ACUS11 KWNS 162252
SWOMCD
SPC MCD 162252=20
SDZ000-MTZ000-WYZ000-170045-

Mesoscale Discussion 1317
NWS Storm Prediction Center Norman OK
0552 PM CDT Mon Jun 16 2025

Areas affected...south-central/southeast Montana...east
Wyoming...and far west South Dakota

Concerning...Severe potential...Watch possible=20

Valid 162252Z - 170045Z

Probability of Watch Issuance...40 percent

SUMMARY...Thunderstorms will continue to increase in coverage this
evening. Isolated large hail and damaging winds will be possible
with the strongest thunderstorms. A watch may be needed.

DISCUSSION...Thunderstorms are developing this afternoon across the
higher terrain across south-central Montana. These thunderstorms
have a history of producing severe hail as they move east-southeast.
Strong effective-shear on the order of 40-50 knots and most-unstable
CAPE around 1500 J/kg should support a continued threat for at least
sporadic severe hail.

To the south, additional thunderstorms have developed across the
higher terrain of central Wyoming and farther south in southeast
Wyoming. The environment is more favorable for severe hail/wind here
than farther to the northwest, with effective-layer shear generally
at or above 50 knots and most-unstable CAPE on the order of
2000-3000 J/kg. A recent storm/cluster of storms on the
Converse-Albany county line has rapidly intensity with MESH values
in the 1-1.5 inch range. Additional thunderstorm development is
expected this afternoon/evening.

The expected evolution of these two clusters is to eventually merge
together across northeast Wyoming and push into western South Dakota
later this evening. Buoyancy across South Dakota looks weaker than
areas farther west and a general decrease in thunderstorm intensity
is expected through the loss of diurnal heating and movement into a
slightly more stable environment.=20

Current expectation is that a watch may be needed given the overall environment. However, uncertainty remains as to the potential
coverage of severe threat along with the eventually evolution/merger
of these two areas. Trends will continue to be monitored for
potential watch issuance.

..Marsh/Mosier.. 06/16/2025

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!6r-NCOP4NC-aoyVZrL3wXTwI2JwIdXHq51Gu1ocCpeUXuqNYRC-9mEESumiHPAtuGdWx8Z9lu= NyfAcB_TzF2Ffu0yVM$ for graphic product...

ATTN...WFO...UNR...CYS...BYZ...GGW...RIW...TFX...

LAT...LON 42260648 43230880 45341102 46701028 47050800 46450557
45080320 43570346 43020430 42230443 42140600 42260648=20

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN


=3D =3D =3D
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