ACUS11 KWNS 132011
SWOMCD
SPC MCD 132011=20
SDZ000-WYZ000-132145-

Mesoscale Discussion 1939
NWS Storm Prediction Center Norman OK
0311 PM CDT Wed Aug 13 2025

Areas affected...portions of northeastern Wyoming into western South
Dakota

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

Valid 132011Z - 132145Z

Probability of Watch Issuance...60 percent

SUMMARY...The severe threat is increasing across portions of the
northern Plains. Severe wind and hail are the main threats, with an
organized wind threat likely if storms merge into an MCS.

DISCUSSION...A multicellular cluster has developed across northern
WY, and is gradually intensifying (based on increasing lightning
trends) as a mid-level vort max traverses the northern Rockies. As
such, the ongoing convection should persist as it progresses into SD
over the next few hours. With the approach of the vort max,
deep-layer shear should continue to strengthen, with widespread 40
kts of effective bulk shear likely. At the same time, MLCINH will
continue to erode as surface temperatures climb into the 90s F amid
upper 50s F dewpoints in western SD, boosting MLCAPE to 1000 J/kg.=20

The combination of this buoyancy and mainly elongated hodographs
will encourage continued multicellular development and perhaps
preceding supercells, accompanied by both a severe wind and hail
threat. With time though, upscale growth into an MCS is possible,
particularly in western SD. This MCS will then approach a more moist
low-level airmass while traversing a surface boundary, with surface
dewpoints well into the 60s F, which will encourage further
strengthening and associated potential for some wind swath
organization. As such, a Severe Thunderstorm Watch will eventually
be needed, with timing of watch issuance remaining the primary
question.

..Squitieri/Mosier.. 08/13/2025

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!8BObzG_VHVdhPCHmCGgdOfhmfDRP_xr5VRzbTLXtRSJOI4oapNSvTJlkW9Oqmfnl4-RZmiGQA= P4dgCyXFO2IN5QktQw$ for graphic product...

ATTN...WFO...ABR...UNR...CYS...

LAT...LON 43370479 43720523 44130546 44500554 44760552 44900540
44900353 44640094 44339997 43859975 43469988 43190048
43090141 43090226 43080304 43210406 43370479=20

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN




=3D =3D =3D
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