfall rates will probably only be high enough to=20
result in a minor flood risk over just the most sensitive urban=20
areas or recent burn scar locations.

Chenard

Day 3
Valid 12Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_vyJnKCbfEeTa4_SXMeTNkDiekkRwMmNFLo_cFtdZn0B= sx5LHbUwu6Wlo5zo7PreadxFuB3zXgERg3zjtyPieDcpSUg$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_vyJnKCbfEeTa4_SXMeTNkDiekkRwMmNFLo_cFtdZn0B= sx5LHbUwu6Wlo5zo7PreadxFuB3zXgERg3zjtyPitcYf0qk$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_vyJnKCbfEeTa4_SXMeTNkDiekkRwMmNFLo_cFtdZn0B= sx5LHbUwu6Wlo5zo7PreadxFuB3zXgERg3zjtyPijRF11E4$=20

=3D =3D =3D
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FOUS30 KWBC 060826
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
326 AM EST Thu Feb 6 2025

Day 1
Valid 12Z Thu Feb 06 2025 - 12Z Fri Feb 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF CALIFORNIA AND THE OHIO VALLEY...

...California...
After a one day break another system is forecast to move into CA
today and Thursday night. Not an AR but rather a compact, dynamic=20
system with a vigorous mid level shortwave and strong left exit=20
region upper level jet forcing. These dynamics should support a=20
short duration period of enhanced rainfall rates, although the=20
quick forward motion of the system will limit overall rainfall=20
magnitudes. Given the low-level ageostrophic response ahead of the=20
upper level jet streak, the latest (00Z) GEFS output shows a quick=20
uptick in southwesterly 850-700 mb moisture transport, peaking=20
between 3-4 standard deviations above normal across the central 2/3
of CA Thursday afternoon and evening. Recent model runs continue=20
to show 1-2+ inches falling mostly within 12 hours, with localized=20
amounts of 3+ inches over the coastal ranges and Sierra foothills=20
per the latest high-res guidance. Given the saturated conditions=20
and brief potential for higher rates (0.35+ in/hr) beginning around
21Z along the coast and by 00Z farther inland, this may result in=20
localized runoff issues, especially over burn scars across Santa=20
Barbara, Ventura, and Los Angeles counties.=20

...TN-OH Valleys into the Western Appalachians...
Another round of locally heavy rain is expected Thursday across=20
portions of KY, TN, WV and far western VA- NC along and ahead of an
approaching cold front. Showers and embedded thunderstorms will be
ongoing to start the period (12Z Thu) and may periodically=20
continue through the day/evening near the only slowly southward=20
shifting front. While nothing significant, CAPE upwards of 500-1000
J/Kg still seems likely along this corridor, which should be=20
enough to support locally heavy rainfall rates. While soil=20
conditions and streamflows are returning closer to average after=20
the flooding several days ago, some of this region is still likely=20
more sensitive than normal to additional heavy rainfall. The latest
WPC areal-average QPF peaks between 0.75"-1.25", though per the=20
CAMs, localized totals between 2-3"+ are expected, which makes=20
sense given the instability forecast. Overall expect this rainfall=20
to pose a localized flood risk.

Hurley


Day 2
Valid 12Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 3
Valid 12Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4vunSW8FBHhu_a6Lwa6pKE_JxY_VF8MCF3WyTc9hk8L0= PaVxe2vKPBT8B9X0K7U45N1nrvzpERIWXJZ_UwLL1kGIJTU$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4vunSW8FBHhu_a6Lwa6pKE_JxY_VF8MCF3WyTc9hk8L0= PaVxe2vKPBT8B9X0K7U45N1nrvzpERIWXJZ_UwLLhHnNuow$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4vunSW8FBHhu_a6Lwa6pKE_JxY_VF8MCF3WyTc9hk8L0= PaVxe2vKPBT8B9X0K7U45N1nrvzpERIWXJZ_UwLLX88UgJ8$=20

=3D =3D =3D
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FOUS30 KWBC 061544
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1044 AM EST Thu Feb 6 2025

Day 1
Valid 12Z Thu Feb 06 2025 - 12Z Fri Feb 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF CALIFORNIA AND THE OHIO VALLEY...

...California...

16z update...No changes were made to the Marginal Risk as 12z Hi-
Res and HREF guidance remains on track for heavy rainfall risk. For
a more detailed discussion please refer to Mesoscale Precipitation
Discussion (MPD) 23 that is valid until 03z this evening.=20

Gallina

---Prior Discussion---
After a one day break another system is=20
forecast to move into CA today and Thursday night. Not an AR but=20
rather a compact, dynamic system with a vigorous mid level=20
shortwave and strong left exit region upper level jet forcing.=20
These dynamics should support a short duration period of enhanced=20
rainfall rates, although the quick forward motion of the system=20
will limit overall rainfall magnitudes. Given the low-level=20
ageostrophic response ahead of the upper level jet streak, the=20
latest (00Z) GEFS output shows a quick uptick in southwesterly=20
850-700 mb moisture transport, peaking between 3-4 standard=20
deviations above normal across the central 2/3 of CA Thursday=20
afternoon and evening. Recent model runs continue to show 1-2+=20
inches falling mostly within 12 hours, with localized amounts of=20
3+ inches over the coastal ranges and Sierra foothills per the=20
latest high-res guidance. Given the saturated conditions and brief
potential for higher rates (0.35+ in/hr) beginning around 21Z=20
along the coast and by 00Z farther inland, this may result in=20
localized runoff issues, especially over burn scars across Santa=20
Barbara, Ventura, and Los Angeles counties.

Hurley

...TN-OH Valleys into the Western Appalachians...

16z update...Ongoing convection is starting to sag southward across
southern KY into far southern WV and far western VA. This activity
is expected to continue until about 18-19z as forcing slides past
well to the northwest and activity becomes further displaced from
pool of remaining unstable (750-1000 J/kg of SBCAPE) along the=20
western and central KY/TN boarder. As such, the Marginal Risk was=20
trimmed across much of northern KY and WV; though a second round of
scattered thunderstorms is expected this evening just north/along=20
the KY/TN border and south across Middle and eastern TN this=20
evening. Similar 1.5"+/hr rates and occasional training/repeat=20
environment crossing lower FFG and fairly saturated upper soil=20
conditions mainly across the Cumberland Plateau into the=20
Appalachians warrants maintaining the Marginal Risk here, as well.

Gallina=20

---Prior Discussion---
Another round of locally heavy rain is expected Thursday across
portions of KY, TN, WV and far western VA- NC along and ahead of an
approaching cold front. Showers and embedded thunderstorms will be
ongoing to start the period (12Z Thu) and may periodically
continue through the day/evening near the only slowly southward
shifting front. While nothing significant, CAPE upwards of 500-1000
J/Kg still seems likely along this corridor, which should be
enough to support locally heavy rainfall rates. While soil
conditions and streamflows are returning closer to average after
the flooding several days ago, some of this region is still likely
more sensitive than normal to additional heavy rainfall. The latest
WPC areal-average QPF peaks between 0.75"-1.25", though per the
CAMs, localized totals between 2-3"+ are expected, which makes
sense given the instability forecast. Overall expect this rainfall
to pose a localized flood risk.

Hurley


Day 2
Valid 12Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 3
Valid 12Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4V_2o-VrdgoefAN0qwnObY97mbMTsixOxIQHhh1tm8Z5= jlnxhLyOCATynrTEG6LWGh8ZaxnH5dKuflBrKW5-7BLpE-c$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4V_2o-VrdgoefAN0qwnObY97mbMTsixOxIQHhh1tm8Z5= jlnxhLyOCATynrTEG6LWGh8ZaxnH5dKuflBrKW5-zQCR3ZA$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4V_2o-VrdgoefAN0qwnObY97mbMTsixOxIQHhh1tm8Z5= jlnxhLyOCATynrTEG6LWGh8ZaxnH5dKuflBrKW5-KVIg0jg$=20

=3D =3D =3D
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FOUS30 KWBC 070054
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
754 PM EST Thu Feb 6 2025

Day 1
Valid 01Z Fri Feb 07 2025 - 12Z Fri Feb 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF CALIFORNIA AND THE OHIO VALLEY...

...California...
A compact, dynamic system with a vigorous mid level shortwave and=20
strong left exit region upper level jet forcing should support a=20
short duration period of enhanced rainfall rates, although the=20
quick forward motion of the system will limit overall rainfall=20
magnitudes. Given the low-level ageostrophic response ahead of the=20
upper level jet streak, the latest (00Z) GEFS output shows a quick=20
uptick in southwesterly 850-700 mb moisture transport, peaking=20
between 3-4 standard deviations above normal across the central 2/3
of CA Thursday afternoon and evening. Recent model runs continue=20
to show 1-2+ inches falling mostly within 12 hours, with localized=20
amounts of 3+ inches over the coastal ranges and Sierra foothills=20
per the latest high-res guidance. Given the saturated conditions=20
and brief potential for higher rates (0.35+ in/hr) beginning around
21Z along the coast and by 00Z farther inland, this may result in=20
localized runoff issues, especially over burn scars across Santa=20
Barbara, Ventura, and Los Angeles counties.

Gallina/Hurley


...TN Valley into the Southern Appalachians...
A round of locally heavy rain is in progress across portions of=20
KY, TN, WV and southwest VA near and ahead of an approaching cold=20
front and near the base of a broad shortwave transiting the Great=20
Lakes. While precipitable water values are run of the mill --=20
0.75-1.25" -- the coolness of the atmosphere is leading to=20
significant saturation, which is aiding precipitation efficiency.=20
ML CAPE of 500-1000 J/Kg is being tapped by increasingly surface=20
based convection closer to the front. Thus far, hourly rain totals
have maximized in the 0.5-1" range. Given the ingredients above,=20
hourly rain totals to 1.5" and local amounts of 3" remain=20
possible over the next several hours. The decreasing size of the
rainfall pattern with time suggests a decline in the risk as we
move through the overnight hours. Some of this region (the=20
northeast portion of the Marginal Risk) is more sensitive than=20
normal to additional heavy rainfall given the 2-4" that fell over=20
the past 24 hours. Overall, an isolated to widely scattered flash=20
flood risk appears to exist now that the convective pattern is=20
narrowing and showing increasing progression. The overall excessive
rainfall risk is expected to end during the early morning hours of
Friday across northern GA, roughly 07z-08z based on the 18z HREF=20 probabilities of 0.5"+ in an hour.

Roth


Day 2
Valid 12Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Pereira


Day 3
Valid 12Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Pereira


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5N0OJCaTCcemOWB2l6MO6NFFGHD58ya-2S0lif4zwfgo= RpAk83uTGBrCCORYno9FV2l31y2XLPvBOdi0DYgW9wtrXIw$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5N0OJCaTCcemOWB2l6MO6NFFGHD58ya-2S0lif4zwfgo= RpAk83uTGBrCCORYno9FV2l31y2XLPvBOdi0DYgWeh_0ol8$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5N0OJCaTCcemOWB2l6MO6NFFGHD58ya-2S0lif4zwfgo= RpAk83uTGBrCCORYno9FV2l31y2XLPvBOdi0DYgWKXHym70$=20

=3D =3D =3D
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FOUS30 KWBC 071911
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
211 PM EST Fri Feb 7 2025

Day 1
Valid 16Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Churchill/Hurley


Day 2
Valid 12Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025

West Virginia...
An approaching frontal wave is expected to bring precipitable water
values up above an inch into WV. While 1000-500 hPa thickness
values are higher when compared to Thursday's rainfall farther
south, implying slightly less atmospheric saturation, the=20
combination of 50+ kts of 850 hPa inflow into WV along with ~100=20
J/kg of CAPE and the forecast precipitable water values should be=20
sufficient for hourly rain totals of 0.5"+, even though this is not
advertised in the 12z HREF. The three hour flash flood guidance=20
values are so low (around 1") that those values could be exceeded=20
with two hours of such rains. Since soils there are saturated, and=20
the terrain is rugged, opted to add a Marginal Risk area for much=20
of WV (outside of its northern or eastern Panhandles) in=20
coordination with the Charleston WV forecast office. This also=20
helps support their and Blacksburg VA's new flood watch.

Roth



Day 3
Valid 12Z Sun Feb 09 2025 - 12Z Mon Feb 10 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Roth/Hurley


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-UMz4AYvTejp91PnIK_8qvZtWnv5ULTQKW95D8O_rchS= Ww37ihkDJBeAkYqd0Kv0vCwhGTYzqA95_XGxExuk8yJDBLE$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-UMz4AYvTejp91PnIK_8qvZtWnv5ULTQKW95D8O_rchS= Ww37ihkDJBeAkYqd0Kv0vCwhGTYzqA95_XGxExukslJIhoY$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-UMz4AYvTejp91PnIK_8qvZtWnv5ULTQKW95D8O_rchS= Ww37ihkDJBeAkYqd0Kv0vCwhGTYzqA95_XGxExuk5cT6mEE$=20

=3D =3D =3D
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FOUS30 KWBC 081620
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1120 AM EST Sat Feb 8 2025

Day 1
Valid 16Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025

...16Z Update...

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF WEST
VIRGINIA...

No changes were made to the ongoing Marginal Risk area across West
Virginia. Recent rainfall has made the soils there saturated.
However, rainfall rates have all been at a half inch per hour or
less across the area. Thus, any flooding has been from areal river
rises as rates have not been high enough to cause flash flooding.=20
A slow-moving warm front in the area has been the cause for the
rainfall. The rain will lift north this afternoon as the state gets
into the warm sector. This evening, the cold front will move
through that could cause heavier rain, albeit with fast moving
convection. The greatest threat for isolated flash flooding will
occur with any training heavier showers, and a thunderstorm or two
can't be ruled out. The front will sweep through by around
midnight, ending the flooding threat due to rainfall, though rises
from draining streams and creeks will continue through the night
and into the day on Sunday.

Wegman

...Previous Discussion...

...West Virginia...
Strong N-S quasi-zonal mid and upper level flow will be perturbed
a bit during Day 1 (12Z Sat-12Z Sun) as a 150+ kt upper level jet
streak traverses the Upper Midwest and Ohio Valley, while a flat
500 mb vort lobe pushes across the Lower Great Lakes. Broad-scale
exit region forcing associated with the upper jet axis will surge
southwesterly low-level inflow ahead of the surface frontal wave,
with 850 mb moisture flux anomalies peaking between 4-5 standard
deviations above normal later this afternoon into Sat night, while
TPW values peak around 1". Robust synoptic-scale support and low-
level moisture transport will be offset somewhat by the weak
elevated instability, with MUCAPEs generally less than 500 J/Kg.
Nevertheless, even though not advertised on the latest (00Z Sat)
HREF, the aforementioned dynamic and thermodynamic ingredients will
be sufficient for spotty hourly rain rates of 0.5"+ and 3-hourly
rates of 1.0"+, with localized event totals between 1.5-2.0"+.

Current 3-hr flash flood guidance values remain quite low (1" or
less) across the outlook area, which includes much of WV. Despite
the lack of instability, the low FFG values could be exceeded over
isolated areas with 2 consecutive hours of 0.5"+/hr rainfall rates.
Since the soils in these areas are saturated, and the terrain is
rugged, we have maintained the Marginal Risk area for much of WV
(outside of its northern or eastern Panhandles).

Hurley/Roth


Day 2
Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 3
Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_wpVgPxceCQIFJzmauGsUpxBAle7w4NYreTL8EgxZ0Cu= 7hOgiuIOYdQQ33amqaHE2rydU5Yu0wRLWcP22GFjhE3-_vk$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_wpVgPxceCQIFJzmauGsUpxBAle7w4NYreTL8EgxZ0Cu= 7hOgiuIOYdQQ33amqaHE2rydU5Yu0wRLWcP22GFjNKKDAzE$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_wpVgPxceCQIFJzmauGsUpxBAle7w4NYreTL8EgxZ0Cu= 7hOgiuIOYdQQ33amqaHE2rydU5Yu0wRLWcP22GFjepJsK48$=20

=3D =3D =3D
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FOUS30 KWBC 082015
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
315 PM EST Sat Feb 8 2025

Day 1
Valid 16Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025

...16Z Update...

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF WEST
VIRGINIA...

No changes were made to the ongoing Marginal Risk area across West
Virginia. Recent rainfall has made the soils there saturated.
However, rainfall rates have all been at a half inch per hour or
less across the area. Thus, any flooding has been from areal river
rises as rates have not been high enough to cause flash flooding.
A slow-moving warm front in the area has been the cause for the
rainfall. The rain will lift north this afternoon as the state gets
into the warm sector. This evening, the cold front will move
through that could cause heavier rain, albeit with fast moving
convection. The greatest threat for isolated flash flooding will
occur with any training heavier showers, and a thunderstorm or two
can't be ruled out. The front will sweep through by around
midnight, ending the flooding threat due to rainfall, though rises
from draining streams and creeks will continue through the night
and into the day on Sunday.

Wegman

...Previous Discussion...

...West Virginia...
Strong N-S quasi-zonal mid and upper level flow will be perturbed
a bit during Day 1 (12Z Sat-12Z Sun) as a 150+ kt upper level jet
streak traverses the Upper Midwest and Ohio Valley, while a flat
500 mb vort lobe pushes across the Lower Great Lakes. Broad-scale
exit region forcing associated with the upper jet axis will surge
southwesterly low-level inflow ahead of the surface frontal wave,
with 850 mb moisture flux anomalies peaking between 4-5 standard
deviations above normal later this afternoon into Sat night, while
TPW values peak around 1". Robust synoptic-scale support and low-
level moisture transport will be offset somewhat by the weak
elevated instability, with MUCAPEs generally less than 500 J/Kg.
Nevertheless, even though not advertised on the latest (00Z Sat)
HREF, the aforementioned dynamic and thermodynamic ingredients will
be sufficient for spotty hourly rain rates of 0.5"+ and 3-hourly
rates of 1.0"+, with localized event totals between 1.5-2.0"+.

Current 3-hr flash flood guidance values remain quite low (1" or
less) across the outlook area, which includes much of WV. Despite
the lack of instability, the low FFG values could be exceeded over
isolated areas with 2 consecutive hours of 0.5"+/hr rainfall rates.
Since the soils in these areas are saturated, and the terrain is
rugged, we have maintained the Marginal Risk area for much of WV
(outside of its northern or eastern Panhandles).

Hurley/Roth


Day 2
Valid 12Z Sun Feb 09 2025 - 12Z Mon Feb 10 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Pereira


Day 3
Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Pereira


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-pDEXQQSpZOHzi4YeF6tjVSu9n_I-DQW6DG-c1Qi_X8_= f14OTTRQvycB7v5knsjZJyIaM2deIuv9h600YDEW3dsoPvg$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-pDEXQQSpZOHzi4YeF6tjVSu9n_I-DQW6DG-c1Qi_X8_= f14OTTRQvycB7v5knsjZJyIaM2deIuv9h600YDEWgfLQHEo$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-pDEXQQSpZOHzi4YeF6tjVSu9n_I-DQW6DG-c1Qi_X8_= f14OTTRQvycB7v5knsjZJyIaM2deIuv9h600YDEWKkmyRGs$=20

=3D =3D =3D
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FOUS30 KWBC 090100
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
800 PM EST Sat Feb 8 2025

Day 1
Valid 01Z Sun Feb 09 2025 - 12Z Sun Feb 09 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF=20
WEST VIRGINIA...

01Z Update...
Given the antecedent soil conditions and ongoing flooding issues,=20
a Marginal Risk was left in place across portions of eastern and
southern West Virginia. Radar shows showers developing along and=20
ahead of a cold front, including a narrow line of more intense=20
showers developing along the front as it advances across central=20
Kentucky this hour. These showers are advancing quickly to the=20
east, keeping accumulations in check, however sufficient moisture=20
and forcing, along with modest instability are supporting rainfall=20
rates up to 0.5 in/hr within some of the more intense showers.=20
These showers are expected to reach eastern West Virginia later=20
this evening, around 03-04Z. While the consensus of the hi-res=20
guidance indicates most areas will receive under 0.5 inch, 3-hr=20
FFGs are as low as 0.25 inch -- indicating even a brief period of=20
heavy rainfall may exacerbate existing flooding issues over the=20
area.=20

Pereira

...Previous Discussion...
Strong N-S quasi-zonal mid and upper level flow will be perturbed=20
a bit during Day 1 (12Z Sat-12Z Sun) as a 150+ kt upper level jet=20
streak traverses the Upper Midwest and Ohio Valley, while a flat=20
500 mb vort lobe pushes across the Lower Great Lakes. Broad-scale=20
exit region forcing associated with the upper jet axis will surge=20 southwesterly low-level inflow ahead of the surface frontal wave,=20
with 850 mb moisture flux anomalies peaking between 4-5 standard=20
deviations above normal later this afternoon into Sat night, while=20
TPW values peak around 1". Robust synoptic-scale support and low-=20
level moisture transport will be offset somewhat by the weak=20
elevated instability, with MUCAPEs generally less than 500 J/Kg.=20 Nevertheless, even though not advertised on the latest (00Z Sat)=20
HREF, the aforementioned dynamic and thermodynamic ingredients will
be sufficient for spotty hourly rain rates of 0.5"+ and 3-hourly=20
rates of 1.0"+, with localized event totals between 1.5-2.0"+.

Current 3-hr flash flood guidance values remain quite low (1" or
less) across the outlook area, which includes much of WV. Despite
the lack of instability, the low FFG values could be exceeded over
isolated areas with 2 consecutive hours of 0.5"+/hr rainfall rates.
Since the soils in these areas are saturated, and the terrain is
rugged, we have maintained the Marginal Risk area for much of WV
(outside of its northern or eastern Panhandles).

Hurley/Roth


Day 2
Valid 12Z Sun Feb 09 2025 - 12Z Mon Feb 10 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Pereira


Day 3
Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Pereira


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_GipmyKKkcctlkl3Bq266nAQpCvgKz1z571JOXrpFZA6= XQWiqjm38nYL_dLvhOQrRmSdKBj8aVhke9yImNu9ENeXvgw$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_GipmyKKkcctlkl3Bq266nAQpCvgKz1z571JOXrpFZA6= XQWiqjm38nYL_dLvhOQrRmSdKBj8aVhke9yImNu9ezXCBXE$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_GipmyKKkcctlkl3Bq266nAQpCvgKz1z571JOXrpFZA6= XQWiqjm38nYL_dLvhOQrRmSdKBj8aVhke9yImNu9j5ZDTqI$=20

=3D =3D =3D
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FOUS30 KWBC 102021
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
321 PM EST Mon Feb 10 2025

Day 1
Valid 16Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

...Arklatex/Lower MS Valley into portions of TN/KY...
Strengthening warm air advection/isentropic ascent associated with
gradually backing mid-level flow and an increasing southwest low-
level jet (reaching 30 to 40+ kts) will facilitate the development
and expansion of moderate to locally heavy shower activity tonight
through Tuesday morning along an axis from northeast TX/southeast
OK northeastward through central and northern AR and into areas of central/western TN and southern KY. Some return of weak elevated
instability will support some localized convection that may yield
some hourly rainfall totals of a 0.25" to 0.50" based off the 12Z
HREF guidance, but generally the rainfall totals tonight going
through 12Z/Tuesday should be in the 1 to 2 inch range. Trends will
continue to be monitored, but these modest rainfall rates/totals
at least through early Tuesday are not likely to result in any FFG
exceedance concerns. Any runoff problems are expected to be
isolated at best.

Orrison

Day 2
Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE
VALLEY...

20z Update: Main adjustment was to expand the Slight risk to the=20
southwest into more of eastern TX. We often see convection get=20
organized further southwest than expected in events like this, and=20
there is growing QPF signal in the 12z ECMWF, UKMET and Gem Reg=20
over this area. Will also note that the CSU GEFS based machine=20
learning guidance also indicates higher probabilities of excessive=20
rainfall further to the southwest into more of eastern TX and=20
southwestern LA. The northeastern extent of the Slight risk was=20
trimmed back a bit over eastern TN and northern GA. Instability=20
will initially be lacking here which should delay the flash flood=20 risk...expect the flash flood risk to pick up more over this area=20
as we head into day 3.

Chenard

...Previous Discussion...

...ArkLaTex-ArkLaMis into the Mid-South and Tennessee Valley...
Increasing coverage of showers and thunderstorms along and ahead of
a well defined cold front trailing a developing area of low
pressure taking shape over the Tennessee Valley will lead to an
increasing threat of excessive rainfall Wednesday into early
Thursday from easter Texas and parts of Arkansas and Louisiana
into the west aspect of the Appalachians of Tennessee and southeast
Kentucky. At the synoptic scale, a broad trough over the western
U.S. will amplify, thereby enhancing the deep-layer ascent and
southwesterly flow/moisture transport over this part of the country
due to a increasing low level flow. 850-700 mb moisture flux
anomalies still look to increase to 2-3 standard deviations above
normal Tuesday/Tuesday night while Precipitable Water values climb
to 1.5-1.75" (around +2 standard deviation above normal). The
strengthening dynamical and thermodynamical support will make for
efficient rainfall rates despite the lack of deep- layer
instability and the exit region of a 125 to 150 kt upper level jet
should aid deep layer vertical ascent. Much of the guidance
generally depicts a widespread swath of 1.5-3" of rain within the
outlook areas, with the most aggressive model being the ECMWF with
maximum values exceeding 4 inches. Storm motions nearly parallel
to the WSW-ENE oriented surface boundary will boost the potential
for training despite meager deep- layer elevated instability
(MUCAPEs generally 250-500 J/Kg). With 2.00"+/3hr rainfall rates
still being anticipated where the cells do train, again most
likely within the Slight Risk area, which could lead to localized-
scattered instances of flash flooding.

Bann

Day 3
Valid 12Z Wed Feb 12 2025 - 12Z Thu Feb 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
TENNESSEE VALLEY INTO THE MID-SOUTH...

20z Update: The prolonged heavy rainfall event will continue=20
Wednesday into Wednesday night over the Southeast. The extended=20
duration of this event will lead to storm total rainfall into the=20
3-5" range, with locally higher totals possible. As stronger=20
forcing ejects eastward on Wednesday, an increase in the low level
jet should aid in both increasing moisture convergence and=20
advecting instability northward. Thus higher rainfall rates are=20 possible...and these higher rates moving over what should be=20
saturating ground conditions could result in an increased flash=20
flood risk by later in the period. The best chance of this=20
occurring is currently over portions of northern AL/GA into far=20
southeastern TN and the far western Carolinas. Do consider this a=20
higher end Slight risk over these areas. Can not rule out an=20
eventual MDT risk upgrade pending model trends over the coming days
and how effective the extended duration of rain is at saturating=20
what will initially be dry soil and streamflow conditions.

Chenard

...Previous Discussion...=20

...Tennessee Valley into the Mid-South...
The threat of excessive rainfall will continue on Wednesday and
early Thursday ahead of the same system which brought the
excessive rainfall potential on Tuesday into early Wednesday as a
cold front makes its way eastward. Broad scale ascent will continue
to aided by the southern entrance region of a 135 to 155 kt upper
level jet...while moisture convergence is maximized along a well
defined surface cold front which intercepts a plume of moisture
being pulled northward by a 40 to 50 knot low level jet. There is
still spread in the guidance about placement of where the heaviest
rainfall will occur but amounts generally in the 1 to 3 inch
range...with locally higher amount where any enhanced rainfall
rates set up due to banding/training. Given antecedent
conditions...feel that a Slight risk should suffice.


...California Coast...
The plume of moisture from the Pacific Ocean towards the end of Day
2 will start to bring rain to the coastal areas during the Day 3 period...beginning in northern and central portions of California
on Wednesday that propagates southward during Wednesday night and
Thursday. Present indications are that the heaviest amounts remain
off shore...but a general uptick in amounts was noted over the past
24 hours in this area.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!883TzQjPq24cdhpHmAXDtkOBuBvwzPdJWvqUPkUjDwuX= ixgBYFwIcAu2gUQX0HrInwC08u8ejVUY-P2-I_keg5cZIjo$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!883TzQjPq24cdhpHmAXDtkOBuBvwzPdJWvqUPkUjDwuX= ixgBYFwIcAu2gUQX0HrInwC08u8ejVUY-P2-I_keOZe1_mE$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!883TzQjPq24cdhpHmAXDtkOBuBvwzPdJWvqUPkUjDwuX= ixgBYFwIcAu2gUQX0HrInwC08u8ejVUY-P2-I_kefcLB_-U$=20

=3D =3D =3D
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FOUS30 KWBC 121905
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
205 PM EST Wed Feb 12 2025

Day 1
Valid 16Z Wed Feb 12 2025 - 12Z Thu Feb 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS MUCH OF THE
DEEP SOUTH AND COASTAL AREAS OF CALIFORNIA...

...Southeast...

Large Marginal and Slight Risk areas extend from
Louisiana to the central Appalachians and portions of Virginia. The
Marginal and Slight Risk areas cover multiple regimes for
excessive rainfall potential:

1) Long-duration, moderate to heavy rainfall along an axis
extending from east Texas east-northeastward into northern Georgia
and the southern Appalachians. Much of this axis has experienced
appreciable antecedent rainfall amounts (in the 2-3 inch range on
February 11) and models are consistent in depicting at least one
more round of heavy rain across that same axis as a thunderstorm
complex organizes and moves east- northeastward from in Texas today.
Another 1-3 inches of is expected (heaviest from western in to
central Mississippi). Given the wet soils from prior rainfall,
several instances of flash flooding are expected from central
Louisiana through the southern Appalachians and northern Georgia.

2) Somewhat lighter rainfall should occur across portions of
Virginia and West Virginia through the day. Not only are soils
water-logged and streamflows above average across these areas, but
recent snow/ice could melt under persistent warm advection and
temperatures slowly rising above freezing through the forecast
period. Light to moderate rainfall could enhance excessive
runoff/ponding especially in sensitive areas and low spots.

3) CAMs are in very loose agreement in depiction of east-west
oriented outflow boundary left behind by convective complex(es)
across portions of southern MS/AL through early afternoon. Strong south-southwesterly 850mb flow and abundant moisture should result
in reignition of deep convection focused along boundaries for much
of the afternoon and early evening. The orientation of these
boundaries should focus convective development and may allow for
training and intense rainfall rates at times. This is supported in
particular by the 12Z HRRR, which depicts 4-8 inch rain amounts
across central Alabama and north-central Georgia through 12Z
Thursday. There remains some uncertainty in the exact placement of
the heaviest axis, but initial 12Z guidance is clustering on this
area for the potential of higher-end flash flooding (locally
significant), particularly for the urbanized areas like Birmingham
and Atlanta metros.


...California...
The initial wave of the AR is set to arrive after 00Z this evening,
with the best IVT values reaching the coast around 06Z. As a result
of this slightly faster timing and consensus of the models for rain
rates to approach or exceed 0.5"/hr after 09Z, a Slight Risk was
introduced. Through 12Z Thursday, rainfall totals of 1-1.5" will be
possible along the favored coastal terrain areas with some isolated
amounts nearing 2". Given this, isolated to scattered instances of
flooding will be possible.

Cook/Taylor

Day 2
Valid 12Z Thu Feb 13 2025 - 12Z Fri Feb 14 2025

..THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL PARTS OF THE
SOUTHERN CALIFORNIA COAST...

...California...
The peak of the atmospheric river is expected during this period
with the initial focus on coastal central California at the start
of the period, then the best IVT shifts southward through the
period, reaching southern California by the end of the period
Thursday night. IVT values from the GFS peak at around 600-700
kg/m/s initially along the central coast then settle around 400-500
kg/m/s as the AR reaches SoCal. The greatest QPF amounts will be
confined to the coastal terrain areas as well as for the Sierra.
Total amounts for the 24-hour period look to be between 1-3" with
the favored terrain areas and peaks topping out between 4- 6"+.

The primary concern is the potential for damaging and potentially life-threatening burn scar flash flooding and debris flows,
particularly for southern California where the Moderate Risk (Level
3/4) is in place. Even outside the burn scar regions, the intense
rain rates and rainfall totals over the highly urbanized area could
bring scattered to numerous instances of flash flooding. Elsewhere,
a broad Slight Risk (Level 2/4) exists for much of the coastal
ranges as well as the Central Valley and lower elevations of the
Sierra Nevada.


...Florida Panhandle and Southern Georgia...
Lingering heavy rainfall will continue Thursday across portions of
the Florida Panhandle and southern Georgia, ahead of the approaching
cold front. Rainfall amounts look to be generally in the 1-3"
range, with some potential for localized rain rates sufficiently
high enough to cause some urban/localized flooding concerns.

Hurley/Taylor


Day 3
Valid 12Z Fri Feb 14 2025 - 12Z Sat Feb 15 2025

...Southern California...
IVT plume weakens while pushing southward across SoCal to begin
the Day 3 Period. While the bulk of the event (Slight-Moderate
excessive rainfall risk) is expected on Day 2 or through Thursday
night, will maintain a Marginal Risk into the early part of Day 3
(Friday morning), especially if the southward AR progression slows
down a bit.

...Mid South...
Amplifying longwave trough across the Southwest-4 Corners Region
Fri-Fri night will lead to backing mid/upper layer flow and
deepening WAA/moistening downstream within a maturing Warm Conveyor
Belt (WCB). Thermodynamic profiles will respond appreciably as a
result, especially late in the period (Fri night) as the low- level
flow backs SSW and increases (to 50+ kts at 850 mb). This leads to
robust low-level moisture transport late Friday night into early
Saturday morning, with 850-700 mb moisture flux anomalies ramping
up to 4-5 standard deviations above normal per the ensembles. There
will also be a corresponding uptick in elevated instability as
well, to the tune of 500-1000 J/Kg towards 12Z Sat. While the main
event will be on Saturday (see Day 4 ERO), will maintain the
Marginal Risk given the anticipation of the ingredients ramping up
fairly quickly Friday night, which given the probabilistic QPF=20
along with the latest CSU UFVS-verified ERO first-guess fields,=20
could lead to localized runoff issues across portions of the Mid=20
South. by the pre- dawn hours Saturday.

Hurley/Taylor


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-cLyjPzpF2203aJP2eZxCZKF-UGM9bQCyQssyNUt4Ccc= oeOsl7kQoNoAu8J14O9IQ9lCLnIOiTpaJvyPq2F21RGwIqU$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-cLyjPzpF2203aJP2eZxCZKF-UGM9bQCyQssyNUt4Ccc= oeOsl7kQoNoAu8J14O9IQ9lCLnIOiTpaJvyPq2F2nJ8biMo$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-cLyjPzpF2203aJP2eZxCZKF-UGM9bQCyQssyNUt4Ccc= oeOsl7kQoNoAu8J14O9IQ9lCLnIOiTpaJvyPq2F2jpGyat4$=20

=3D =3D =3D
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FOUS30 KWBC 051516
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1016 AM EST Wed Feb 5 2025

Day 1
Valid 16Z Wed Feb 05 2025 - 12Z Thu Feb 06 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OHIO VALLEY...

...16z Update...

No change to prior reasoning and outlook, other than a minor
adjustment northward to account for the 12z HRRR indicating a
1.5-2.0" stripe of QPF from southwest OH into northern WV and far
southwest PA. Most CAMs are lighter overall with QPF, but a brief
period of embedded training convection is possible, mainly late in
the period (after 06z).=20

Churchill


...Previous Discussion...

No significant changes were made to the Marginal Risk area across
the Ohio Valley. Warm advection showers are expected to break out
over Kentucky, that with the infusion of upper level support and
increasing instability, will allow embedded convection to develop
this afternoon and evening. As the moisture plume turns the front
into a warm front over the Tennessee Valley this evening, expect
the addition of upslope into West Virginia to resulting locally=20
heavier rainfall in the favored areas. Any thunderstorms will be=20
capable of rainfall rates to 1.5 inches per hour. Soils in this=20
area remain nearly saturated and rivers are running high from the=20
rainfall event a few days ago. Thus, the additional rainfall=20
forecast today and tonight, even though amounts will likely be=20
lesser, may still cause isolated flash flooding.

Wegman


Day 2
Valid 12Z Thu Feb 06 2025 - 12Z Fri Feb 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE OHIO VALLEY AND CALIFORNIA...

...OH Valley...
Another round of locally heavy rain is expected Thursday across
portions of KY, TN, WV and far western VA along and ahead of an
approaching cold front. Showers and embedded thunderstorms will
likely be ongoing at 12z and may periodically continue through the
day/evening near the only slowly southward shifting front. While
nothing significant, CAPE upwards of 500-1000 j/kg still seems
likely along this corridor, which should be enough to support
locally heavy rainfall rates. While soil conditions and
streamflows are returning closer to average after the flooding
several days ago, some of this region is still likely more
sensitive than normal to additional heavy rainfall. The latest WPC
QPF is generally 0.75"-1", with two day totals locally exceeding
1.5". Given the instability forecast, it seems reasonable that we
will see isolated totals over 2". While the 00z GEM Reg and FV3LAM
are probably too high with totals, they both do suggest that if
convective coverage can increase enough then some 2-3" amounts can
not be ruled out. Overall expect this rainfall to pose a localized
flood risk.

...California...
After a one day break another system is forecast to move into CA
on Thursday. This is expected to be a pretty dynamic system, with a
strong mid level shortwave and upper level jet. These dynamics
should support a short duration period of enhanced rainfall
rates...although the quick forward motion of the system will limit
overall rainfall magnitudes. Recent model runs are showing some
uptick in rainfall amounts with this system over northern CA, but
still generally looking at totals in the 1-2" range. Given the
saturated conditions and brief potential for higher rates between
00z and 06z, this may be approaching Slight risk levels. Although
will hold off for now as the short duration of these higher rates
may limit the magnitude/coverage of impacts just enough to keep the
risk at Marginal.

The Marginal risk extends southward into Santa Barbara, Ventura and
Los Angeles counties as well. Less rainfall forecast here, but
there is an uptick in IVT into the terrain Thursday night, and PWs
do increase towards and just over 1". Larger scale forcing
generally shears off to the north, but the combination of
increasing PWs, IVT and upslope flow should be enough to result in
a period of moderate to locally heavy rain. We are beginning to
see a slow uptick in rainfall amounts in the models, and so
localized flood impacts are certainly a possibility. Although
given the overall weakening of the system and very little to no
instability, rainfall rates will probably only be high enough to
result in a minor flood risk over just the most sensitive urban
areas or recent burn scar locations.

Chenard

Day 3
Valid 12Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4Qftoz4WnzM0bLaMMXMT4IVYym0EOVDC5JZJGcKCyN96= GR8DgvVvXP-L3PwuA5i6JFJxW8QOxEsn8xGCLRCH9p2-Z2g$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4Qftoz4WnzM0bLaMMXMT4IVYym0EOVDC5JZJGcKCyN96= GR8DgvVvXP-L3PwuA5i6JFJxW8QOxEsn8xGCLRCHWaUWz9o$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4Qftoz4WnzM0bLaMMXMT4IVYym0EOVDC5JZJGcKCyN96= GR8DgvVvXP-L3PwuA5i6JFJxW8QOxEsn8xGCLRCH9rrO_3Q$=20

=3D =3D =3D
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FOUS30 KWBC 061915
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
215 PM EST Thu Feb 6 2025

Day 1
Valid 16Z Thu Feb 06 2025 - 12Z Fri Feb 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF CALIFORNIA AND THE OHIO VALLEY...

...California...

16z update...No changes were made to the Marginal Risk as 12z Hi-
Res and HREF guidance remains on track for heavy rainfall risk. For
a more detailed discussion please refer to Mesoscale Precipitation
Discussion (MPD) 23 that is valid until 03z this evening.

Gallina

---Prior Discussion---
After a one day break another system is
forecast to move into CA today and Thursday night. Not an AR but
rather a compact, dynamic system with a vigorous mid level
shortwave and strong left exit region upper level jet forcing.
These dynamics should support a short duration period of enhanced
rainfall rates, although the quick forward motion of the system
will limit overall rainfall magnitudes. Given the low-level
ageostrophic response ahead of the upper level jet streak, the
latest (00Z) GEFS output shows a quick uptick in southwesterly
850-700 mb moisture transport, peaking between 3-4 standard
deviations above normal across the central 2/3 of CA Thursday
afternoon and evening. Recent model runs continue to show 1-2+
inches falling mostly within 12 hours, with localized amounts of
3+ inches over the coastal ranges and Sierra foothills per the
latest high-res guidance. Given the saturated conditions and brief
potential for higher rates (0.35+ in/hr) beginning around 21Z
along the coast and by 00Z farther inland, this may result in
localized runoff issues, especially over burn scars across Santa
Barbara, Ventura, and Los Angeles counties.

Hurley

...TN-OH Valleys into the Western Appalachians...

16z update...Ongoing convection is starting to sag southward across
southern KY into far southern WV and far western VA. This activity
is expected to continue until about 18-19z as forcing slides past
well to the northwest and activity becomes further displaced from
pool of remaining unstable (750-1000 J/kg of SBCAPE) along the
western and central KY/TN boarder. As such, the Marginal Risk was
trimmed across much of northern KY and WV; though a second round of
scattered thunderstorms is expected this evening just north/along
the KY/TN border and south across Middle and eastern TN this
evening. Similar 1.5"+/hr rates and occasional training/repeat
environment crossing lower FFG and fairly saturated upper soil
conditions mainly across the Cumberland Plateau into the
Appalachians warrants maintaining the Marginal Risk here, as well.

Gallina

---Prior Discussion---
Another round of locally heavy rain is expected Thursday across
portions of KY, TN, WV and far western VA- NC along and ahead of an
approaching cold front. Showers and embedded thunderstorms will be
ongoing to start the period (12Z Thu) and may periodically
continue through the day/evening near the only slowly southward
shifting front. While nothing significant, CAPE upwards of 500-1000
J/Kg still seems likely along this corridor, which should be
enough to support locally heavy rainfall rates. While soil
conditions and streamflows are returning closer to average after
the flooding several days ago, some of this region is still likely
more sensitive than normal to additional heavy rainfall. The latest
WPC areal-average QPF peaks between 0.75"-1.25", though per the
CAMs, localized totals between 2-3"+ are expected, which makes
sense given the instability forecast. Overall expect this rainfall
to pose a localized flood risk.

Hurley


Day 2
Valid 12Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Pereira


Day 3
Valid 12Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Pereira


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_pjujNhfpXVsZtED5ErQzsOyY0H_yA0NqnLi3sz9kCaR= reRlx1a-DTO81Yepup8MN0hxOuPBwtEz4gyoPGCCZYQZtV4$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_pjujNhfpXVsZtED5ErQzsOyY0H_yA0NqnLi3sz9kCaR= reRlx1a-DTO81Yepup8MN0hxOuPBwtEz4gyoPGCC5XW4qAY$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_pjujNhfpXVsZtED5ErQzsOyY0H_yA0NqnLi3sz9kCaR= reRlx1a-DTO81Yepup8MN0hxOuPBwtEz4gyoPGCCXOsHTBs$=20

=3D =3D =3D
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FOUS30 KWBC 072259
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
559 PM EST Fri Feb 7 2025

Day 1
Valid 01Z Sat Feb 08 2025 - 12Z Sat Feb 08 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Roth/Churchill/Hurley


Day 2
Valid 12Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025

West Virginia...
An approaching frontal wave is expected to bring precipitable water
values up above an inch into WV. While 1000-500 hPa thickness
values are higher when compared to Thursday's rainfall farther
south, implying slightly less atmospheric saturation, the
combination of 50+ kts of 850 hPa inflow into WV along with ~100
J/kg of CAPE and the forecast precipitable water values should be
sufficient for hourly rain totals of 0.5"+, even though this is not
advertised in the 12z HREF. The three hour flash flood guidance
values are so low (around 1") that those values could be exceeded
with two hours of such rains. Since soils there are saturated, and
the terrain is rugged, opted to add a Marginal Risk area for much
of WV (outside of its northern or eastern Panhandles) in
coordination with the Charleston WV forecast office. This also
helps support their and Blacksburg VA's new flood watch.

Roth



Day 3
Valid 12Z Sun Feb 09 2025 - 12Z Mon Feb 10 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Roth/Hurley


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-ErhlI-SyWemW0Vdmpi7xFeRC6hKBYpv86LcJF4rz_-h= 7CNQEr8LwvQ2hGPtk3I0XiiDEWq9HAOcA9F1oT0NNKtWXy0$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-ErhlI-SyWemW0Vdmpi7xFeRC6hKBYpv86LcJF4rz_-h= 7CNQEr8LwvQ2hGPtk3I0XiiDEWq9HAOcA9F1oT0NNySuAms$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-ErhlI-SyWemW0Vdmpi7xFeRC6hKBYpv86LcJF4rz_-h= 7CNQEr8LwvQ2hGPtk3I0XiiDEWq9HAOcA9F1oT0NJVt0LR4$=20

=3D =3D =3D
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FOUS30 KWBC 100829
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
329 AM EST Mon Feb 10 2025

Day 1
Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Beginning Monday afternoon, an increase of convergence on the nose
of 850mb flow extending from Texas into Tennessee will support an
increase in light to moderate rain and a few rumbles of thunder
from eastern Oklahoma through Kentucky/Tennessee. Rain rates are
expected to be modest (around 0.25-0.5 inch/3-hour period),
although some of this rainfall will eventually reach areas of
southeastern Kentucky where soils are moist and sensitive from
antecedent rainfall. The relatively short duration of light to
moderate rainfall in this area precludes an introduction of
Marginal/5% risk probabilities, although one may be needed in later
outlook updates if a longer duration of rainfall (greater than 3-6
hours) becomes apparent across southeastern Kentucky.

Cook

Day 2
Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF=20
THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE=20
VALLEY...

...ArkLaTex-ArkLaMis into the Mid-South and Tennessee Valley...
Increasing coverage of showers and thunderstorms along and ahead of
a well defined cold front trailing a developing area of low
pressure taking shape over the Tennessee Valley will lead to an
increasing threat of excessive rainfall Wednesday into early
Thursday from easter Texas and parts of Arkansas and Louisiana
into the west aspect of the Appalachians of Tennessee and southeast
Kentucky. At the synoptic scale, a broad trough over the western=20
U.S. will amplify, thereby enhancing the deep-layer ascent and=20
southwesterly flow/moisture transport over this part of the country
due to a increasing low level flow. 850-700 mb moisture flux=20
anomalies still look to increase to 2-3 standard deviations above=20
normal Tuesday/Tuesday night while Precipitable Water values climb
to 1.5-1.75" (around +2 standard deviation above normal). The=20
strengthening dynamical and thermodynamical support will make for=20
efficient rainfall rates despite the lack of deep- layer=20
instability and the exit region of a 125 to 150 kt upper level jet
should aid deep layer vertical ascent. Much of the guidance
generally depicts a widespread swath of 1.5-3" of rain within the=20
outlook areas, with the most aggressive model being the ECMWF with
maximum values exceeding 4 inches. Storm motions nearly parallel=20
to the WSW-ENE oriented surface boundary will boost the potential=20
for training despite meager deep- layer elevated instability=20
(MUCAPEs generally 250-500 J/Kg). With 2.00"+/3hr rainfall rates=20
still being anticipated where the cells do train, again most=20
likely within the Slight Risk area, which could lead to localized-=20
scattered instances of flash flooding.

Bann

Day 3
Valid 12Z Wed Feb 12 2025 - 12Z Thu Feb 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
TENNESSEE VALLEY INTO THE MID-SOUTH,,,

...Tennessee Valley into the Mid-South...
The threat of excessive rainfall will continue on Wednesday and
early Thursday ahead of the same system which brought the=20
excessive rainfall potential on Tuesday into early Wednesday as a=20
cold front makes its way eastward. Broad scale ascent will continue
to aided by the southern entrance region of a 135 to 155 kt upper=20
level jet...while moisture convergence is maximized along a well=20
defined surface cold front which intercepts a plume of moisture=20
being pulled northward by a 40 to 50 knot low level jet. There is=20
still spread in the guidance about placement of where the heaviest=20
rainfall will occur but amounts generally in the 1 to 3 inch=20
range...with locally higher amount where any enhanced rainfall=20
rates set up due to banding/training. Given antecedent=20
conditions...feel that a Slight risk should suffice.


...California Coast...
The plume of moisture from the Pacific Ocean towards the end of Day
2 will start to bring rain to the coastal areas during the Day 3 period...beginning in northern and central portions of California
on Wednesday that propagates southward during Wednesday night and
Thursday. Present indications are that the heaviest amounts remain
off shore...but a general uptick in amounts was noted over the past
24 hours in this area.=20=20

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4gB-baGvGTNDozaw_1SUVJ22W19fixU0bUhFu0pDrDsH= Cc6AUbTQn-OzsqKOFsSmQMUcZcNmEPsi7trQD4M1gXcK8zY$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4gB-baGvGTNDozaw_1SUVJ22W19fixU0bUhFu0pDrDsH= Cc6AUbTQn-OzsqKOFsSmQMUcZcNmEPsi7trQD4M1HC2tj10$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4gB-baGvGTNDozaw_1SUVJ22W19fixU0bUhFu0pDrDsH= Cc6AUbTQn-OzsqKOFsSmQMUcZcNmEPsi7trQD4M1eoVTejY$=20

=3D =3D =3D
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FOUS30 KWBC 101550
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1050 AM EST Mon Feb 10 2025

Day 1
Valid 16Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

...Arklatex/Lower MS Valley into portions of TN/KY...
Strengthening warm air advection/isentropic ascent associated with
gradually backing mid-level flow and an increasing southwest low-=20
level jet (reaching 30 to 40+ kts) will facilitate the development=20
and expansion of moderate to locally heavy shower activity tonight=20
through Tuesday morning along an axis from northeast TX/southeast=20
OK northeastward through central and northern AR and into areas of=20 central/western TN and southern KY. Some return of weak elevated=20
instability will support some localized convection that may yield=20
some hourly rainfall totals of a 0.25" to 0.50" based off the 12Z=20
HREF guidance, but generally the rainfall totals tonight going=20
through 12Z/Tuesday should be in the 1 to 2 inch range. Trends will
continue to be monitored, but these modest rainfall rates/totals=20
at least through early Tuesday are not likely to result in any FFG=20 exceedance concerns. Any runoff problems are expected to be=20
isolated at best.

Orrison

Day 2
Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE
VALLEY...

...ArkLaTex-ArkLaMis into the Mid-South and Tennessee Valley...
Increasing coverage of showers and thunderstorms along and ahead of
a well defined cold front trailing a developing area of low
pressure taking shape over the Tennessee Valley will lead to an
increasing threat of excessive rainfall Wednesday into early
Thursday from easter Texas and parts of Arkansas and Louisiana
into the west aspect of the Appalachians of Tennessee and southeast
Kentucky. At the synoptic scale, a broad trough over the western
U.S. will amplify, thereby enhancing the deep-layer ascent and
southwesterly flow/moisture transport over this part of the country
due to a increasing low level flow. 850-700 mb moisture flux
anomalies still look to increase to 2-3 standard deviations above
normal Tuesday/Tuesday night while Precipitable Water values climb
to 1.5-1.75" (around +2 standard deviation above normal). The
strengthening dynamical and thermodynamical support will make for
efficient rainfall rates despite the lack of deep- layer
instability and the exit region of a 125 to 150 kt upper level jet
should aid deep layer vertical ascent. Much of the guidance
generally depicts a widespread swath of 1.5-3" of rain within the
outlook areas, with the most aggressive model being the ECMWF with
maximum values exceeding 4 inches. Storm motions nearly parallel
to the WSW-ENE oriented surface boundary will boost the potential
for training despite meager deep- layer elevated instability
(MUCAPEs generally 250-500 J/Kg). With 2.00"+/3hr rainfall rates
still being anticipated where the cells do train, again most
likely within the Slight Risk area, which could lead to localized-
scattered instances of flash flooding.

Bann

Day 3
Valid 12Z Wed Feb 12 2025 - 12Z Thu Feb 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
TENNESSEE VALLEY INTO THE MID-SOUTH,,,

...Tennessee Valley into the Mid-South...
The threat of excessive rainfall will continue on Wednesday and
early Thursday ahead of the same system which brought the
excessive rainfall potential on Tuesday into early Wednesday as a
cold front makes its way eastward. Broad scale ascent will continue
to aided by the southern entrance region of a 135 to 155 kt upper
level jet...while moisture convergence is maximized along a well
defined surface cold front which intercepts a plume of moisture
being pulled northward by a 40 to 50 knot low level jet. There is
still spread in the guidance about placement of where the heaviest
rainfall will occur but amounts generally in the 1 to 3 inch
range...with locally higher amount where any enhanced rainfall
rates set up due to banding/training. Given antecedent
conditions...feel that a Slight risk should suffice.


...California Coast...
The plume of moisture from the Pacific Ocean towards the end of Day
2 will start to bring rain to the coastal areas during the Day 3 period...beginning in northern and central portions of California
on Wednesday that propagates southward during Wednesday night and
Thursday. Present indications are that the heaviest amounts remain
off shore...but a general uptick in amounts was noted over the past
24 hours in this area.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!50c-9U44_ySvVCScOKa1kadpGdmYjG17ZIAFSLym6381= JL8F7qAFokxFCTxDoYfgDO9ClOnxC0O9yXnjYdImd7XVgwk$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!50c-9U44_ySvVCScOKa1kadpGdmYjG17ZIAFSLym6381= JL8F7qAFokxFCTxDoYfgDO9ClOnxC0O9yXnjYdImiQSoPGQ$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!50c-9U44_ySvVCScOKa1kadpGdmYjG17ZIAFSLym6381= JL8F7qAFokxFCTxDoYfgDO9ClOnxC0O9yXnjYdImc3ElzWc$=20

=3D =3D =3D
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FOUS30 KWBC 121534
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1034 AM EST Wed Feb 12 2025

Day 1
Valid 16Z Wed Feb 12 2025 - 12Z Thu Feb 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS MUCH OF THE
DEEP SOUTH AND COASTAL AREAS OF CALIFORNIA...

...Southeast...

Large Marginal and Slight Risk areas extend from=20
Louisiana to the central Appalachians and portions of Virginia. The
Marginal and Slight Risk areas cover multiple regimes for=20
excessive rainfall potential:

1) Long-duration, moderate to heavy rainfall along an axis
extending from east Texas east-northeastward into northern Georgia
and the southern Appalachians. Much of this axis has experienced=20
appreciable antecedent rainfall amounts (in the 2-3 inch range on=20
February 11) and models are consistent in depicting at least one=20
more round of heavy rain across that same axis as a thunderstorm=20
complex organizes and moves east- northeastward from in Texas today.
Another 1-3 inches of is expected (heaviest from western in to=20
central Mississippi). Given the wet soils from prior rainfall,=20
several instances of flash flooding are expected from central=20
Louisiana through the southern Appalachians and northern Georgia.

2) Somewhat lighter rainfall should occur across portions of
Virginia and West Virginia through the day. Not only are soils
water-logged and streamflows above average across these areas, but
recent snow/ice could melt under persistent warm advection and
temperatures slowly rising above freezing through the forecast
period. Light to moderate rainfall could enhance excessive
runoff/ponding especially in sensitive areas and low spots.

3) CAMs are in very loose agreement in depiction of east-west
oriented outflow boundary left behind by convective complex(es)
across portions of southern MS/AL through early afternoon. Strong south-southwesterly 850mb flow and abundant moisture should result
in reignition of deep convection focused along boundaries for much
of the afternoon and early evening. The orientation of these
boundaries should focus convective development and may allow for
training and intense rainfall rates at times. This is supported in
particular by the 12Z HRRR, which depicts 4-8 inch rain amounts=20
across central Alabama and north-central Georgia through 12Z=20
Thursday. There remains some uncertainty in the exact placement of
the heaviest axis, but initial 12Z guidance is clustering on this
area for the potential of higher-end flash flooding (locally
significant), particularly for the urbanized areas like Birmingham
and Atlanta metros.=20=20


...California...
The initial wave of the AR is set to arrive after 00Z this evening,
with the best IVT values reaching the coast around 06Z. As a result
of this slightly faster timing and consensus of the models for rain
rates to approach or exceed 0.5"/hr after 09Z, a Slight Risk was
introduced. Through 12Z Thursday, rainfall totals of 1-1.5" will be
possible along the favored coastal terrain areas with some isolated
amounts nearing 2". Given this, isolated to scattered instances of
flooding will be possible.=20

Cook/Taylor

Day 2
Valid 12Z Thu Feb 13 2025 - 12Z Fri Feb 14 2025

..THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL PARTS OF THE
SOUTHERN CALIFORNIA COAST...

...California...
The peak of the atmospheric river is expected during this period
with the initial focus on coastal central California at the start
of the period, then the best IVT shifts southward through the
period, reaching southern California by the end of the period
Thursday night. IVT values from the GFS peak at around 600-700
kg/m/s initially along the central coast then settle around 400-500
kg/m/s as the AR reaches SoCal. The greatest QPF amounts will be
confined to the coastal terrain areas as well as for the Sierra.
Total amounts for the 24-hour period look to be between 1-3" with
the favored terrain areas and peaks topping out between 4- 6"+.

The primary concern is the potential for damaging and potentially life-threatening burn scar flash flooding and debris flows,
particularly for southern California where the Moderate Risk (Level
3/4) is in place. Even outside the burn scar regions, the intense
rain rates and rainfall totals over the highly urbanized area could
bring scattered to numerous instances of flash flooding. Elsewhere,
a broad Slight Risk (Level 2/4) exists for much of the coastal
ranges as well as the Central Valley and lower elevations of the
Sierra Nevada.

A Moderate Risk of excessive rainfall continues from yesterday's Day
3 ERO across portions of the Southern California coast, and for the
new Day 2 ERO was expanded slightly on the northwest side to
encompass the Lake Burn Scar (2024), while also eastward to include
the southwest San Bernardino Mountains, including the Line Burn Scar
(also 2024). Again, the primary concern is for damaging flooding and
debris flow from the numerous fresh burn scars in the region given
the 24-hour QPF in the 1.5 to 3.5 inch range (with localized higher
amounts). In addition, the area is highly urbanized and an
environment in which much of the rainfall will turn immediately to
runoff.

Farther inland, given the QPF trends and snow levels, the Slight
Risk was extended into eastern portions of the San Joaquin Valley
and southern Sierra/adjacent foothills. This expansion includes the
Borel burn scar (2024).

...Florida Panhandle and Southern Georgia...
Lingering heavy rainfall will continue Thursday across portions of
the Florida Panhandle and southern Georgia, ahead of the approaching
cold front. Rainfall amounts look to be generally in the 1-3"
range, with some potential for localized rain rates sufficiently
high enough to cause some urban/localized flooding concerns.

Hurley/Taylor


Day 3
Valid 12Z Fri Feb 14 2025 - 12Z Sat Feb 15 2025

...Southern California...
IVT plume weakens while pushing southward across SoCal to begin
the Day 3 Period. While the bulk of the event (Slight-Moderate
excessive rainfall risk) is expected on Day 2 or through Thursday
night, will maintain a Marginal Risk into the early part of Day 3
(Friday morning), especially if the southward AR progression slows
down a bit.

...Mid South...
Amplifying longwave trough across the Southwest-4 Corners Region
Fri-Fri night will lead to backing mid/upper layer flow and
deepening WAA/moistening downstream within a maturing Warm Conveyor
Belt (WCB). Thermodynamic profiles will respond appreciably as a
result, especially late in the period (Fri night) as the low- level
flow backs SSW and increases (to 50+ kts at 850 mb). This leads to
robust low-level moisture transport late Friday night into early
Saturday morning, with 850-700 mb moisture flux anomalies ramping
up to 4-5 standard deviations above normal per the ensembles. There
will also be a corresponding uptick in elevated instability as
well, to the tune of 500-1000 J/Kg towards 12Z Sat. While the main
event will be on Saturday (see Day 4 ERO), will maintain the
Marginal Risk inherited from yesterday's Day 4 ERO given the
anticipation of the ingredients ramping up fairly quickly Friday
night, which given the probabilistic QPF along with the latest CSU UFVS-verified ERO first-guess fields, could lead to localized
runoff issues across portions of the Mid South. by the pre- dawn
hours Saturday.

Hurley


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6VcpUGLaH49YlboB-bK3W-pj3Vh-dK-jRX3EZsw4Jzab= Zljndo-hndTvRxuJxuaxCG9980MM2_MIJ0Eu2eiZmKPsGyM$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6VcpUGLaH49YlboB-bK3W-pj3Vh-dK-jRX3EZsw4Jzab= Zljndo-hndTvRxuJxuaxCG9980MM2_MIJ0Eu2eiZYoP8kTc$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6VcpUGLaH49YlboB-bK3W-pj3Vh-dK-jRX3EZsw4Jzab= Zljndo-hndTvRxuJxuaxCG9980MM2_MIJ0Eu2eiZ4KLbe0k$=20

=3D =3D =3D
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FOUS30 KWBC 140808
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
308 AM EST Fri Feb 14 2025

Day 1
Valid 12Z Fri Feb 14 2025 - 12Z Sat Feb 15 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS=20
OF THE MID-SOUTH...

Models continue to show ingredients coming together late in the
period to support a developing heavy rain that will evolve into a
much larger threat on Day 2. Deepening moisture coincident with a
southwesterly 50 kt low level jet, interacting with mid-level
energy, is expected to support showers and storms developing=20
across the region Saturday morning. There is some signal in the hi-res
models showing storms beginning to train, raising an increasing=20
threat for heavy accumulations near the end of the period. While=20
widespread heavy amounts are not expected prior to 12Z, this=20
continued signal in some of the guidance for training storms with
locally heavy amounts beginning to develop, warranted leaving the=20
Marginal Risk in place across portions of the region. However, the=20
areal extent of the risk was reduced some from the previous,=20
confining the area mostly to where the 00Z HREF showed the highest=20 neighborhood probabilities for accumulations of an inch or more.=20

Pereira

Day 2
Valid 12Z Sat Feb 15 2025 - 12Z Sun Feb 16 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF=20
THE TENNESSEE AND OHIO VALLEYS AND THE CENTRAL APPALACHIANS...

...Ohio and Tennessee Valleys...

Confidence remains high in significant heavy rainfall and flash=20
flood event across the region on Saturday and Saturday Night. Models=20 continue to depict a swath of 3-6 inches of rainfall in the 24-hour=20
period, although there continues to be some variability on the exact=20 placement. Therefore, the maximum risk level was held at a Moderate=20
Risk for this outlook, and the biggest change was to shift the=20
overall footprint slightly further to the northwest (by 25-50 mi)=20
based on trends in the 00 UTC model guidance. The Moderate Risk area=20
was also trimmed a bit in the Central Appalachians where model QPF=20
has been trending lower and the region will be removed from the area=20
of greatest instability (and thus likely to see lower rain rates.)

Based on cluster analysis, a primary source of uncertainty seems to=20
be related to the position of the surface low. This makes sense as a=20
more northward track of the low would allow for a more significant=20
poleward push of the warm front and overall warm sector. Although=20
the 00 UTC NAM, NAM Nest, and GFS have trended the swath of rainfall=20
further northwest, this is far from unanimous. In fact, AI-based=20
versions of the ECMWF and GFS have been fairly consistent in their=20
depiction of the overall scenario and are among the furthest south=20
with the position of the surface low. Therefore, although the=20
overall risk areas were trended slightly to the northwest out of=20
deference to the overall ensemble envelope, the changes were=20
incremental at this point and still include a reasonable chance of=20
some of the southern scenarios unfolding.

An emerging point of consensus among many models, though, appears to=20
be a focus of the heaviest rainfall generally between 85W and 90W=20
longitude, or likely somewhere in W/C KY or NW TN. This is an area=20
that would be favored to receive both the early round of training=20
and backbuilding convection along the developing warm front in the=20
morning and early afternoon, as well as more vigorous convection as=20
the surface low tracks nearby with increasing surface-based=20
instability. This would potentially maximize both the peak intensity=20
of rain rates as well as the overall duration of heavy rain. It also=20
happens to coincide with the most significant above-normal precip=20
departures over the past 30 days, with precip in that period along=20
an axis from DYR-LEX generally 1.5 to 2.0 times the normal amount.=20 Therefore, this is an area that will continue to be monitored for=20
any potential risk upgrades to a High Risk if it becomes apparent=20
that the duration of heavier rain rates will last for at least=20
several hours. More transient bursts of heavy rain would be less=20
likely to lead to severe impacts, and it is the uncertainty of both=20
the placement of the heavy rain and the extent to which it will be=20 concentrated in a sustained period that preclude a risk upgrade at=20
the present moment.

The environment will be quite unusual for mid-February. The=20
combination of MUCAPE of 500-1000 j/kg and PWATs reaching around 1.5=20
inches has only rarely been observed in KY/TN at this time of year,=20
and would be supportive of 1-2 inch per hour rain rates in the most=20 organized and intense convection. A powerful southwesterly LLJ over=20
60 knots, oriented at an acute angle to the developing warm front,=20
will favor backbuilding into the region of stronger instability. And=20
the overall mean flow should favor some periods of training=20
convective clusters or bands near the warm front and surface low=20
track. All of these ingredients are fairly classic for impactful=20
flash flooding cases, and significant impacts are possible in this=20
one as well.

Lamers

Day 3
Valid 12Z Sun Feb 16 2025 - 12Z Mon Feb 17 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN PORTIONS OF THE=20 MID-ATLANTIC...

...Mid-Atlantic...

A Marginal Risk was maintained across portions of the Mid-Atlantic=20
region on Sunday, primarily due to the potential for briefly heavy=20
rain rates with convection along an advancing cold front, and fairly=20
low flash flood guidance values. However, the speed of the cold=20
front should reduce the duration of any heavy rain, and thus any=20
flash flood threat should remain rather isolated.

Lamers


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_KOS5jIHWJ1iDdm1eCLAZLomanfhb6JfeYCm2He0duGH= XbN_ju3Zvlk3kSmr3UFPJEFx__fQPE29ueTZ3hbIfwlHiG0$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_KOS5jIHWJ1iDdm1eCLAZLomanfhb6JfeYCm2He0duGH= XbN_ju3Zvlk3kSmr3UFPJEFx__fQPE29ueTZ3hbIH3UufdQ$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_KOS5jIHWJ1iDdm1eCLAZLomanfhb6JfeYCm2He0duGH= XbN_ju3Zvlk3kSmr3UFPJEFx__fQPE29ueTZ3hbIRPkYSh0$=20

=3D =3D =3D
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FOUS30 KWBC 141542
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1042 AM EST Fri Feb 14 2025

Day 1
Valid 16Z Fri Feb 14 2025 - 12Z Sat Feb 15 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE MID-SOUTH...

16Z Update: No significant changes were made to the risk area, some
broadening to account for some of the model variability and latest
HREF probabilities. Otherwise, the risk area looks good leading
into the more significant heavy rainfall threat for the current Day
2 period.=20

---previous discussion---

Models continue to show ingredients coming together late in the
period to support a developing heavy rain that will evolve into a
much larger threat on Day 2. Deepening moisture coincident with a
southwesterly 50 kt low level jet, interacting with mid-level
energy, is expected to support showers and storms developing
across the region Saturday morning. There is some signal in the hi-res
models showing storms beginning to train, raising an increasing
threat for heavy accumulations near the end of the period. While
widespread heavy amounts are not expected prior to 12Z, this
continued signal in some of the guidance for training storms with
locally heavy amounts beginning to develop, warranted leaving the
Marginal Risk in place across portions of the region. However, the
areal extent of the risk was reduced some from the previous,
confining the area mostly to where the 00Z HREF showed the highest
neighborhood probabilities for accumulations of an inch or more.

Pereira/Taylor

Day 2
Valid 12Z Sat Feb 15 2025 - 12Z Sun Feb 16 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE TENNESSEE AND OHIO VALLEYS AND THE CENTRAL APPALACHIANS...

...Ohio and Tennessee Valleys...

Confidence remains high in significant heavy rainfall and flash
flood event across the region on Saturday and Saturday Night. Models
continue to depict a swath of 3-6 inches of rainfall in the 24-hour
period, although there continues to be some variability on the exact
placement. Therefore, the maximum risk level was held at a Moderate
Risk for this outlook, and the biggest change was to shift the
overall footprint slightly further to the northwest (by 25-50 mi)
based on trends in the 00 UTC model guidance. The Moderate Risk area
was also trimmed a bit in the Central Appalachians where model QPF
has been trending lower and the region will be removed from the area
of greatest instability (and thus likely to see lower rain rates.)

Based on cluster analysis, a primary source of uncertainty seems to
be related to the position of the surface low. This makes sense as a
more northward track of the low would allow for a more significant
poleward push of the warm front and overall warm sector. Although
the 00 UTC NAM, NAM Nest, and GFS have trended the swath of rainfall
further northwest, this is far from unanimous. In fact, AI-based
versions of the ECMWF and GFS have been fairly consistent in their
depiction of the overall scenario and are among the furthest south
with the position of the surface low. Therefore, although the
overall risk areas were trended slightly to the northwest out of
deference to the overall ensemble envelope, the changes were
incremental at this point and still include a reasonable chance of
some of the southern scenarios unfolding.

An emerging point of consensus among many models, though, appears to
be a focus of the heaviest rainfall generally between 85W and 90W
longitude, or likely somewhere in W/C KY or NW TN. This is an area
that would be favored to receive both the early round of training
and backbuilding convection along the developing warm front in the
morning and early afternoon, as well as more vigorous convection as
the surface low tracks nearby with increasing surface-based
instability. This would potentially maximize both the peak intensity
of rain rates as well as the overall duration of heavy rain. It also
happens to coincide with the most significant above-normal precip
departures over the past 30 days, with precip in that period along
an axis from DYR-LEX generally 1.5 to 2.0 times the normal amount.
Therefore, this is an area that will continue to be monitored for
any potential risk upgrades to a High Risk if it becomes apparent
that the duration of heavier rain rates will last for at least
several hours. More transient bursts of heavy rain would be less
likely to lead to severe impacts, and it is the uncertainty of both
the placement of the heavy rain and the extent to which it will be
concentrated in a sustained period that preclude a risk upgrade at
the present moment.

The environment will be quite unusual for mid-February. The
combination of MUCAPE of 500-1000 j/kg and PWATs reaching around 1.5
inches has only rarely been observed in KY/TN at this time of year,
and would be supportive of 1-2 inch per hour rain rates in the most
organized and intense convection. A powerful southwesterly LLJ over
60 knots, oriented at an acute angle to the developing warm front,
will favor backbuilding into the region of stronger instability. And
the overall mean flow should favor some periods of training
convective clusters or bands near the warm front and surface low
track. All of these ingredients are fairly classic for impactful
flash flooding cases, and significant impacts are possible in this
one as well.

Lamers

Day 3
Valid 12Z Sun Feb 16 2025 - 12Z Mon Feb 17 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN PORTIONS OF THE MID-ATLANTIC...

...Mid-Atlantic...

A Marginal Risk was maintained across portions of the Mid-Atlantic
region on Sunday, primarily due to the potential for briefly heavy
rain rates with convection along an advancing cold front, and fairly
low flash flood guidance values. However, the speed of the cold
front should reduce the duration of any heavy rain, and thus any
flash flood threat should remain rather isolated.

Lamers


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!42ealGLNG55fwoJU4yFyObN2VyVivy3MVB-ZLFxWZXpG= c9ORUfjU26zD27ldpMnXLqrUGZ20FUQJ14XyMZ2RNXdeV1w$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!42ealGLNG55fwoJU4yFyObN2VyVivy3MVB-ZLFxWZXpG= c9ORUfjU26zD27ldpMnXLqrUGZ20FUQJ14XyMZ2R4LpSyKQ$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!42ealGLNG55fwoJU4yFyObN2VyVivy3MVB-ZLFxWZXpG= c9ORUfjU26zD27ldpMnXLqrUGZ20FUQJ14XyMZ2RlTMmDeI$=20

=3D =3D =3D
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FOUS30 KWBC 041917
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
217 PM EST Tue Feb 4 2025

Day 1
Valid 16Z Tue Feb 04 2025 - 12Z Wed Feb 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL AND NORTHERN CALIFORNIA...

...16z Update...

Slight risk areas remain largely on track for today with little=20
change to the meteorological reasoning from the previous discussion
(see below). Additional adjustments to the Slight and Marginal risk
areas were made based largely on the 12z HREF guidance, which did
result in a tightening/reduction of the overall Slight risk area
(mainly affecting coastal Humboldt county, being reduced to a
Marginal risk). The Slight risk generally encompasses where 1-3"+
additional totals are most likely (as well as the highest risk for
hourly accumulations of 0.5"+), and an additional internal 25%+
(high-end Slight risk probabilities) was introduced for portions of
coastal Monterey county (with the prior 25%+ area for the northern
Sierra foothills maintained for this update) where localized 3-5"
totals (in association with terrain forcing) are most likely.=20
Otherwise, only minor adjustments were made to the surrounding=20
Marginal risk area.


Churchill


...Previous Discussion...

A large and energetic cutoff low that will remain largely stationary
off the coast of Vancouver Island will be the upper level animus for
the active weather ongoing across California today. An atmospheric
river event that has been ongoing for the past several days will
come to an end (or at least take a significant break) during this
period. However, to get to the break, one last potent area of low
pressure moving along the atmospheric river still has to move across California, resulting in another period of heavy rain. The cold air
following behind its cold front will push the AR far enough south
but also far enough away from the forcing to cause it to mostly
dissipate tonight.

The atmospheric river currently is located along the I-80 corridor
from San Francisco through Lake Tahoe. It is expected to shift south
to about a Monterey to Modesto line, leaving the I-80 corridor in
periodic shower activity. It will not move much along the foothills
of the Sierras, where upslope flow will keep the steady rain going
well north of where the core of the atmospheric river is. From the
Bay Area north along the coast, expect a break from the rainfall
through until about 15Z/7am PST. That all changes beyond 15Z, when
the aforementioned low begins to move ashore, resulting in steady
rain for the almost the entire northern half of California. As in
previous days, localized convective enhancement and convergence
bands are expected to develop within the broader rainfall shield.
This will be supported by a strengthening LLJ through the Sacramento
Valley, which will intensify due to the approach of the southerly
flow ahead of the low. Colder and drier air following behind the low
will begin to clear the precipitation out from northwest to
southeast starting around 22Z/2pm PST. Until the back edge clears,
locally heady rain will continue, which will be enhanced by the
passage of the surface cold front itself, bringing a brief period of
heavy rain for most of northern California during the late afternoon
and evening hours, potentially impacting this evening's commute.

After about sunset or so, the entire atmospheric river will weaken,
though the prevailing southwesterly upslope flow may continue much
lighter rain into the Transverse Ranges, the southern Sierras, and
eventually the Los Angeles Metro area. Despite the recent fires in
that area, the rain should be light enough east of Santa Barbara
County that there should not be enough to cause flooding concerns,
so the light rain from the showers should be beneficial, if not
nearly enough to dent the ongoing drought conditions in southern
California.

All of the guidance has shifted significantly northward with the
track of the incoming low for the day today. This resulted in a
northward shift in the ERO risk areas, with the Slight Risk being
expanded well up the coast to Mendocino County and all of the
northern Coast Ranges and trimmed out of the southern Central
Valley. An internal higher-end Slight was added to most of the
foothills of the northern Sierras since this area stands to pick up
an additional 3-5 inches of rain on top of the foot+ they've seen
the past few days.

The ERO trimming was due to rain shadowing from the southern Coast
Ranges. Unlike previous days, the southern Coast Ranges from the
Santa Cruz Mountains south through the western Transverse Ranges
should all get a healthy soaking today from the atmospheric river,
though since those areas have seen significantly less rainfall in
recent days compared to areas further north, have left most of these
areas in the Marginal.

Wegman


Day 2
Valid 12Z Wed Feb 05 2025 - 12Z Thu Feb 06 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OHIO VALLEY...

Strong southwesterly flow will advect abundant moisture northward
into the OH Valley on Wed into Wed night, with PWs forecast to
increase over the 90th percentile for early February. Increasing
WAA, a mid level shortwave moving east within the quick zonal
flow, and upper level divergence in the right entrance region of a
jet to the north and left exit region of a strong jet over the MS
Valley, will broadly support an expansion of showers across the
region. Model guidance continues to indicate upwards of 500-1000
j/kg near and south of a northward moving warm front, thus expect
we will see embedded thunderstorms as well. Given the forcing,
moisture and instability forecast, do anticipate we will see some
locally heavy rainfall rates materialize, especially by Wed evening
into the overnight near the lifting warm front.

Still some uncertainty on the location of this front, although
models are in much better agreement tonight compared to last
night. Precipitation north of the front will likely be either sleet
or freezing rain, and thus the position of this feature will be
important to delineate the northern edge of the flood risk area.
The current consensus for the axis of heaviest rainfall is across
portions of KY, southern IN/OH into much of WV. Some of these areas
may start as sleet/freezing rain, but will transition to locally
heavy rain as the warm front lifts north. Areal averaged rainfall
is currently forecast in the 0.5"-1" range, although given the
forecast instability, locally higher totals ~2" appear possible.
Portions of central/eastern KY into WV have above average soil
saturation and streamflows, and so this area is likely most
susceptible to some flooding impacts if higher rainfall rates do
materialize.

Chenard

2100 UTC Update

Only some minor changes made to the previous marginal risk outlook
from the OH Valley into the Central Appalachians. While there is
still some spread with respect to the qpf details day 2 across
these regions, there is consensus for a tightening of the precip
gradient with lesser amounts on the northern edge. We have
subsequently adjusted the marginal risk approximately 40-50 miles
to the south across southern IN and southern OH. Otherwise, no
changes to the previous thinking with locally heavy rainfall across
areas where soils are saturated or nearly saturated, resulting in
localized runoff issues.

Oravec


Day 3
Valid 12Z Thu Feb 06 2025 - 12Z Fri Feb 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE OHIO VALLEY AND CALIFORNIA...

...OH Valley...
Another round of locally heavy rain is expected Thursday across
portions of KT/TN and WV along and ahead of an approaching cold
front. Locally heavy rainfall should be ongoing at 12z Thursday
across portions of WV, before a relative lull in activity by late
morning into the early afternoon. However by later in the afternoon
into the overnight hours another round of showers and embedded
thunderstorms should develop near the cold front over KY and
spread eastward into WV. Seeing enough instability forecast to
support locally heavy rainfall rates. Some of this corridor already
has above average soil saturation and streamflows, and there is
also some overlap between this day 3 rainfall and the day 2 rains.
Two day rainfall totals of 1-2" are forecast, but given the
instability both days, some areas could locally exceed 3". This
rainfall should be enough to result in at least some flooding
impacts.

...California...
After a one day break another system is forecast to move into CA
on Thursday. This is expected to be a pretty dynamic system, with a
strong mid level shortwave and upper level jet. These dynamics
should support a short duration period of enhanced rainfall
rates...although the quick forward motion of the system will limit
overall rainfall magnitudes. Not seeing much in the way of
instability currently forecast, and IVT and PWs are not overly
anomalous with this system either. These limitations will be
somewhat made up for by the stronger dynamics, however still not
expecting this to be a high end event. Rainfall totals around 1"
are forecast along coastal areas with 1-2" in the foothills of the
Sierra (snow levels will be lower with this system limiting
impacts). Given the saturated conditions over the region, this
quick shot of locally heavy rainfall may still be enough to
generate localized flood impacts, supporting the Marginal risk.

The Marginal risk extends southward into Santa Barbara, Ventura and
Los Angeles counties as well. Less rainfall forecast here, but
there is an uptick in IVT into the terrain, and so would not be
surprised if QPF trends up a bit as the event nears. Still not
expecting significant rainfall, but possibly enough for localized
impacts.

Chenard

2100 UTC Update.

No changes made to the previous marginal risk areas from the
Central Appalachians into the Upper TN Valley. Still some north
south spread in the latest guidance, but consensus for locally
heavy total over saturated soils which may lead to localized runoff
issues.


No changes also made to the marginal risk area across coastal
central CA, inland into the northern Sacramento Valley and upslope
of the Central to Northern Sierra with the last in the current
series of heavy precip events forecast to affect CA.

Oravec



Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!9Ru3u8N6q4gzK-A766p3b7EWawZQ8ozLXflb8Pf0dp7A= asR9srO19gaOtY4EEyOBMyjZuZD4E-16fwm55zcuzXST7pQ$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!9Ru3u8N6q4gzK-A766p3b7EWawZQ8ozLXflb8Pf0dp7A= asR9srO19gaOtY4EEyOBMyjZuZD4E-16fwm55zcuqt0IAfI$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!9Ru3u8N6q4gzK-A766p3b7EWawZQ8ozLXflb8Pf0dp7A= asR9srO19gaOtY4EEyOBMyjZuZD4E-16fwm55zcuAHeH3Jg$=20

=3D =3D =3D
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FOUS30 KWBC 051924
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
224 PM EST Wed Feb 5 2025

Day 1
Valid 16Z Wed Feb 05 2025 - 12Z Thu Feb 06 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OHIO VALLEY...

...16z Update...

No change to prior reasoning and outlook, other than a minor
adjustment northward to account for the 12z HRRR indicating a
1.5-2.0" stripe of QPF from southwest OH into northern WV and far
southwest PA. Most CAMs are lighter overall with QPF, but a brief
period of embedded training convection is possible, mainly late in
the period (after 06z).=20

Churchill


...Previous Discussion...

No significant changes were made to the Marginal Risk area across
the Ohio Valley. Warm advection showers are expected to break out
over Kentucky, that with the infusion of upper level support and
increasing instability, will allow embedded convection to develop
this afternoon and evening. As the moisture plume turns the front
into a warm front over the Tennessee Valley this evening, expect
the addition of upslope into West Virginia to resulting locally=20
heavier rainfall in the favored areas. Any thunderstorms will be=20
capable of rainfall rates to 1.5 inches per hour. Soils in this=20
area remain nearly saturated and rivers are running high from the=20
rainfall event a few days ago. Thus, the additional rainfall=20
forecast today and tonight, even though amounts will likely be=20
lesser, may still cause isolated flash flooding.

Wegman


Day 2
Valid 12Z Thu Feb 06 2025 - 12Z Fri Feb 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE OHIO VALLEY AND CALIFORNIA...

...OH Valley...
Another round of locally heavy rain is expected Thursday across
portions of KY, TN, WV and far western VA along and ahead of an
approaching cold front. Showers and embedded thunderstorms will
likely be ongoing at 12z and may periodically continue through the
day/evening near the only slowly southward shifting front. While
nothing significant, CAPE upwards of 500-1000 j/kg still seems
likely along this corridor, which should be enough to support
locally heavy rainfall rates. While soil conditions and
streamflows are returning closer to average after the flooding
several days ago, some of this region is still likely more
sensitive than normal to additional heavy rainfall. The latest WPC
QPF is generally 0.75"-1", with two day totals locally exceeding
1.5". Given the instability forecast, it seems reasonable that we
will see isolated totals over 2". While the 00z GEM Reg and FV3LAM
are probably too high with totals, they both do suggest that if
convective coverage can increase enough then some 2-3" amounts can
not be ruled out. Overall expect this rainfall to pose a localized
flood risk.

...California...
After a one day break another system is forecast to move into CA
on Thursday. This is expected to be a pretty dynamic system, with a
strong mid level shortwave and upper level jet. These dynamics
should support a short duration period of enhanced rainfall
rates...although the quick forward motion of the system will limit
overall rainfall magnitudes. Recent model runs are showing some
uptick in rainfall amounts with this system over northern CA, but
still generally looking at totals in the 1-2" range. Given the
saturated conditions and brief potential for higher rates between
00z and 06z, this may be approaching Slight risk levels. Although
will hold off for now as the short duration of these higher rates
may limit the magnitude/coverage of impacts just enough to keep the
risk at Marginal.

The Marginal risk extends southward into Santa Barbara, Ventura and
Los Angeles counties as well. Less rainfall forecast here, but
there is an uptick in IVT into the terrain Thursday night, and PWs
do increase towards and just over 1". Larger scale forcing
generally shears off to the north, but the combination of
increasing PWs, IVT and upslope flow should be enough to result in
a period of moderate to locally heavy rain. We are beginning to
see a slow uptick in rainfall amounts in the models, and so
localized flood impacts are certainly a possibility. Although
given the overall weakening of the system and very little to no
instability, rainfall rates will probably only be high enough to
result in a minor flood risk over just the most sensitive urban
areas or recent burn scar locations.

Chenard

2100 UTC Update

No changes made to the previous marginal risk areas across CA or
from the Upper TN Valley into the Central Appalachians.

Oravec

Day 3
Valid 12Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Oravec


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4knU5ngLok76e5LsAU2OMeRxhT06sEUiJWdFj04JWJ1m= MVHtdZd6QZpOXTbLmI1F6ZgaHtqtLYHzvf9zL0VIjEaKkkw$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4knU5ngLok76e5LsAU2OMeRxhT06sEUiJWdFj04JWJ1m= MVHtdZd6QZpOXTbLmI1F6ZgaHtqtLYHzvf9zL0VIDBxE7Xs$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4knU5ngLok76e5LsAU2OMeRxhT06sEUiJWdFj04JWJ1m= MVHtdZd6QZpOXTbLmI1F6ZgaHtqtLYHzvf9zL0VIdeboCuY$=20

=3D =3D =3D
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FOUS30 KWBC 090808
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
308 AM EST Sun Feb 9 2025

Day 1
Valid 12Z Sun Feb 09 2025 - 12Z Mon Feb 10 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 2
Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 3
Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF=20
THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE
VALLEY...

...ArkLaTex-ArkLaMis into the Mid-South and Tennessee Valley...
Strong NW-SE upper level jet streak will dive southeast into CA
late on Day 3 (Tue night) -- on the western periphery of the=20
longwave trough towards the base. As this occurs, the broad western
U.S. trough will amplify, thereby enhancing the deep-layer ascent
and southwesterly flow/moisture transport within a maturing Warm=20
Conveyor Belt (WCB) downstream across the Mid South-Lower MS Valley
and TN Valley. 850-700 mb moisture flux anomalies increase to 2-3=20
standard deviations above normal Tue-Tue night, while TPW values=20
climb to 1.5-1.75" (around +2 standard deviation above normal). The strengthening dynamical and thermodynamical support will make for=20
efficient rainfall rates despite the lack of deep-layer=20
instability. Much of the guidance, non-CAM at this point being a=20
Day 3 forecast, depicts a widespread swath of 1.5-2.5" of rain=20
within the outlook areas, with more stripes of >3" within the=20
Slight Risk area. Storm motions nearly parallel to the WSW-ENE=20
oriented surface boundary will boost the potential for training,=20
and even though currently the non-CAM guidance is advertising=20
meager deep-layer elevated instability (MUCAPEs generally 250-500=20
J/Kg), believe these values will be amplified somewhat as the event
gets within the high-res CAM windows, again given the dynamic and=20 thermodynamic response to the broad-scale upper trough amplification.

2.00"+/3hr rainfall rates are anticipated where the cells do=20
train, again most likely within the Slight Risk area, which could=20
lead to localized-scattered instances of flash flooding.

Hurley

Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5Vg4A5CEf6psiSAC9G2KkH2dCUUIUt74Lx2o6Gu-_gFT= 5FYYMghMM50QheMWdZwGzVyZwJuFHFX4IYkhnjc8E8Qd8wY$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5Vg4A5CEf6psiSAC9G2KkH2dCUUIUt74Lx2o6Gu-_gFT= 5FYYMghMM50QheMWdZwGzVyZwJuFHFX4IYkhnjc8OA08Q_w$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5Vg4A5CEf6psiSAC9G2KkH2dCUUIUt74Lx2o6Gu-_gFT= 5FYYMghMM50QheMWdZwGzVyZwJuFHFX4IYkhnjc8daFfYqg$=20

=3D =3D =3D
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FOUS30 KWBC 091542
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1042 AM EST Sun Feb 9 2025

Day 1
Valid 16Z Sun Feb 09 2025 - 12Z Mon Feb 10 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Otto


Day 2
Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 3
Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE
VALLEY...

...ArkLaTex-ArkLaMis into the Mid-South and Tennessee Valley...
Strong NW-SE upper level jet streak will dive southeast into CA
late on Day 3 (Tue night) -- on the western periphery of the
longwave trough towards the base. As this occurs, the broad western
U.S. trough will amplify, thereby enhancing the deep-layer ascent
and southwesterly flow/moisture transport within a maturing Warm
Conveyor Belt (WCB) downstream across the Mid South-Lower MS Valley
and TN Valley. 850-700 mb moisture flux anomalies increase to 2-3
standard deviations above normal Tue-Tue night, while TPW values
climb to 1.5-1.75" (around +2 standard deviation above normal). The strengthening dynamical and thermodynamical support will make for
efficient rainfall rates despite the lack of deep-layer
instability. Much of the guidance, non-CAM at this point being a
Day 3 forecast, depicts a widespread swath of 1.5-2.5" of rain
within the outlook areas, with more stripes of >3" within the
Slight Risk area. Storm motions nearly parallel to the WSW-ENE
oriented surface boundary will boost the potential for training,
and even though currently the non-CAM guidance is advertising
meager deep-layer elevated instability (MUCAPEs generally 250-500
J/Kg), believe these values will be amplified somewhat as the event
gets within the high-res CAM windows, again given the dynamic and
thermodynamic response to the broad-scale upper trough amplification.

2.00"+/3hr rainfall rates are anticipated where the cells do
train, again most likely within the Slight Risk area, which could
lead to localized-scattered instances of flash flooding.

Hurley

Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5yGvPYiqo1DR-y9O2HNOTU9HkVHbPZ0ik6vlNaIwxpCe= 56RO7_1oE1gy20yIzf_t_XSX4wbds4KUl2cERzpAZShE2JY$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5yGvPYiqo1DR-y9O2HNOTU9HkVHbPZ0ik6vlNaIwxpCe= 56RO7_1oE1gy20yIzf_t_XSX4wbds4KUl2cERzpAcdhwaPA$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5yGvPYiqo1DR-y9O2HNOTU9HkVHbPZ0ik6vlNaIwxpCe= 56RO7_1oE1gy20yIzf_t_XSX4wbds4KUl2cERzpA66upxHU$=20

=3D =3D =3D
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FOUS30 KWBC 091911
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
211 PM EST Sun Feb 9 2025

Day 1
Valid 16Z Sun Feb 09 2025 - 12Z Mon Feb 10 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Otto


Day 2
Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Oravec

Day 3
Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE
VALLEY...

...ArkLaTex-ArkLaMis into the Mid-South and Tennessee Valley...
Strong NW-SE upper level jet streak will dive southeast into CA
late on Day 3 (Tue night) -- on the western periphery of the
longwave trough towards the base. As this occurs, the broad western
U.S. trough will amplify, thereby enhancing the deep-layer ascent
and southwesterly flow/moisture transport within a maturing Warm
Conveyor Belt (WCB) downstream across the Mid South-Lower MS Valley
and TN Valley. 850-700 mb moisture flux anomalies increase to 2-3
standard deviations above normal Tue-Tue night, while TPW values
climb to 1.5-1.75" (around +2 standard deviation above normal). The strengthening dynamical and thermodynamical support will make for
efficient rainfall rates despite the lack of deep-layer
instability. Much of the guidance, non-CAM at this point being a
Day 3 forecast, depicts a widespread swath of 1.5-2.5" of rain
within the outlook areas, with more stripes of >3" within the
Slight Risk area. Storm motions nearly parallel to the WSW-ENE
oriented surface boundary will boost the potential for training,
and even though currently the non-CAM guidance is advertising
meager deep-layer elevated instability (MUCAPEs generally 250-500
J/Kg), believe these values will be amplified somewhat as the event
gets within the high-res CAM windows, again given the dynamic and
thermodynamic response to the broad-scale upper trough amplification.

2.00"+/3hr rainfall rates are anticipated where the cells do
train, again most likely within the Slight Risk area, which could
lead to localized-scattered instances of flash flooding.

Hurley

2100 UTC update:

At the moment, no significant changes made to the previous outlook
areas. The 12Z model suite is fairly consistent with the previous
guidance.

Oravec



Day 1 threat area:=20 https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt= __;!!DZ3fjg!5dn16GgwCWRdLC7Fnbqrxg9Cgv36qAXDKmFit4cNaP2tl3zzScKQy60eWqTtj4x= BQxFnVrqNug05NU2PKmu-HIETdMs$ Day 2 threat area:=20 https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt= __;!!DZ3fjg!5dn16GgwCWRdLC7Fnbqrxg9Cgv36qAXDKmFit4cNaP2tl3zzScKQy60eWqTtj4x= BQxFnVrqNug05NU2PKmu-vidzg0Q$ Day 3 threat area:=20 https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt= __;!!DZ3fjg!5dn16GgwCWRdLC7Fnbqrxg9Cgv36qAXDKmFit4cNaP2tl3zzScKQy60eWqTtj4x= BQxFnVrqNug05NU2PKmu-a2jKYrs$=20

=3D =3D =3D
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FOUS30 KWBC 100045
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
745 PM EST Sun Feb 9 2025

Day 1
Valid 01Z Mon Feb 10 2025 - 12Z Mon Feb 10 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Pereira


Day 2
Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Oravec

Day 3
Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE
VALLEY...

...ArkLaTex-ArkLaMis into the Mid-South and Tennessee Valley...
Strong NW-SE upper level jet streak will dive southeast into CA
late on Day 3 (Tue night) -- on the western periphery of the
longwave trough towards the base. As this occurs, the broad western
U.S. trough will amplify, thereby enhancing the deep-layer ascent
and southwesterly flow/moisture transport within a maturing Warm
Conveyor Belt (WCB) downstream across the Mid South-Lower MS Valley
and TN Valley. 850-700 mb moisture flux anomalies increase to 2-3
standard deviations above normal Tue-Tue night, while TPW values
climb to 1.5-1.75" (around +2 standard deviation above normal). The strengthening dynamical and thermodynamical support will make for
efficient rainfall rates despite the lack of deep-layer
instability. Much of the guidance, non-CAM at this point being a
Day 3 forecast, depicts a widespread swath of 1.5-2.5" of rain
within the outlook areas, with more stripes of >3" within the
Slight Risk area. Storm motions nearly parallel to the WSW-ENE
oriented surface boundary will boost the potential for training,
and even though currently the non-CAM guidance is advertising
meager deep-layer elevated instability (MUCAPEs generally 250-500
J/Kg), believe these values will be amplified somewhat as the event
gets within the high-res CAM windows, again given the dynamic and
thermodynamic response to the broad-scale upper trough amplification.

2.00"+/3hr rainfall rates are anticipated where the cells do
train, again most likely within the Slight Risk area, which could
lead to localized-scattered instances of flash flooding.

Hurley

2100 UTC update:

At the moment, no significant changes made to the previous outlook
areas. The 12Z model suite is fairly consistent with the previous
guidance.

Oravec



Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt= __;!!DZ3fjg!9qUzcD1EhKtHB2tCSA8FoG2MrqSfo1Gm8_HO9QV95vbZ8mNqtBCil6M_gk6hlce= 8xa-_QJSrRjsusADZU8gpmmuA58s$ Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt= __;!!DZ3fjg!9qUzcD1EhKtHB2tCSA8FoG2MrqSfo1Gm8_HO9QV95vbZ8mNqtBCil6M_gk6hlce= 8xa-_QJSrRjsusADZU8gpfv-6nXo$ Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt= __;!!DZ3fjg!9qUzcD1EhKtHB2tCSA8FoG2MrqSfo1Gm8_HO9QV95vbZ8mNqtBCil6M_gk6hlce= 8xa-_QJSrRjsusADZU8gpaHrRbCk$=20

=3D =3D =3D
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FOUS30 KWBC 110046
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
746 PM EST Mon Feb 10 2025

Day 1
Valid 01Z Tue Feb 11 2025 - 12Z Tue Feb 11 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

...Arklatex/Lower MS Valley into portions of TN/KY...
Strengthening warm air advection/isentropic ascent associated with
gradually backing mid-level flow and an increasing southwest low-
level jet (reaching 30 to 40+ kts) will facilitate the development
and expansion of moderate to locally heavy shower activity tonight
through Tuesday morning along an axis from northeast TX/southeast
OK northeastward through central and northern AR and into areas of central/western TN and southern KY. Some return of weak elevated
instability will support some localized convection that may yield
some hourly rainfall totals of a 0.25" to 0.50" based off the 12Z
HREF guidance, but generally the rainfall totals tonight going
through 12Z/Tuesday should be in the 1 to 2 inch range. Trends will
continue to be monitored, but these modest rainfall rates/totals
at least through early Tuesday are not likely to result in any FFG
exceedance concerns. Any runoff problems are expected to be
isolated at best.

Orrison/Pereira

Day 2
Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE
VALLEY...

20z Update: Main adjustment was to expand the Slight risk to the
southwest into more of eastern TX. We often see convection get
organized further southwest than expected in events like this, and
there is growing QPF signal in the 12z ECMWF, UKMET and Gem Reg
over this area. Will also note that the CSU GEFS based machine
learning guidance also indicates higher probabilities of excessive
rainfall further to the southwest into more of eastern TX and
southwestern LA. The northeastern extent of the Slight risk was
trimmed back a bit over eastern TN and northern GA. Instability
will initially be lacking here which should delay the flash flood
risk...expect the flash flood risk to pick up more over this area
as we head into day 3.

Chenard

...Previous Discussion...

...ArkLaTex-ArkLaMis into the Mid-South and Tennessee Valley...
Increasing coverage of showers and thunderstorms along and ahead of
a well defined cold front trailing a developing area of low
pressure taking shape over the Tennessee Valley will lead to an
increasing threat of excessive rainfall Wednesday into early
Thursday from easter Texas and parts of Arkansas and Louisiana
into the west aspect of the Appalachians of Tennessee and southeast
Kentucky. At the synoptic scale, a broad trough over the western
U.S. will amplify, thereby enhancing the deep-layer ascent and
southwesterly flow/moisture transport over this part of the country
due to a increasing low level flow. 850-700 mb moisture flux
anomalies still look to increase to 2-3 standard deviations above
normal Tuesday/Tuesday night while Precipitable Water values climb
to 1.5-1.75" (around +2 standard deviation above normal). The
strengthening dynamical and thermodynamical support will make for
efficient rainfall rates despite the lack of deep- layer
instability and the exit region of a 125 to 150 kt upper level jet
should aid deep layer vertical ascent. Much of the guidance
generally depicts a widespread swath of 1.5-3" of rain within the
outlook areas, with the most aggressive model being the ECMWF with
maximum values exceeding 4 inches. Storm motions nearly parallel
to the WSW-ENE oriented surface boundary will boost the potential
for training despite meager deep- layer elevated instability
(MUCAPEs generally 250-500 J/Kg). With 2.00"+/3hr rainfall rates
still being anticipated where the cells do train, again most
likely within the Slight Risk area, which could lead to localized-
scattered instances of flash flooding.

Bann

Day 3
Valid 12Z Wed Feb 12 2025 - 12Z Thu Feb 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
TENNESSEE VALLEY INTO THE MID-SOUTH...

20z Update: The prolonged heavy rainfall event will continue
Wednesday into Wednesday night over the Southeast. The extended
duration of this event will lead to storm total rainfall into the
3-5" range, with locally higher totals possible. As stronger
forcing ejects eastward on Wednesday, an increase in the low level
jet should aid in both increasing moisture convergence and
advecting instability northward. Thus higher rainfall rates are
possible...and these higher rates moving over what should be
saturating ground conditions could result in an increased flash
flood risk by later in the period. The best chance of this
occurring is currently over portions of northern AL/GA into far
southeastern TN and the far western Carolinas. Do consider this a
higher end Slight risk over these areas. Can not rule out an
eventual MDT risk upgrade pending model trends over the coming days
and how effective the extended duration of rain is at saturating
what will initially be dry soil and streamflow conditions.

Chenard

...Previous Discussion...

...Tennessee Valley into the Mid-South...
The threat of excessive rainfall will continue on Wednesday and
early Thursday ahead of the same system which brought the
excessive rainfall potential on Tuesday into early Wednesday as a
cold front makes its way eastward. Broad scale ascent will continue
to aided by the southern entrance region of a 135 to 155 kt upper
level jet...while moisture convergence is maximized along a well
defined surface cold front which intercepts a plume of moisture
being pulled northward by a 40 to 50 knot low level jet. There is
still spread in the guidance about placement of where the heaviest
rainfall will occur but amounts generally in the 1 to 3 inch
range...with locally higher amount where any enhanced rainfall
rates set up due to banding/training. Given antecedent
conditions...feel that a Slight risk should suffice.


...California Coast...
The plume of moisture from the Pacific Ocean towards the end of Day
2 will start to bring rain to the coastal areas during the Day 3 period...beginning in northern and central portions of California
on Wednesday that propagates southward during Wednesday night and
Thursday. Present indications are that the heaviest amounts remain
off shore...but a general uptick in amounts was noted over the past
24 hours in this area.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5goGMmzfOCLP-tPdB_Y6bJpzWbeQiFSVADwDCBcbABQU= ESDF4RzK_duE1zI915x8Y_-yxuWa55wdbxYMSKK19MFbfCw$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5goGMmzfOCLP-tPdB_Y6bJpzWbeQiFSVADwDCBcbABQU= ESDF4RzK_duE1zI915x8Y_-yxuWa55wdbxYMSKK1xEUe1YI$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5goGMmzfOCLP-tPdB_Y6bJpzWbeQiFSVADwDCBcbABQU= ESDF4RzK_duE1zI915x8Y_-yxuWa55wdbxYMSKK1wp8HvVM$=20

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FOUS30 KWBC 111925
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
225 PM EST Tue Feb 11 2025

Day 1
Valid 16Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE MID-SOUTH INTO EAST TEXAS...

Some adjustments were made to the Slight and Marginal Risk areas
based on the latest guidance and observational trends. First, the
Slight and Marginal risks were expanded towards the southwest based
on the latest observational and model (12z CAM) trends. This
included an expansion towards the Houston metro region, given that
the probabilities for localized 5" exceedance are maximized (near
10%, per 40-km neighborhood HREF probs) across portions of East TX
(and trends are edging towards the Upper TX Coast itself,
particularly with the 12z HRRR being a southern outlier). While
instability will be maximized across the region, rainfall totals
are still rather spread out between two distinct rounds (one
currently ongoing and largely beneficial, but will prime the soils
for possible isolated to scattered flash flooding with the second
round expected late this evening). Farther northeast into northern
LA, central MS, and far southern AR, instability will be more
limited, but probabilities for 3" exceedance remain high (40-60%,
per 40-km neighborhood HREF probs) and the Slight was maintained.
Even farther northeast into northern AL, the CAMs have trended
lower with expected rainfall (with little to no instability) and
longer term, spread out rainfall totals of 1-2" should result in
little to no impact (though localized flood impacts cannot be ruled
out). The Slight was removed from this region to confine it to the
areas where 3" exceedance are possible.

Churchill


...Previous Discussion...

Few changes needed to the old Day 2 ERO as it propagates into the
Day1 period. Main focus for heavy rainfall and the potential for
excessive rainfall will be along and ahead of a cold front
associated with a developing synoptic scale low pressure system
within a broad/fairly flat flow pattern. Inclusion of more CAM
guidance supports the idea of higher intensity rainfall extending
as far west as eastern Texas...a tendency we often see convection
get organized farther southwest than expected in events like this,
and there is growing QPF signal in the 12z ECMWF, UKMET and Gem Reg
over this area. The Slight risk area extended northeastward where
there is a bit of instability that develops later in the period but
looks to be lacking initially. At expect the flash flood risk to
pick up more over this area as we head into day 2.

Bann


Day 2
Valid 12Z Wed Feb 12 2025 - 12Z Thu Feb 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
TENNESSEE VALLEY INTO THE MID-SOUTH...

...Tennessee Valley into the Mid-South...

Another wave of low pressure will move through the area Wednesday
into Wednesday night, bringing additional widespread precipitation
to the region. Increasing low level moisture combined with the
favorable upper level support should result in robust rainfall with
embedded convection. An axis of 2 to 3 inches is expected during
the 24-hour period from portions of Louisiana through southwest
North Carolina. Embedded within that will be the possibility of
higher amounts, most likely over portions of Alabama and Georgia
where the overlap of available instability and potential for
training/repeating rounds of rainfall appear most likely. Combined
with the preceding day rainfall, 48-hour totals exceeding 3-5" will
be possible and this will likely lead to excessive runoff and
increasing soil saturation. As a result, a higher end Slight Risk
in the ERO is maintained, with the greatest risk for flash flooding
over portions AL/GA.

...California Coast...
The beginning of the active/wet period for the West Coast begins
late in the period as the initial surge of atmospheric moisture
arrives after 00Z Thursday across coastal central California. This
will bring the initial threat of flooding, though the bulk/peak of
it will be in the Day 3 /Thursday/ period.=20=20

Taylor


Day 3
Valid 12Z Thu Feb 13 2025 - 12Z Fri Feb 14 2025

..THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL PARTS OF THE
SOUTHERN CALIFORNIA COAST...

...California...
The peak of the atmospheric river is expected during this period
with the initial focus on coastal central California at the start=20
of the period, then the best IVT shifts southward through the=20
period, reaching southern California by the end of the period=20
Thursday night. IVT values from the GFS peak at around 600-700=20
kg/m/s initially along the central coast then settle around=20
400-500 kg/m/s as the AR reaches SoCal. The greatest QPF amounts=20
will be confined to the coastal terrain areas as well as for the=20
Sierra. Total amounts for the 24-hour period look to be between=20
1-3" with the favored terrain areas and peaks topping out between=20
4-5".=20

The primary concern is the potential for damaging and potentially life-threatening burn scar flash flooding and debris flows,
particularly for southern California where the Moderate Risk (Level
3/4) is in place. Even outside the burn scar regions, the intense
rain rates and rainfall totals over the highly urbanized area could
bring scattered to numerous instances of flash flooding. Elsewhere,
a broad Slight Risk (Level 2/4) exists for much of the coastal=20
ranges as well as the Central Valley and lower elevations of the=20
Sierra Nevada.=20

There is a Moderate Risk of excessive rainfall over portions of=20
the Southern California coast embedded within a broader Slight risk
of excessive rainfall covering much of the central and southern=20
California coast. An atmospheric river is expected to skirt the=20
coast as it makes its way south and east. The primary concern is=20
for damaging flooding and debris flow from the numerous fresh burn=20
scars in the region given the 24-hour QPF in the 1.5 to 3.5 inch=20 range...with potentially localized higher amounts. In=20
addition...the area is highly urbanized and an environment in which
much of the rainfall will turn immediately to runoff. Farther=20
north...the Slight risk was extended into portions of the=20
Sacramento Valley and San Joaquin Valley...where QPF is not=20
expected to be as great but the conditions have been wetter and=20
soils are more saturated than soils farther south.

...Florida Panhandle and Southern Georgia...
Lingering heavy rainfall will continue Thursday across portions of
the Florida Panhandle and southern Georgia, ahead of the
approaching cold front. Rainfall amounts look to be generally in
the 1-3" range, with some potential for localized rain rates
sufficiently high enough to cause some urban/localized flooding
concerns.=20

Taylor


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5R9c1xHXaDnp1gTTjyGRXmFp1yugiXJwDMeJcNVCiZ9Q= leFn0RchbKxjyWnnklSMKWdvz7O92zHBLlntopQilcx488I$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5R9c1xHXaDnp1gTTjyGRXmFp1yugiXJwDMeJcNVCiZ9Q= leFn0RchbKxjyWnnklSMKWdvz7O92zHBLlntopQiTIEbGs0$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5R9c1xHXaDnp1gTTjyGRXmFp1yugiXJwDMeJcNVCiZ9Q= leFn0RchbKxjyWnnklSMKWdvz7O92zHBLlntopQiQkl4MxM$=20

=3D =3D =3D
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FOUS30 KWBC 120056
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
756 PM EST Tue Feb 11 2025

Day 1
Valid 01Z Wed Feb 12 2025 - 12Z Wed Feb 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
EASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY...

A Slight risk remains for portions of eastern TX into
central/northern LA, far southern AR and western MS. A shortwave=20
and upper jet moving into TX will support increased ascent and the=20 development of another round of convection tonight into Wednesday.=20
A strengthening low level jet is also anticipated, which will=20
result in increased moisture and instability being drawn northward,
along with an uptick in moisture convergence. The ingredients are=20
in place for organized convective development with heavy rainfall=20
rates. Activity will likely initiate over central TX this evening=20
and should be quick moving off to the east. This quick movement=20
will be a limiting factor for flash flooding, but hourly rainfall=20
could still locally approach 2", which could drive at least an=20
isolated flash flood threat...especially over areas that have seen=20
lowered FFG from rainfall earlier today and/or more sensitive urban
areas.=20

By later tonight into Wednesday morning we may begin to see more=20
convective development along the warm front downstream of the area=20
of organized convection. This could allow for some west to east=20
training to occur, locally increasing the flash flood risk over=20
portions of far east TX into LA. The system as a whole remains=20
progressive, which will put a cap on the magnitude/coverage of the=20
flood risk. However the strong dynamics combined with a=20
strengthening west to east oriented axis of lower level moisture=20
convergence supports some training potential by later tonight and=20
an isolated to scattered flash flood risk.

To the east, locally heavy convection may drop a quick 1-2" of=20
rain over portions of central AL and GA, but this should not pose=20
more than a localized flash flood risk. Lighter rain rates will=20
continue across portions of northern AL/GA and into portions of TN=20
and the western Carolinas. Not expecting much of a flash flood risk
here, but the prolonged moderate rainfall may result in some minor
areal flood concerns.

Chenard


Day 2
Valid 12Z Wed Feb 12 2025 - 12Z Thu Feb 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
TENNESSEE VALLEY INTO THE MID-SOUTH...

...Tennessee Valley into the Mid-South...

Another wave of low pressure will move through the area Wednesday
into Wednesday night, bringing additional widespread precipitation
to the region. Increasing low level moisture combined with the
favorable upper level support should result in robust rainfall with
embedded convection. An axis of 2 to 3 inches is expected during
the 24-hour period from portions of Louisiana through southwest
North Carolina. Embedded within that will be the possibility of
higher amounts, most likely over portions of Alabama and Georgia
where the overlap of available instability and potential for
training/repeating rounds of rainfall appear most likely. Combined
with the preceding day rainfall, 48-hour totals exceeding 3-5" will
be possible and this will likely lead to excessive runoff and
increasing soil saturation. As a result, a higher end Slight Risk
in the ERO is maintained, with the greatest risk for flash flooding
over portions AL/GA.

...California Coast...
The beginning of the active/wet period for the West Coast begins
late in the period as the initial surge of atmospheric moisture
arrives after 00Z Thursday across coastal central California. This
will bring the initial threat of flooding, though the bulk/peak of
it will be in the Day 3 /Thursday/ period.

Taylor


Day 3
Valid 12Z Thu Feb 13 2025 - 12Z Fri Feb 14 2025

..THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL PARTS OF THE
SOUTHERN CALIFORNIA COAST...

...California...
The peak of the atmospheric river is expected during this period
with the initial focus on coastal central California at the start
of the period, then the best IVT shifts southward through the
period, reaching southern California by the end of the period
Thursday night. IVT values from the GFS peak at around 600-700
kg/m/s initially along the central coast then settle around
400-500 kg/m/s as the AR reaches SoCal. The greatest QPF amounts
will be confined to the coastal terrain areas as well as for the
Sierra. Total amounts for the 24-hour period look to be between
1-3" with the favored terrain areas and peaks topping out between
4-5".

The primary concern is the potential for damaging and potentially life-threatening burn scar flash flooding and debris flows,
particularly for southern California where the Moderate Risk (Level
3/4) is in place. Even outside the burn scar regions, the intense
rain rates and rainfall totals over the highly urbanized area could
bring scattered to numerous instances of flash flooding. Elsewhere,
a broad Slight Risk (Level 2/4) exists for much of the coastal
ranges as well as the Central Valley and lower elevations of the
Sierra Nevada.

There is a Moderate Risk of excessive rainfall over portions of
the Southern California coast embedded within a broader Slight risk
of excessive rainfall covering much of the central and southern
California coast. An atmospheric river is expected to skirt the
coast as it makes its way south and east. The primary concern is
for damaging flooding and debris flow from the numerous fresh burn
scars in the region given the 24-hour QPF in the 1.5 to 3.5 inch
range...with potentially localized higher amounts. In
addition...the area is highly urbanized and an environment in which
much of the rainfall will turn immediately to runoff. Farther
north...the Slight risk was extended into portions of the
Sacramento Valley and San Joaquin Valley...where QPF is not
expected to be as great but the conditions have been wetter and
soils are more saturated than soils farther south.

...Florida Panhandle and Southern Georgia...
Lingering heavy rainfall will continue Thursday across portions of
the Florida Panhandle and southern Georgia, ahead of the
approaching cold front. Rainfall amounts look to be generally in
the 1-3" range, with some potential for localized rain rates
sufficiently high enough to cause some urban/localized flooding
concerns.

Taylor


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5mPBbwXDTu9S_Os7z2R78zojVwY0UBQLGREeQ4mag062= VtOHaobYGlHN06TQD4v27vhnTKSbdRMtpsug72mdDFk9NjI$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5mPBbwXDTu9S_Os7z2R78zojVwY0UBQLGREeQ4mag062= VtOHaobYGlHN06TQD4v27vhnTKSbdRMtpsug72mdxv5Ykxc$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5mPBbwXDTu9S_Os7z2R78zojVwY0UBQLGREeQ4mag062= VtOHaobYGlHN06TQD4v27vhnTKSbdRMtpsug72mdjm6QWjQ$=20

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FOUS30 KWBC 131604
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1104 AM EST Thu Feb 13 2025

Day 1
Valid 16Z Thu Feb 13 2025 - 12Z Fri Feb 14 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF SOUTHERN CALIFORNIA...

16Z Update...

Changes to the previous outlooks were rather minor overall which
includes removal of the Marginal Risk area across the Southeast
given the downward trends in organized convection and a slackening
of the rainfall rates. While some locally heavy showers and
thunderstorms will still be likely this afternoon ahead of a cold
front, the totals should be rather modest.

Over California, a well-defined/organized deep layer cyclone and=20
associated atmospheric river continues to impact the region. While
the overall deeper layer axis/fetch of strong moisture transport
has settled south of northern California and the Bay Area, there
will be post-frontal convective showers arriving through the
afternoon which will be capable of producing heavy rainfall rates
of 0.50"+/hour. Therefore a Slight Risk is maintained along the
coastal range of northern California coastal range. We have opted
to remove it however for portions of the Sacramento Valley where
the additional totals for today should be rather modest.

No changes farther south down the coast into southern California
where there will be significant sensitivities around the recent
burn scar activity closer into Los Angeles Basin. The latest HREF
guidance supports 0.50" to 1.0"/hour rainfall rates this afternoon
into the evening hours as strong moisture flux and a corridor of
modest instability arrives which coupled with upslope flow into the
Transverse and Peninsular Ranges will support elevated rates=20
including pockets of convection. Therefore the Moderate Risk
remains in place. Please consult WPC's latest MPDs for more=20
details on the shsort-term trends/impacts over the next 6 to 12=20
hours.

Orrison

Previous discussion...

...California...
Overall, not much change to the previous forecast, with the
unfolding atmospheric river expected to peak near the start of the
period. A long warm front currently extending along the coast is
expected to press inland this morning, with IVTs climbing to around
700-800 kg/m/s near the upstream cold front as it approaches the
coast later this morning. The strongest moisture flux is expected
to center near SF Bay at the start of the period, before steadily
shifting south along the coast today. Models continue to show IVTs
decreasing as the axis moves south, dropping to around 400-500
kg/m/s as the AR reaches Southern California later this afternoon
into the evening. Guidance has remained fairly consistent,
indicating precipitation amounts of 4-6 inches along the central to
southern coastal ranges and the Sierra Nevada, falling mostly as
rain below 6000 ft.

A Moderate Risk (level 3/4) remains in place across portions
Southern California, from Santa Barbara County southeastward into
the San Gabriel and San Bernadino mountains, where damaging and
potentially life-threatening burn scar flash flooding and debris
flows remain a primary concern. Even outside of the burn scar areas,
intense rain rates over complex terrain and urban areas may produce
scattered to numerous instances of flash flooding. Elsewhere, a
broad Slight Risk (Level 2/4) exists for much of the remaining
coastal ranges as well as parts of the Central Valley and the lower
elevations of the Sierra Nevada.

...Florida Panhandle and Southern Georgia...

Lingering heavy rainfall will continue this morning across
portions of the Florida Panhandle and southern Georgia ahead of an
approaching cold front. HREF neighborhood probabilities indicate
that additional rainfall amounts of 1-2 inches are likely within
the highlighted area, with some potential for localized rain rates
high enough to cause some urban/localized flooding concerns.

Pereira


Day 2
Valid 12Z Fri Feb 14 2025 - 12Z Sat Feb 15 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MID-SOUTH...

...Mid-South...

Although most of the convective activity, and thus heavy rainfall
threat, in the region should be concentrated in the Day 3 period
(after 12Z Saturday), model guidance does indicate that convection
is likely to begin blossoming late Friday Night. Conditions will
become increasingly favorable after 06Z Saturday with a strong 55-65
knot low-level jet expanding east from the Plains, and significant
northward moisture transport leading to rapid moistening of the
boundary layer. MUCAPE values of around 500-1000 j/kg should support
organized convection with the potential for rainfall rates in excess
of 1 inch per hour at times. Although there is a lack of a
significant front or boundary to help organize a band of convection,
the strength of the LLJ may support backbuilding within a broad zone
of developing convective clusters. This may be enough for some brief
training and a ramp-up in flash flood potential prior to 12Z
Saturday. The 00Z runs of the NAM Nest and FV3 show more widespread
convection than other models; if this trend persists as additional
hi-res guidance becomes available, an expansion of the Marginal Risk
and/or the addition of a Slight Risk area may become warranted with
time.

...Southern California...

The Marginal Risk was removed for southern California given a more
limited QPF signal on the latest guidance, and hi-res models in
excellent agreement on a lack of organized convection. The bulk of
the threat should be in the Day 1 period.

Lamers


Day 3
Valid 12Z Sat Feb 15 2025 - 12Z Sun Feb 16 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE TENNESSEE AND OHIO VALLEYS AND THE CENTRAL APPALACHIANS...

...Ohio and Tennessee Valleys...

Confidence remains high in significant rainfall-related impacts on
Saturday and Saturday Night with model guidance in excellent
agreement depicting a swath of 3-6 inches of rainfall in the 24-hour
period across the region. Although models vary slightly with the
placement, they almost unanimously depict a corridor of heavy rain
about 750mi long centered somewhere in TN/KY. This same region has
generally seen above average precipitation in recent weeks, with the
14-day precip in much of KY, N TN, WV, and W VA at least double the
normal values. The confluence of these factors should make the
region especially vulnerable to flooding from the predicted
rainfall. For additional context on the current hydrologic picture
across the region, refer to the National Hydrologic Discussion from
the National Water Center at water.noaa.gov.

Convection may be ongoing at the beginning of the forecast period
and should become increasingly focused along a developing warm front
to the east of a surface low that will be emerging out of the Plains
on Saturday. The front will be positioned on the nose of very strong
SW, or even WSW, inflow, which should favor backbuilding and
training and a corridor of very heavy rainfall. The environment will
be atypical of mid-February with PWATs reaching around 1.5 inches
and MUCAPE of 500-1000 j/kg. For example, the Nashville sounding
archive exists back to 1948 and they've only ever reached 1000 j/kg
MUCAPE once in February, and 1.5 inch PWATs a few times. The
environment will support rainfall rates in excess of 1 inch per
hour, and given the potential for training and backbuilding, these
rates may be sustained for several hours in some locations. These
would be the areas of greatest concern for flash flooding -- not
only in terms of likelihood but severity -- particularly if the
higher rain rates are sustained over urban areas or vulnerable
terrain for extended periods of time.

The inherited Moderate Risk was mostly maintained as-is with a
slight expansion to the southwest in the vicinity of Memphis, TN;
and a more significant expansion eastward into S WV and W VA. The WV-
VA border region just received some significant snowfall, and model
guidance indicates a fairly high probability of warm, moist air (dew
points in excess of 45 degrees) accompanying the rainfall into this
area, which may lead to a combination of runoff from rain and snow
melt.

It's worth noting a couple additional things. First, the amount of
rain forecast from E KY into S WV and W VA in particular is quite
unusual for the heart of the winter season. Calendar day precip
records across that area for January and February are generally in
the 2-3 inch range, and NBM probabilities indicate it is likely (60+
percent chance) we will see these types of 24-hour rainfall totals
in those areas. Second, this relatively rare winter rain event would
be delivered to an area that has been quite wet recently, and in
some areas has snow on the ground. And third, the high-end scenarios
in much of the Moderate Risk area would be significant by historical
standards. The NBM 90th percentile from N TN into S/E KY and S WV is
on par with the top several wettest days (for any season!) in the
station records in the area. This corridor is where the greatest
concern for severe impacts exists, and it's possible an upgrade to
High Risk may be needed for portions of the area in subsequent
updates.

Lamers

Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!43L8ucsEtO7RJhume0wxnLsmL5KsdpEM_hpFXNpYlRPe= BhG0cg_iAjCkLRQJM1yCyUqY5gJRtUPyZuurz4Lebvy8tHk$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!43L8ucsEtO7RJhume0wxnLsmL5KsdpEM_hpFXNpYlRPe= BhG0cg_iAjCkLRQJM1yCyUqY5gJRtUPyZuurz4LeAgyB_Rc$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!43L8ucsEtO7RJhume0wxnLsmL5KsdpEM_hpFXNpYlRPe= BhG0cg_iAjCkLRQJM1yCyUqY5gJRtUPyZuurz4LeCVuujkY$=20

=3D =3D =3D
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FOUS30 KWBC 132015
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
315 PM EST Thu Feb 13 2025

Day 1
Valid 16Z Thu Feb 13 2025 - 12Z Fri Feb 14 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF SOUTHERN CALIFORNIA...

16Z Update...

Changes to the previous outlooks were rather minor overall which
includes removal of the Marginal Risk area across the Southeast
given the downward trends in organized convection and a slackening
of the rainfall rates. While some locally heavy showers and
thunderstorms will still be likely this afternoon ahead of a cold
front, the totals should be rather modest.

Over California, a well-defined/organized deep layer cyclone and
associated atmospheric river continues to impact the region. While
the overall deeper layer axis/fetch of strong moisture transport
has settled south of northern California and the Bay Area, there
will be post-frontal convective showers arriving through the
afternoon which will be capable of producing heavy rainfall rates
of 0.50"+/hour. Therefore a Slight Risk is maintained along the
coastal range of northern California coastal range. We have opted
to remove it however for portions of the Sacramento Valley where
the additional totals for today should be rather modest.

No changes farther south down the coast into southern California
where there will be significant sensitivities around the recent
burn scar activity closer into Los Angeles Basin. The latest HREF
guidance supports 0.50" to 1.0"/hour rainfall rates this afternoon
into the evening hours as strong moisture flux and a corridor of
modest instability arrives which coupled with upslope flow into the
Transverse and Peninsular Ranges will support elevated rates
including pockets of convection. Therefore the Moderate Risk
remains in place. Please consult WPC's latest MPDs for more
details on the short-term trends/impacts over the next 6 to 12=20
hours.

Orrison

Previous discussion...

...California...

Overall, not much change to the previous forecast, with the
unfolding atmospheric river expected to peak near the start of the
period. A long warm front currently extending along the coast is
expected to press inland this morning, with IVTs climbing to around
700-800 kg/m/s near the upstream cold front as it approaches the
coast later this morning. The strongest moisture flux is expected
to center near SF Bay at the start of the period, before steadily
shifting south along the coast today. Models continue to show IVTs
decreasing as the axis moves south, dropping to around 400-500
kg/m/s as the AR reaches Southern California later this afternoon
into the evening. Guidance has remained fairly consistent,
indicating precipitation amounts of 4-6 inches along the central to
southern coastal ranges and the Sierra Nevada, falling mostly as
rain below 6000 ft.

A Moderate Risk (level 3/4) remains in place across portions
Southern California, from Santa Barbara County southeastward into
the San Gabriel and San Bernadino mountains, where damaging and
potentially life-threatening burn scar flash flooding and debris
flows remain a primary concern. Even outside of the burn scar areas,
intense rain rates over complex terrain and urban areas may produce
scattered to numerous instances of flash flooding. Elsewhere, a
broad Slight Risk (Level 2/4) exists for much of the remaining
coastal ranges as well as parts of the Central Valley and the lower
elevations of the Sierra Nevada.

...Florida Panhandle and Southern Georgia...

Lingering heavy rainfall will continue this morning across
portions of the Florida Panhandle and southern Georgia ahead of an
approaching cold front. HREF neighborhood probabilities indicate
that additional rainfall amounts of 1-2 inches are likely within
the highlighted area, with some potential for localized rain rates
high enough to cause some urban/localized flooding concerns.

Pereira


Day 2
Valid 12Z Fri Feb 14 2025 - 12Z Sat Feb 15 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MID-SOUTH...

2030Z Update...

Only very modest adjustments were made to the previous forecast
which includes some minor expansion of the Marginal Risk area
across the Mid-South. Heavy showers and thunderstorms will be
developing and expanding in coverage late Friday night and early
Saturday morning across central/eastern AR along with the MO
Bootheel which will be advancing downstream in a southwest to
northeast fashion across western TN and western KY. Increasing
elevated CAPE/warm air advection associated with a strengthening
southwest low-level jet (40 to 60+ kts by 12Z/Sat) along with
enhancing moisture transport ahead of a deep layer trough
approaching the southern High Plains will facilitate this
convective evolution. The latest guidance has tended to trend
toward a somewhat earlier convective footprint, and that would
facilitate a slightly wetter scenario especially in the last 6
hours of this period, and so it is possible that an upgrade to a
Slight Risk may need to be considered locally with later updates.

Orrison

Previous discussion...

...Mid-South...

Although most of the convective activity, and thus heavy rainfall
threat, in the region should be concentrated in the Day 3 period
(after 12Z Saturday), model guidance does indicate that convection
is likely to begin blossoming late Friday Night. Conditions will
become increasingly favorable after 06Z Saturday with a strong 55-65
knot low-level jet expanding east from the Plains, and significant
northward moisture transport leading to rapid moistening of the
boundary layer. MUCAPE values of around 500-1000 j/kg should support
organized convection with the potential for rainfall rates in excess
of 1 inch per hour at times. Although there is a lack of a
significant front or boundary to help organize a band of convection,
the strength of the LLJ may support backbuilding within a broad zone
of developing convective clusters. This may be enough for some brief
training and a ramp-up in flash flood potential prior to 12Z
Saturday. The 00Z runs of the NAM Nest and FV3 show more widespread
convection than other models; if this trend persists as additional
hi-res guidance becomes available, an expansion of the Marginal Risk
and/or the addition of a Slight Risk area may become warranted with
time.

...Southern California...

The Marginal Risk was removed for southern California given a more
limited QPF signal on the latest guidance, and hi-res models in
excellent agreement on a lack of organized convection. The bulk of
the threat should be in the Day 1 period.

Lamers


Day 3
Valid 12Z Sat Feb 15 2025 - 12Z Sun Feb 16 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE TENNESSEE AND OHIO VALLEYS AND THE CENTRAL APPALACHIANS...

2030Z Update...

At least on the synoptic scale, no changes to the previous thinking
with respect to what is expected to be a high-impact flash flood
event across areas of the TN/OH Valleys and possibly the central=20 Appalachians during the day Saturday through Saturday night. The
latest global model consensus/NBM guidance continues to support an
event capable of producing a relatively widespread 3 to 6+ inch
rainfall event in a general southwest to northeast fashion across
the region. There has been just a bit of a trend southwestward with
the corridor of heaviest rainfall, but with concerns for a=20 widespread/organized convective outbreak across portions of the
Lower MS Valley/Mid-South, there may tend to be some additional
trends in the guidance for heavier rains somewhat farther south.
This would account for the likelihood of supercell thunderstorm and
QLCS evolutions. Therefore, some modest adjustment of the Slight
and Moderate Risk have been accommodated, however, for parts of the
central Appalachians, the Moderate Risk are was expanded a bit
farther north to account for extreme hydrological sensitivities
antecedently and especially with a melting snowpack concern.

The preference was to hold off on a High Risk upgrade today pending arrival/inclusion of the HREF guidance and its handling of this
event which may necessitate spatially a different placement of it relative
to where the NBM/global models would currently tend to favor it.
Also, it is possible that the HREF CAM solutions may locally favor
even heavier totals (i.e. 6+ inch storm totals) given an excellent
set-up for training convection with high rainfall rates up to
2+"/hour. Synoptically, this has the hallmarks of being a high-end
Maddox-type flash flood event regardless of where exactly the=20
heaviest totals occur.

Orrison

Previous discussion...

...Ohio and Tennessee Valleys...

Confidence remains high in significant rainfall-related impacts on
Saturday and Saturday Night with model guidance in excellent
agreement depicting a swath of 3-6 inches of rainfall in the 24-hour
period across the region. Although models vary slightly with the
placement, they almost unanimously depict a corridor of heavy rain
about 750mi long centered somewhere in TN/KY. This same region has
generally seen above average precipitation in recent weeks, with the
14-day precip in much of KY, N TN, WV, and W VA at least double the
normal values. The confluence of these factors should make the
region especially vulnerable to flooding from the predicted
rainfall. For additional context on the current hydrologic picture
across the region, refer to the National Hydrologic Discussion from
the National Water Center at water.noaa.gov.

Convection may be ongoing at the beginning of the forecast period
and should become increasingly focused along a developing warm front
to the east of a surface low that will be emerging out of the Plains
on Saturday. The front will be positioned on the nose of very strong
SW, or even WSW, inflow, which should favor backbuilding and
training and a corridor of very heavy rainfall. The environment will
be atypical of mid-February with PWATs reaching around 1.5 inches
and MUCAPE of 500-1000 j/kg. For example, the Nashville sounding
archive exists back to 1948 and they've only ever reached 1000 j/kg
MUCAPE once in February, and 1.5 inch PWATs a few times. The
environment will support rainfall rates in excess of 1 inch per
hour, and given the potential for training and backbuilding, these
rates may be sustained for several hours in some locations. These
would be the areas of greatest concern for flash flooding -- not
only in terms of likelihood but severity -- particularly if the
higher rain rates are sustained over urban areas or vulnerable
terrain for extended periods of time.

The inherited Moderate Risk was mostly maintained as-is with a
slight expansion to the southwest in the vicinity of Memphis, TN;
and a more significant expansion eastward into S WV and W VA. The WV-
VA border region just received some significant snowfall, and model
guidance indicates a fairly high probability of warm, moist air (dew
points in excess of 45 degrees) accompanying the rainfall into this
area, which may lead to a combination of runoff from rain and snow
melt.

It's worth noting a couple additional things. First, the amount of
rain forecast from E KY into S WV and W VA in particular is quite
unusual for the heart of the winter season. Calendar day precip
records across that area for January and February are generally in
the 2-3 inch range, and NBM probabilities indicate it is likely (60+
percent chance) we will see these types of 24-hour rainfall totals
in those areas. Second, this relatively rare winter rain event would
be delivered to an area that has been quite wet recently, and in
some areas has snow on the ground. And third, the high-end scenarios
in much of the Moderate Risk area would be significant by historical
standards. The NBM 90th percentile from N TN into S/E KY and S WV is
on par with the top several wettest days (for any season!) in the
station records in the area. This corridor is where the greatest
concern for severe impacts exists, and it's possible an upgrade to
High Risk may be needed for portions of the area in subsequent
updates.

Lamers

Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5kD0EeF2X25cStof384W-5AYuKr6-bjxr1PTndBhppP4= 9RFL8w9_eXL0dzPiSjXug4NpZL5vDp8kRZ8MHj5wfe06UTI$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5kD0EeF2X25cStof384W-5AYuKr6-bjxr1PTndBhppP4= 9RFL8w9_eXL0dzPiSjXug4NpZL5vDp8kRZ8MHj5whlNLUrU$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5kD0EeF2X25cStof384W-5AYuKr6-bjxr1PTndBhppP4= 9RFL8w9_eXL0dzPiSjXug4NpZL5vDp8kRZ8MHj5wX9MOBts$=20

=3D =3D =3D
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FOUS30 KWBC 141925
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
225 PM EST Fri Feb 14 2025

Day 1
Valid 16Z Fri Feb 14 2025 - 12Z Sat Feb 15 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE MID-SOUTH...

16Z Update: No significant changes were made to the risk area, some
broadening to account for some of the model variability and latest
HREF probabilities. Otherwise, the risk area looks good leading
into the more significant heavy rainfall threat for the current Day
2 period.

---previous discussion---

Models continue to show ingredients coming together late in the
period to support a developing heavy rain that will evolve into a
much larger threat on Day 2. Deepening moisture coincident with a
southwesterly 50 kt low level jet, interacting with mid-level
energy, is expected to support showers and storms developing
across the region Saturday morning. There is some signal in the hi-res
models showing storms beginning to train, raising an increasing
threat for heavy accumulations near the end of the period. While
widespread heavy amounts are not expected prior to 12Z, this
continued signal in some of the guidance for training storms with
locally heavy amounts beginning to develop, warranted leaving the
Marginal Risk in place across portions of the region. However, the
areal extent of the risk was reduced some from the previous,
confining the area mostly to where the 00Z HREF showed the highest
neighborhood probabilities for accumulations of an inch or more.

Pereira/Taylor

Day 2
Valid 12Z Sat Feb 15 2025 - 12Z Sun Feb 16 2025

...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE
TENNESSEE AND OHIO VALLEYS...

...Ohio and Tennessee Valleys...

Confidence in a very impactful, life-threatening and significant=20
heavy rainfall and flash flood event remains high beginning late=20
tonight through Saturday night across portions of the Ohio and=20
Tennessee Valleys. While there is some subtle variability in the=20
placement of the heaviest QPF (northwest to southeast), some=20
clustering of the guidance happened this cycle for a swath of 3-6"=20
from western TN through central Kentucky with a signal for isolated
amounts up to 8".=20

The environment will be quite unusual for mid-February. The
combination of MUCAPE of 500-1000 j/kg and PWATs reaching around 1.5
inches has only rarely been observed in KY/TN at this time of year,
and would be supportive of 1-2 inch per hour rain rates in the most
organized and intense convection. A powerful southwesterly LLJ over
60 knots, oriented at an acute angle to the developing warm front,
will favor backbuilding into the region of stronger instability. And
the overall mean flow should favor some periods of training
convective clusters or bands near the warm front and surface low
track. All of these ingredients are fairly classic for impactful
flash flooding cases, and significant impacts are anticipated in=20
this one as well.

Given all of this, a High Risk was introduced for portions of NW TN
through central KY, where life-threatening and significant flooding
is anticipated.=20

Elsewhere, not many changes were made to the Moderate/Slight Risk
areas, with some pulling back out of eastern KY and the central
Appalachians where the trends for less QPF continues somewhat.
However, don't want to downplay that area given its sensitivity=20
and antecedent conditions as well.=20

Lamers/Taylor

Day 3
Valid 12Z Sun Feb 16 2025 - 12Z Mon Feb 17 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN PORTIONS OF THE MID-ATLANTIC...

...Mid-Atlantic...

A Marginal Risk was maintained across portions of the Mid-Atlantic
region back toward the central Appalachians on Sunday, primarily=20
due to the potential for briefly heavy rain rates with convection=20
along an advancing cold front, and fairly low flash flood guidance=20
values. The speed of the cold front should reduce the duration of=20
any heavy rain, and thus any flash flood threat should remain=20
rather isolated, however some portions of the area, particularly
southwest Virginia is very saturated due to recent heavy
precipitation events.=20

Lamers/Taylor


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_LQL5f_gVvJpie7cnnLj15sZqmJ5jesolL6-LT5MqZRx= jMidKsPAXsc0E2SZZ5tlNZ8RBW6aYcqhWnussJBkMtITpzs$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_LQL5f_gVvJpie7cnnLj15sZqmJ5jesolL6-LT5MqZRx= jMidKsPAXsc0E2SZZ5tlNZ8RBW6aYcqhWnussJBkozlB9mc$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_LQL5f_gVvJpie7cnnLj15sZqmJ5jesolL6-LT5MqZRx= jMidKsPAXsc0E2SZZ5tlNZ8RBW6aYcqhWnussJBkP7eu_mI$=20

=3D =3D =3D
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FOUS30 KWBC 040827
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
327 AM EST Tue Feb 4 2025

Day 1
Valid 12Z Tue Feb 04 2025 - 12Z Wed Feb 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF=20
CENTRAL AND NORTHERN CALIFORNIA...

A large and energetic cutoff low that will remain largely stationary=20
off the coast of Vancouver Island will be the upper level animus for=20
the active weather ongoing across California today. An atmospheric=20
river event that has been ongoing for the past several days will=20
come to an end (or at least take a significant break) during this=20
period. However, to get to the break, one last potent area of low=20
pressure moving along the atmospheric river still has to move across=20 California, resulting in another period of heavy rain. The cold air=20 following behind its cold front will push the AR far enough south=20
but also far enough away from the forcing to cause it to mostly=20
dissipate tonight.

The atmospheric river currently is located along the I-80 corridor=20
from San Francisco through Lake Tahoe. It is expected to shift south=20
to about a Monterey to Modesto line, leaving the I-80 corridor in=20
periodic shower activity. It will not move much along the foothills=20
of the Sierras, where upslope flow will keep the steady rain going=20
well north of where the core of the atmospheric river is. From the=20
Bay Area north along the coast, expect a break from the rainfall=20
through until about 15Z/7am PST. That all changes beyond 15Z, when=20
the aforementioned low begins to move ashore, resulting in steady=20
rain for the almost the entire northern half of California. As in=20
previous days, localized convective enhancement and convergence=20
bands are expected to develop within the broader rainfall shield.=20
This will be supported by a strengthening LLJ through the Sacramento=20
Valley, which will intensify due to the approach of the southerly=20
flow ahead of the low. Colder and drier air following behind the low=20
will begin to clear the precipitation out from northwest to=20
southeast starting around 22Z/2pm PST. Until the back edge clears,=20
locally heady rain will continue, which will be enhanced by the=20
passage of the surface cold front itself, bringing a brief period of=20
heavy rain for most of northern California during the late afternoon=20
and evening hours, potentially impacting this evening's commute.

After about sunset or so, the entire atmospheric river will weaken,=20
though the prevailing southwesterly upslope flow may continue much=20
lighter rain into the Transverse Ranges, the southern Sierras, and=20 eventually the Los Angeles Metro area. Despite the recent fires in=20
that area, the rain should be light enough east of Santa Barbara=20
County that there should not be enough to cause flooding concerns,=20
so the light rain from the showers should be beneficial, if not=20
nearly enough to dent the ongoing drought conditions in southern=20
California.

All of the guidance has shifted significantly northward with the=20
track of the incoming low for the day today. This resulted in a=20
northward shift in the ERO risk areas, with the Slight Risk being=20
expanded well up the coast to Mendocino County and all of the=20
northern Coast Ranges and trimmed out of the southern Central=20
Valley. An internal higher-end Slight was added to most of the=20
foothills of the northern Sierras since this area stands to pick up=20
an additional 3-5 inches of rain on top of the foot+ they've seen=20
the past few days.=20

The ERO trimming was due to rain shadowing from the southern Coast=20
Ranges. Unlike previous days, the southern Coast Ranges from the=20
Santa Cruz Mountains south through the western Transverse Ranges=20
should all get a healthy soaking today from the atmospheric river,=20
though since those areas have seen significantly less rainfall in=20
recent days compared to areas further north, have left most of these=20
areas in the Marginal.

Wegman

Day 2
Valid 12Z Wed Feb 05 2025 - 12Z Thu Feb 06 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF=20
THE OHIO VALLEY...

Strong southwesterly flow will advect abundant moisture northward
into the OH Valley on Wed into Wed night, with PWs forecast to
increase over the 90th percentile for early February. Increasing
WAA, a mid level shortwave moving east within the quick zonal=20
flow, and upper level divergence in the right entrance region of a=20
jet to the north and left exit region of a strong jet over the MS=20
Valley, will broadly support an expansion of showers across the=20
region. Model guidance continues to indicate upwards of 500-1000=20
j/kg near and south of a northward moving warm front, thus expect=20
we will see embedded thunderstorms as well. Given the forcing,=20
moisture and instability forecast, do anticipate we will see some=20
locally heavy rainfall rates materialize, especially by Wed evening
into the overnight near the lifting warm front.

Still some uncertainty on the location of this front, although
models are in much better agreement tonight compared to last=20
night. Precipitation north of the front will likely be either sleet
or freezing rain, and thus the position of this feature will be=20
important to delineate the northern edge of the flood risk area.=20
The current consensus for the axis of heaviest rainfall is across=20
portions of KY, southern IN/OH into much of WV. Some of these areas
may start as sleet/freezing rain, but will transition to locally=20
heavy rain as the warm front lifts north. Areal averaged rainfall=20
is currently forecast in the 0.5"-1" range, although given the=20
forecast instability, locally higher totals ~2" appear possible.=20
Portions of central/eastern KY into WV have above average soil=20
saturation and streamflows, and so this area is likely most=20
susceptible to some flooding impacts if higher rainfall rates do=20 materialize.

Chenard


Day 3
Valid 12Z Thu Feb 06 2025 - 12Z Fri Feb 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE OHIO VALLEY AND CALIFORNIA...

...OH Valley...
Another round of locally heavy rain is expected Thursday across
portions of KT/TN and WV along and ahead of an approaching cold
front. Locally heavy rainfall should be ongoing at 12z Thursday
across portions of WV, before a relative lull in activity by late=20
morning into the early afternoon. However by later in the afternoon
into the overnight hours another round of showers and embedded=20
thunderstorms should develop near the cold front over KY and=20
spread eastward into WV. Seeing enough instability forecast to=20
support locally heavy rainfall rates. Some of this corridor already
has above average soil saturation and streamflows, and there is=20
also some overlap between this day 3 rainfall and the day 2 rains.=20
Two day rainfall totals of 1-2" are forecast, but given the=20
instability both days, some areas could locally exceed 3". This=20
rainfall should be enough to result in at least some flooding=20
impacts.

...California...
After a one day break another system is forecast to move into CA=20
on Thursday. This is expected to be a pretty dynamic system, with a
strong mid level shortwave and upper level jet. These dynamics=20
should support a short duration period of enhanced rainfall=20
rates...although the quick forward motion of the system will limit=20
overall rainfall magnitudes. Not seeing much in the way of=20
instability currently forecast, and IVT and PWs are not overly=20
anomalous with this system either. These limitations will be=20
somewhat made up for by the stronger dynamics, however still not=20
expecting this to be a high end event. Rainfall totals around 1"=20
are forecast along coastal areas with 1-2" in the foothills of the=20
Sierra (snow levels will be lower with this system limiting=20
impacts). Given the saturated conditions over the region, this=20
quick shot of locally heavy rainfall may still be enough to=20
generate localized flood impacts, supporting the Marginal risk.

The Marginal risk extends southward into Santa Barbara, Ventura and
Los Angeles counties as well. Less rainfall forecast here, but
there is an uptick in IVT into the terrain, and so would not be=20
surprised if QPF trends up a bit as the event nears. Still not=20
expecting significant rainfall, but possibly enough for localized=20
impacts.

Chenard


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5txMahu3AfzUgV25E5rvNBQqug3vG8pvWy_khzJ5ehAC= jh7lODp0BdOqKA7-bAp1VG3na3A7yuvN-b6F76uGkIAwQ9M$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5txMahu3AfzUgV25E5rvNBQqug3vG8pvWy_khzJ5ehAC= jh7lODp0BdOqKA7-bAp1VG3na3A7yuvN-b6F76uGryeRJHw$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5txMahu3AfzUgV25E5rvNBQqug3vG8pvWy_khzJ5ehAC= jh7lODp0BdOqKA7-bAp1VG3na3A7yuvN-b6F76uGJlTw_ok$=20

=3D =3D =3D
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FOUS30 KWBC 060040
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
740 PM EST Wed Feb 5 2025

Day 1
Valid 01Z Thu Feb 06 2025 - 12Z Thu Feb 06 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OHIO VALLEY...

Only slight changes were made to the Marginal Risk area across the
Ohio Valley to account for radar reflectivity and 18z HREF
probabilities of 0.5"+ in an hour trends. Warm advection showers=20
are breaking out over KY & WV, and with increasing instability and
upper level divergence, will allow embedded convection to develop=20
into early Thursday morning. So far, hourly rain totals of 0.5-1"=20
have been estimated by radar in WV. Any thunderstorms which develop
and train will be capable of rainfall totals up to 1.5 inches in
an hour, with local amounts towards 3" anticipated. Soils in this=20
area remain nearly saturated and rivers are running high from the=20
rainfall event a few days ago. Thus, the additional rainfall=20
forecast tonight, even though amounts aren't expected to be overly
high, may cause isolated flash flooding.

Roth/Wegman


Day 2
Valid 12Z Thu Feb 06 2025 - 12Z Fri Feb 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE OHIO VALLEY AND CALIFORNIA...

...OH Valley...
Another round of locally heavy rain is expected Thursday across
portions of KY, TN, WV and far western VA along and ahead of an
approaching cold front. Showers and embedded thunderstorms will
likely be ongoing at 12z and may periodically continue through the
day/evening near the only slowly southward shifting front. While
nothing significant, CAPE upwards of 500-1000 j/kg still seems
likely along this corridor, which should be enough to support
locally heavy rainfall rates. While soil conditions and
streamflows are returning closer to average after the flooding
several days ago, some of this region is still likely more
sensitive than normal to additional heavy rainfall. The latest WPC
QPF is generally 0.75"-1", with two day totals locally exceeding
1.5". Given the instability forecast, it seems reasonable that we
will see isolated totals over 2". While the 00z GEM Reg and FV3LAM
are probably too high with totals, they both do suggest that if
convective coverage can increase enough then some 2-3" amounts can
not be ruled out. Overall expect this rainfall to pose a localized
flood risk.

...California...
After a one day break another system is forecast to move into CA
on Thursday. This is expected to be a pretty dynamic system, with a
strong mid level shortwave and upper level jet. These dynamics
should support a short duration period of enhanced rainfall
rates...although the quick forward motion of the system will limit
overall rainfall magnitudes. Recent model runs are showing some
uptick in rainfall amounts with this system over northern CA, but
still generally looking at totals in the 1-2" range. Given the
saturated conditions and brief potential for higher rates between
00z and 06z, this may be approaching Slight risk levels. Although
will hold off for now as the short duration of these higher rates
may limit the magnitude/coverage of impacts just enough to keep the
risk at Marginal.

The Marginal risk extends southward into Santa Barbara, Ventura and
Los Angeles counties as well. Less rainfall forecast here, but
there is an uptick in IVT into the terrain Thursday night, and PWs
do increase towards and just over 1". Larger scale forcing
generally shears off to the north, but the combination of
increasing PWs, IVT and upslope flow should be enough to result in
a period of moderate to locally heavy rain. We are beginning to
see a slow uptick in rainfall amounts in the models, and so
localized flood impacts are certainly a possibility. Although
given the overall weakening of the system and very little to no
instability, rainfall rates will probably only be high enough to
result in a minor flood risk over just the most sensitive urban
areas or recent burn scar locations.

Chenard

2100 UTC Update

No changes made to the previous marginal risk areas across CA or
from the Upper TN Valley into the Central Appalachians.

Oravec

Day 3
Valid 12Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Oravec


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!74im_G6ybqoEEgxZKJclbUv8CzIE4WPODlfcpSdZEMur= CY_RCGdPe6FUa0X9nK7_pNrFkJUMXwZRZXqCl4ydLKH5WR4$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!74im_G6ybqoEEgxZKJclbUv8CzIE4WPODlfcpSdZEMur= CY_RCGdPe6FUa0X9nK7_pNrFkJUMXwZRZXqCl4ydyTcGAoY$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!74im_G6ybqoEEgxZKJclbUv8CzIE4WPODlfcpSdZEMur= CY_RCGdPe6FUa0X9nK7_pNrFkJUMXwZRZXqCl4ydHVK9FW8$=20

=3D =3D =3D
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FOUS30 KWBC 062217
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
517 PM EST Thu Feb 6 2025

Day 1
Valid 2211Z Fri Feb 07 2025 - 12Z Fri Feb 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF CALIFORNIA AND THE OHIO VALLEY...

...California...
For a more detailed discussion please refer to Mesoscale=20
Precipitation Discussion (MPD) 23 that is valid until 03z this=20
evening.

After a one day break another system is forecast to move into CA=20
today and Thursday night. Not an AR but rather a compact, dynamic=20
system with a vigorous mid level shortwave and strong left exit=20
region upper level jet forcing. These dynamics should support a=20
short duration period of enhanced rainfall rates, although the=20
quick forward motion of the system will limit overall rainfall=20
magnitudes. Given the low-level ageostrophic response ahead of the=20
upper level jet streak, the latest (00Z) GEFS output shows a quick=20
uptick in southwesterly 850-700 mb moisture transport, peaking=20
between 3-4 standard deviations above normal across the central 2/3
of CA Thursday afternoon and evening. Recent model runs continue=20
to show 1-2+ inches falling mostly within 12 hours, with localized=20
amounts of 3+ inches over the coastal ranges and Sierra foothills=20
per the latest high-res guidance. Given the saturated conditions=20
and brief potential for higher rates (0.35+ in/hr) beginning around
21Z along the coast and by 00Z farther inland, this may result in=20
localized runoff issues, especially over burn scars across Santa=20
Barbara, Ventura, and Los Angeles counties.

Gallina/Hurley


...TN-OH Valleys into the Western Appalachians...
Another round of locally heavy rain has begun to occur across=20
portions of KY, TN, WV and far western VA- NC near and ahead of an
approaching cold front and near the base of a broad shortwave
transiting the Great Lakes. While precipitable water values are=20
run of the mill -- 0.75-1.25" -- the coolness of the atmosphere is
leading to significant saturation, which is aiding precipitation=20
efficiency. MU CAPE of 500-1000 J/Kg is being tapped by elevated=20
activity across west- central KY while similar values of ML CAPE=20
are being utilized by more surface based convection closer to the=20
front. The expectation given the above is for hourly rain totals to
1.5" and local amounts of 3" being possible, which is problematic=20
given the flash flood guidance values being depressed, roughly in=20
the 1-1.5" in 3 hour range. Some of this region is still likely=20
more sensitive than normal to additional heavy rainfall given the=20
1-3" that fell over the past 24 hours. Overall, a widely scattered=20
to scattered flash flood risk appears to exist. Mesoscale=20
Precipitation Discussion #24 covers the expectations through 04z=20
for portions of KY, northern TN, and southwest VA.

Roth/Hurley


Day 2
Valid 12Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Pereira


Day 3
Valid 12Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Pereira


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7QnxbMt0H_NWok-GLmEOXmy3OOThASpupQTgdH5xbsLy= c2gzNPxW6AhLJgbotuiE6_ewKjrAUDyVgAU7pA8AUFOtotc$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7QnxbMt0H_NWok-GLmEOXmy3OOThASpupQTgdH5xbsLy= c2gzNPxW6AhLJgbotuiE6_ewKjrAUDyVgAU7pA8AfSMVT_0$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7QnxbMt0H_NWok-GLmEOXmy3OOThASpupQTgdH5xbsLy= c2gzNPxW6AhLJgbotuiE6_ewKjrAUDyVgAU7pA8A4wZCO3w$=20

=3D =3D =3D
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FOUS30 KWBC 070735
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
235 AM EST Fri Feb 7 2025

Day 1
Valid 12Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 2
Valid 12Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 3
Valid 12Z Sun Feb 09 2025 - 12Z Mon Feb 10 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6gVZkpu8bi0e_zOHldMgY91D8vlrTi5R9UFw-btgC_Eq= zi3sYCBHVYbZ4on-leLtlG5vfEi-VlU_tB7GRlqxYgMUYWw$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6gVZkpu8bi0e_zOHldMgY91D8vlrTi5R9UFw-btgC_Eq= zi3sYCBHVYbZ4on-leLtlG5vfEi-VlU_tB7GRlqxpkyhlHU$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6gVZkpu8bi0e_zOHldMgY91D8vlrTi5R9UFw-btgC_Eq= zi3sYCBHVYbZ4on-leLtlG5vfEi-VlU_tB7GRlqxUqkULEU$=20

=3D =3D =3D
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FOUS30 KWBC 071613
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1113 AM EST Fri Feb 7 2025

Day 1
Valid 16Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Churchill/Hurley


Day 2
Valid 12Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 3
Valid 12Z Sun Feb 09 2025 - 12Z Mon Feb 10 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8NDGESHQ0CdgFb_X3HRsxVLIMDoLYNULdhzF33NphJbc= --Y6G0Z1uUT1DDezOTlgbz-DzVv9fYI43p3vgUunPEd3nrU$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8NDGESHQ0CdgFb_X3HRsxVLIMDoLYNULdhzF33NphJbc= --Y6G0Z1uUT1DDezOTlgbz-DzVv9fYI43p3vgUunnBILMYs$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8NDGESHQ0CdgFb_X3HRsxVLIMDoLYNULdhzF33NphJbc= --Y6G0Z1uUT1DDezOTlgbz-DzVv9fYI43p3vgUunKM-_l8E$=20

=3D =3D =3D
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FOUS30 KWBC 080733
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
233 AM EST Sat Feb 8 2025

Day 1
Valid 12Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025

...West Virginia...
Strong N-S quasi-zonal mid and upper level flow will be perturbed=20
a bit during Day 1 (12Z Sat-12Z Sun) as a 150+ kt upper level jet=20
streak traverses the Upper Midwest and Ohio Valley, while a flat=20
500 mb vort lobe pushes across the Lower Great Lakes. Broad-scale=20
exit region forcing associated with the upper jet axis will surge=20 southwesterly low-level inflow ahead of the surface frontal wave,=20
with 850 mb moisture flux anomalies peaking between 4-5 standard=20
deviations above normal later this afternoon into Sat night, while=20
TPW values peak around 1". Robust synoptic-scale support and low-=20
level moisture transport will be offset somewhat by the weak=20
elevated instability, with MUCAPEs generally less than 500 J/Kg.=20 Nevertheless, even though not advertised on the latest (00Z Sat)=20
HREF, the aforementioned dynamic and thermodynamic ingredients will
be sufficient for spotty hourly rain rates of 0.5"+ and 3-hourly=20
rates of 1.0"+, with localized event totals between 1.5-2.0"+.=20

Current 3-hr flash flood guidance values remain quite low (1" or
less) across the outlook area, which includes much of WV. Despite
the lack of instability, the low FFG values could be exceeded over
isolated areas with 2 consecutive hours of 0.5"+/hr rainfall rates.
Since the soils in these areas are saturated, and the terrain is=20
rugged, we have maintained the Marginal Risk area for much of WV=20
(outside of its northern or eastern Panhandles).

Hurley/Roth


Day 2 Valid 12Z Sun Feb 09 2025 - 12Z Mon Feb 10 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 3
Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Hurley


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7o8btsgTmcJHmJdtq43Nfsld0HaB6jQlg1atibjtptND= zXCWGvPIEVn8UQu1BNcf9TLo6E31wCqGgjv3reGGR-TqZHk$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7o8btsgTmcJHmJdtq43Nfsld0HaB6jQlg1atibjtptND= zXCWGvPIEVn8UQu1BNcf9TLo6E31wCqGgjv3reGGK_bvzy4$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7o8btsgTmcJHmJdtq43Nfsld0HaB6jQlg1atibjtptND= zXCWGvPIEVn8UQu1BNcf9TLo6E31wCqGgjv3reGGXXh2Hpc$=20

=3D =3D =3D
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FOUS30 KWBC 110836
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
336 AM EST Tue Feb 11 2025

Day 1
Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE
VALLEY...

Few changes needed to the old Day 2 ERO as it propagates into the
Day1 period. Main focus for heavy rainfall and the potential for
excessive rainfall will be along and ahead of a cold front
associated with a developing synoptic scale low pressure system
within a broad/fairly flat flow pattern. Inclusion of more CAM
guidance supports the idea of higher intensity rainfall extending=20
as far west as eastern Texas...a tendency we often see convection=20
get organized farther southwest than expected in events like this,=20
and there is growing QPF signal in the 12z ECMWF, UKMET and Gem Reg
over this area. The Slight risk area extended northeastward where=20
there is a bit of instability that develops later in the period but
looks to be lacking initially. At expect the flash flood risk to=20
pick up more over this area as we head into day 2.

Bann

Day 2
Valid 12Z Wed Feb 12 2025 - 12Z Thu Feb 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
TENNESSEE VALLEY INTO THE MID-SOUTH...

...Tennessee Valley into the Mid-South...

The prolonged heavy rainfall event will continue om Wednesday into
Wednesday night over the Southeast. The extended duration of this=20
event will lead to storm total rainfall into the 3-5" range, with=20
locally higher totals possible. As stronger forcing ejects eastward
on Wednesday, an increase in the low level jet should aid in both=20
increasing moisture convergence and advecting instability
northward. The best overlap of ingredients that has the potential
for excessive rainfall looks to be over parts of AL/GA into far
southwest Tennessee. This is approximately the same area as the
previous Day 3 outlook...and given no major shifts in the synoptic
pattern saw little reason to make too many changes.

...California Coast...
The plume of moisture from the Pacific Ocean towards the end of Day
2 will start to bring rain to the coastal areas during the Day 3 period...beginning in northern and central portions of California
on Wednesday that propagates southward on Wednesday night and=20
early Thursday. Present indications are that the axis of the
Atmospheric River and the associated heaviest amounts remain off=20
shore or right along the coastal terrain...but a general uptick in
amounts was noted over the past 24 hours in this area.

Bann


Day 3
Valid 12Z Thu Feb 13 2025 - 12Z Fri Feb 14 2025

..THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL PARTS OF THE=20
SOUTHERN CALIFORNIA COAST...

There is a Moderate Risk of excessive rainfall over portions of the
Southern California coast embedded within a broader Slight risk of
excessive rainfall covering much of the central and southern=20
California coast. An atmospheric river is expected to skirt the=20
coast as it makes its way south and east. The primary concern is
for damaging flooding and debris flow from the numerous fresh burn
scars in the region given the 24-hour QPF in the 1.5 to 3.5 inch=20 range...with potentially localized higher amounts. In=20
addition...the area is highly urbanized and an environment in which
much of the rainfall will turn immediately to runoff. Farther=20
north...the Slight risk was extended into portions of the=20
Sacramento Valley and San Joaquin Valley...where QPF is not=20
expected to be as great but the conditions have been wetter and=20
soils are more saturated than soils farther south.

Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!52MPZ4O1I7Nlf3uDL1Xme9BfrDRTPJJJhspfHzdT7Hwi= rMJrOr2hctDur3jXAOfRz1pc6uTOXu-n5ILOlbgiujxkUx0$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!52MPZ4O1I7Nlf3uDL1Xme9BfrDRTPJJJhspfHzdT7Hwi= rMJrOr2hctDur3jXAOfRz1pc6uTOXu-n5ILOlbgivU9XJaE$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!52MPZ4O1I7Nlf3uDL1Xme9BfrDRTPJJJhspfHzdT7Hwi= rMJrOr2hctDur3jXAOfRz1pc6uTOXu-n5ILOlbgiIQv6szE$=20

=3D =3D =3D
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FOUS30 KWBC 130812
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
312 AM EST Thu Feb 13 2025

Day 1
Valid 12Z Thu Feb 13 2025 - 12Z Fri Feb 14 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF SOUTHERN CALIFORNIA...

...California...
Overall, not much change to the previous forecast, with the=20
unfolding atmospheric river expected to peak near the start of the=20
period. A long warm front currently extending along the coast is=20
expected to press inland this morning, with IVTs climbing to around=20
700-800 kg/m/s near the upstream cold front as it approaches the=20
coast later this morning. The strongest moisture flux is expected=20
to center near SF Bay at the start of the period, before steadily=20
shifting south along the coast today. Models continue to show IVTs=20 decreasing as the axis moves south, dropping to around 400-500=20
kg/m/s as the AR reaches Southern California later this afternoon=20
into the evening. Guidance has remained fairly consistent,=20
indicating precipitation amounts of 4-6 inches along the central to
southern coastal ranges and the Sierra Nevada, falling mostly as=20
rain below 6000 ft.=20

A Moderate Risk (level 3/4) remains in place across portions=20
Southern California, from Santa Barbara County southeastward into=20
the San Gabriel and San Bernadino mountains, where damaging and=20
potentially life-threatening burn scar flash flooding and debris=20
flows remain a primary concern. Even outside of the burn scar areas,=20
intense rain rates over complex terrain and urban areas may produce=20 scattered to numerous instances of flash flooding. Elsewhere, a=20
broad Slight Risk (Level 2/4) exists for much of the remaining=20
coastal ranges as well as parts of the Central Valley and the lower
elevations of the Sierra Nevada.=20

...Florida Panhandle and Southern Georgia...=20

Lingering heavy rainfall will continue this morning across=20
portions of the Florida Panhandle and southern Georgia ahead of an=20 approaching cold front. HREF neighborhood probabilities indicate=20
that additional rainfall amounts of 1-2 inches are likely within=20
the highlighted area, with some potential for localized rain rates=20
high enough to cause some urban/localized flooding concerns.

Pereira


Day 2=20
Valid 12Z Fri Feb 14 2025 - 12Z Sat Feb 15 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MID-SOUTH...

...Mid-South...=20

Although most of the convective activity, and thus heavy rainfall=20
threat, in the region should be concentrated in the Day 3 period=20
(after 12Z Saturday), model guidance does indicate that convection=20
is likely to begin blossoming late Friday Night. Conditions will=20
become increasingly favorable after 06Z Saturday with a strong 55-65=20
knot low-level jet expanding east from the Plains, and significant=20
northward moisture transport leading to rapid moistening of the=20
boundary layer. MUCAPE values of around 500-1000 j/kg should support=20 organized convection with the potential for rainfall rates in excess=20
of 1 inch per hour at times. Although there is a lack of a=20
significant front or boundary to help organize a band of convection,=20
the strength of the LLJ may support backbuilding within a broad zone=20
of developing convective clusters. This may be enough for some brief=20 training and a ramp-up in flash flood potential prior to 12Z=20
Saturday. The 00Z runs of the NAM Nest and FV3 show more widespread=20 convection than other models; if this trend persists as additional=20
hi-res guidance becomes available, an expansion of the Marginal Risk=20
and/or the addition of a Slight Risk area may become warranted with=20
time.

...Southern California...=20

The Marginal Risk was removed for southern California given a more
limited QPF signal on the latest guidance, and hi-res models in=20
excellent agreement on a lack of organized convection. The bulk of=20
the threat should be in the Day 1 period.

Lamers

Day 3
Valid 12Z Sat Feb 15 2025 - 12Z Sun Feb 16 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE TENNESSEE AND OHIO VALLEYS AND THE CENTRAL APPALACHIANS...

...Ohio and Tennessee Valleys...

Confidence remains high in significant rainfall-related impacts on=20
Saturday and Saturday Night with model guidance in excellent=20
agreement depicting a swath of 3-6 inches of rainfall in the 24-hour=20
period across the region. Although models vary slightly with the=20
placement, they almost unanimously depict a corridor of heavy rain=20
about 750mi long centered somewhere in TN/KY. This same region has=20
generally seen above average precipitation in recent weeks, with the=20
14-day precip in much of KY, N TN, WV, and W VA at least double the=20
normal values. The confluence of these factors should make the=20
region especially vulnerable to flooding from the predicted=20
rainfall. For additional context on the current hydrologic picture=20
across the region, refer to the National Hydrologic Discussion from=20
the National Water Center at water.noaa.gov.

Convection may be ongoing at the beginning of the forecast period=20
and should become increasingly focused along a developing warm front=20
to the east of a surface low that will be emerging out of the Plains=20
on Saturday. The front will be positioned on the nose of very strong=20
SW, or even WSW, inflow, which should favor backbuilding and=20
training and a corridor of very heavy rainfall. The environment will=20
be atypical of mid-February with PWATs reaching around 1.5 inches=20
and MUCAPE of 500-1000 j/kg. For example, the Nashville sounding=20
archive exists back to 1948 and they've only ever reached 1000 j/kg=20
MUCAPE once in February, and 1.5 inch PWATs a few times. The=20
environment will support rainfall rates in excess of 1 inch per=20
hour, and given the potential for training and backbuilding, these=20
rates may be sustained for several hours in some locations. These=20
would be the areas of greatest concern for flash flooding -- not=20
only in terms of likelihood but severity -- particularly if the=20
higher rain rates are sustained over urban areas or vulnerable=20
terrain for extended periods of time.

The inherited Moderate Risk was mostly maintained as-is with a=20
slight expansion to the southwest in the vicinity of Memphis, TN;=20
and a more significant expansion eastward into S WV and W VA. The WV-
VA border region just received some significant snowfall, and model=20
guidance indicates a fairly high probability of warm, moist air (dew=20
points in excess of 45 degrees) accompanying the rainfall into this=20
area, which may lead to a combination of runoff from rain and snow=20
melt.

It's worth noting a couple additional things. First, the amount of=20
rain forecast from E KY into S WV and W VA in particular is quite=20
unusual for the heart of the winter season. Calendar day precip=20
records across that area for January and February are generally in=20
the 2-3 inch range, and NBM probabilities indicate it is likely (60+=20
percent chance) we will see these types of 24-hour rainfall totals=20
in those areas. Second, this relatively rare winter rain event would=20
be delivered to an area that has been quite wet recently, and in=20
some areas has snow on the ground. And third, the high-end scenarios=20
in much of the Moderate Risk area would be significant by historical=20 standards. The NBM 90th percentile from N TN into S/E KY and S WV is=20
on par with the top several wettest days (for any season!) in the=20
station records in the area. This corridor is where the greatest=20
concern for severe impacts exists, and it's possible an upgrade to=20
High Risk may be needed for portions of the area in subsequent=20
updates.

Lamers

Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_P91ui_wceXaBtbPdzDS2U2ejXAZ4l7JBKrHAppXy2j3= n75PhydOMS61ECXA_hSACD86zA71nmYnj-U9fKdlvg7HAHc$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_P91ui_wceXaBtbPdzDS2U2ejXAZ4l7JBKrHAppXy2j3= n75PhydOMS61ECXA_hSACD86zA71nmYnj-U9fKdl9tWZdKc$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_P91ui_wceXaBtbPdzDS2U2ejXAZ4l7JBKrHAppXy2j3= n75PhydOMS61ECXA_hSACD86zA71nmYnj-U9fKdlXXvtJd8$=20

=3D =3D =3D
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