Subj : MESO: Mesoscale Discussion 1971
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Aug 17 2025 07:48:23

ACUS11 KWNS 170748
SWOMCD
SPC MCD 170747=20
SDZ000-NDZ000-170915-

Mesoscale Discussion 1971
NWS Storm Prediction Center Norman OK
0247 AM CDT Sun Aug 17 2025

Areas affected...Northwest/north-central SD into
southwest/south-central ND

Concerning...Severe Thunderstorm Watch 597...

Valid 170747Z - 170915Z

The severe weather threat for Severe Thunderstorm Watch 597
continues.

SUMMARY...An increase in the severe-wind threat remains possible
overnight.

DISCUSSION...A storm cluster over western SD has shown signs of
becoming better organized over the last 30-60 minutes, with
indications of bow-echo development across northwest SD, and recent
observed wind gusts of 50-60 mph. MUCAPE remains in the 2500-4000
J/kg range, due to steep midlevel lapse rates atop a richly moist
boundary layer (as observed in the 00Z UNR sounding). Meanwhile,
backed low-level flow beneath modest southwesterlies aloft is
supporting effective shear of 25-35 kt, sufficient for organized
convection.=20

A modest nocturnal low-level jet combined with the favorable
instability and deep-layer shear will support continued
intensification of the ongoing cluster, and maintenance of this
cluster through much of the overnight hours. Short-term guidance
suggests that this developing MCS will generally move northeastward
along the MUCAPE and low-level moisture gradient. The magnitude of
the wind threat remains somewhat uncertain, due to the presence of
low-level stability and surface-based CINH. However, if an organized
MCS does persist, some increase in severe-wind potential is expected
overnight from northern SD into southern ND.

...Dean.. 08/17/2025

....Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj=
g!_rYcV0fFATylJzsY0UOdskVCCwkZcGQ2Qlkq6bDVvFW7Z7TadAm9abE_4FdqJpolN3C9bPEhz=
lFg9HwrDcNGnSLEq8E$  for graphic product...

ATTN...WFO...ABR...BIS...UNR...

LAT...LON   45690234 46320209 46540110 46709979 45869933 45339923
            44759944 44280019 44370204 45240186 45690234=20

MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN


=3D =3D =3D
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