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QPFERD

Excessive Rainfall Discussion...UPDATED
NWS Weather Prediction Center College Park MD
424 PM EDT Thu Jun 4 2026

Day 1
Valid 16Z Thu Jun 04 2026 - 12Z Fri Jun 05 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER A PORTION OF
THE UPPER MIDWEST...

...16Z Outlook Update...
The ongoing outlook is generally on track. The Slight Risk area was
expanded slightly south/southwestward across northeastern Kansas to
account for latest trends in CAMs that suggest potential for
convective training and prolonged rainfall generally along the
I-70 corridor from Salina to Topeka and vicinity late
today/tonight. Otherwise, one or more complexes of storms are
expected to traverse the Slight Risk area from northeastern Kansas
into Iowa from afternoon through the overnight hours, with
localized training and convective mergers expected to produce
isolated to scattered instances of flash flooding.

Elsewhere, scattered, slow-moving convection will likely result in
isolated flash flood instances especially from New Mexico/southwest
Texas thorugh southeast Texas and soutwestern Louisiana. Another
complex of storms should migrate eastward across South Dakota today
and prompt localized training/flash flood concerns across
eastern/northeastern portions of that state. Isolated/urban flash
flooding is possible across southeastern Florida as well.

See the previous discussion below for more information.

Cook

...Previous Discussion...

Circulation around a broad area of high pressure over the
Northeast US and the Mid-Atlantic Region will keep an easterly flow
of deep moisture over Florida and and anticyclonic flow from the
Texas and Louisiana Gulf coast that becomes southwesterly from
parts of the Central Plains/Upper Midwest through much of the
period. An upper low over northern Mexico will help draw some of
that moisture westward to support the risk of locally heavy
rainfall there.

...Gulf Coast to Upper Midwest/Northern Plains...
With a persistent fetch of an airmass from the Gulf Coast region
into the Upper Midwest...precipitable water values increase
throughout the day...exceeding 2 inches along the Texas Gulf coast
to the ARKLATEX while increasing to 1.5 inches or more in a plume
extending into parts of Minnesota and Wisconsin. The highest
probability of heaviest rain was shown in both the operational
models and the ensembles across parts of Iowa into portions of
nearby Nebraska and Kansas as mid level height falls make their way
out of the High Plains and as surface pressures fall. Rainfall
rates of 1-2 inches per hour are possible. The 00Z runs of the HREF
and the RRFS show neighborhood probabilities of 10 to 20 percent
occurrence for 2 inch amounts in 3 hours for the 24 hour period
ending at 12Z Friday morning. Those rates could be enough to
overcome initially dry soils in parts of the area as well as be
problematic in urban areas.

Elsewhere along that corridor...there is sufficient CAPE to drive
locally intense downpours from any convection that forms. The big
problem is the relatively weak shortwave energy within the flow
will be difficult to time with much lead-time. As such...left the
Marginal Risk area pretty much in place with the expectation that
some area may well stay rain-free.

...West Texas to Eastern New Mexico...

An upper level system over Mexico will help draw some of the deeper
Gulf moisture westward...keeping a risk of locally heavy rainfall
and isolated instances of flash flooding. As previously
mentioned...the overall organization of the convection is expected
to be on the lower side, but the precipitable water anomalies and
the subtle increase in the upper level difluence near the
international border support potential for locally intense rain
rates and the Marginal Risk.

...South Florida...
Frontal boundary stalling in the vicinity of the area will remain
the focus for scattered to numerous showers and thunderstorms
capable of producing intense rain rates and locally heavy rainfall
over the highly urbanized corridor. The risk shifts a bit farther
south across South Florida compared with yesterday...mainly
centering across the Miami metro.

Bann

Day 2
Valid 12Z Fri Jun 05 2026 - 12Z Sat Jun 06 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
EASTERN NEBRASKA INTO THE MID-MISSISSIPPI VALLEY...

...21Z Outlook Update...

The Slight Risk in the previous D2 issuance has been shifted
southwestward and expanded slightly based on most recent model
trends. Fairly progressive convection should migrate across much of
Wisconsin and Lower Michigan in the morning/early afternoon hours.
During the latter parts of the forecast period (afternoon onward),
Additional, surface-based convection should redevelop near the
NE/IA border and migrate eastward toward the MS River/IA/IL border
region. This convection should be oriented favorably for local training/backbuilding - and some of that convection (particularly
in Iowa) could fall on wet soils from prior-day anticipated
rainfall, creating more moist ground conditions favoring excessive
runoff. The current configuration of Slight reflects most recent
model depictions of heavy rainfall risk from deep convection.

Elsewhere, the overall forecast is generally on track, with small
spatial expansions of Marginal in New Mexico to account for
potential convection in higher terrain. Scattered thunderstorms
should move slowly across the entire Marginal Risk area from
NM/west Texas eastward to southeast Texas. Some consideration of
Slight was given for the Big Country/Hill Country with a nearly
stationary mid/upper trough upstream and copious moisture content
present. Instability and convective coverage were in question
though and will likely be dependent on prior-day convection and the
evolution of any potential complexes from west Texas that migrate
through the region during the early morning hours. After collab
with local WFOs, decision was made to wait another model cycle
before reconsideration of a potential upgrade.

Though specific timing is uncertain, a disturbance over the central
Gulf will begin to migrate slowly northwestward toward southeastern
Louisiana and pose heavy rainfall potential across that area and
adjacent areas of Mississippi. Wet soils from prior rainfall will
support excessive runoff should heavier rainfall/deep convection
materialize as suggested by models.

Cook

...Previous Discussion...

Upper Midwest...
Additional scattered thunderstorm activity is expected once again
ahead of a front making its way from Iowa into Wisconsin and
vicinity, spreading 1-2 inches of rain with local amounts reaching
4 inches. Storms in that area should be progressive in nature due
to 20-30 knot mid/upper level flow, though localized backbuilding
and mergers may increase totals locally.

The Marginal Risk surrounding the Slight Risk was largely
unchanged...although some of the territory was removed from the
northern part of Michigan now that timing of the boundary and low
level moisture fields have become handled better by the
models/ensembles.

Texas into New Mexico...
Weak mid/upper troughing across the southern Rockies and Texas
will promote another round of thunderstorm activity across a large
part of Texas and southern New Mexico, with attendant flash
flooding expected due to slow storm motions and abundant moisture.

Coastal Louisiana...
A trough of low pressure interacting with the higher moisture in
place will bring a higher coverage of thunderstorms with the
potential for intense rain rates and localized heavy rainfall.
Spaghetti plots show more ARW core members than NMMB...suggesting
that there could still be shifts in placement or QPF amounts
between now and the time the outlook verifies.

Bann

Day 3
Valid 12Z Sat Jun 06 2026 - 12Z Sun Jun 07 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE GREAT LAKES/OHIO VALLEY AND ACROSS THE MIDDLE GULF COAST INTO
THE SOUTHERN PLAINS...

...21Z Outlook Update...

The overall forecast is on track with minimal changes made based on
latest model trends. The Slight Risk along the Upper Ohio Valley
westward to Illinois was expanded/shifted southward and westward to
account for latest model trends, which develop scattered
thunderstorm activity (likely in the form of clusters/linear
segments) across the discussion area during the afternoon and
evening. Guidance has shifted somewhat more south with precip
maxima into northern West Virginia, with more isolated thunderstorm
activity expected with westward extent into Illinois. Isolated
instances of flash flooding appear possible in this regime.

Across Texas and Oklahoma, a persistent mid-level trough will
likely continue to spawn scattered to numerous shower/thunderstorm
activity, with latest guidance depicting QPF maxima near the Red
River and into western north Texas. Much of this evolution will
depend on development and persistence of any complexes from prior-
day convection, which lends uncertainty at this timeframe. Should
trends hold, a Slight may be needed in portions of west Texas and
the Big Country.

Lastly, models are in general agreement that a Gulf disturbance
will reach land over southeastern Louisiana and spread areas of
heavy rainfall over Louisiana and Mississippi. Local convective training/banding may be possible depending on the organization of
the disturbance. Current trends suggest additional heavy rainfall
potential over wet/sensitive ground conditions from prior rainfall
in the area the past couple weeks. Flash flooding is possible on at
least an isolated basis.

See the previous discussion below for more information.

Cook

...Previous Discussion...

Great Lakes/Ohio Valley... Maintained a
Marginal Risk area over portions of Ohio Valley and nearby southern
Great Lakes as a front become oriented along an east to west axis
and flow aloft is weakly forced to lift isentropically. Maximum
areal average rainfall after the start of the period at 12Z
Saturday generally looks to be little more than an inch. The
cumulative effect of rainfall on Days 2 and 3 suggested it was too
early to entirely remove the Marginal.

Texas northward into the Southern Plains...
Little change in the overall synoptic pattern is expected with
southerly flow of moisture continuing to be drawn into parts of the
Southern Plains. Some stronger/better defined shortwave energy
within the flow aloft will promote yet another round of
thunderstorm activity across a large part of Texas and southern New
Mexico and extending as far north as parts of Oklahoma/Arkansas and
Kansas by late Saturday night/early Sunday morning, with attendant
flash flooding expected due to slow storm motions and abundant
moisture.


Bann


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4RMtMHdY5TaFNuvf8C1_76R5WmMOWM409dmbVmglp40V= zwd54R1TI3S27ixjzaFUwMJHRC73Oc4EP498TNBQoWYtHIA$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4RMtMHdY5TaFNuvf8C1_76R5WmMOWM409dmbVmglp40V= zwd54R1TI3S27ixjzaFUwMJHRC73Oc4EP498TNBQ0FHKaq0$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4RMtMHdY5TaFNuvf8C1_76R5WmMOWM409dmbVmglp40V= zwd54R1TI3S27ixjzaFUwMJHRC73Oc4EP498TNBQYaBd-6U$=20

=3D =3D =3D
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