792
ACUS11 KWNS 132221
SWOMCD
SPC MCD 132221
SDZ000-NEZ000-140015-

Mesoscale Discussion 1940
NWS Storm Prediction Center Norman OK
0521 PM CDT Wed Aug 13 2025

Areas affected...Southern South Dakota

Concerning...Severe Thunderstorm Watch 588...

Valid 132221Z - 140015Z

The severe weather threat for Severe Thunderstorm Watch 588
continues.

SUMMARY...The threat for severe winds, and possibly hail, is
increasing across southern South Dakota.

DISCUSSION...Latest lightning data shows a steady uptick in
intensity of a developing MCS across western SD with multiple severe
wind gusts between 55-70 mph noted across far northeast WY and far
western SD. This system is beginning to impinge on richer
boundary-layer moisture in place across SD, which improves further
with eastward extent. Additionally, latest upper-air analyses show a
plume of steeper mid-level lapse rates extending eastward downstream
of the MCS, which will also help maintain intensity. Recent velocity
data from KUDX shows 60-70 mph winds within the lowest kilometer,
which will likely manifest at the surface given steep lapse rates
within this layer. With further intensification possible, gusts
upwards of 80 mph appear possible.

Further east, surface pressure falls and increasing low-level
convergence is noted in surface observations near Pierre, SD with a
few attempts at deep convection noted in GOES imagery and lightning
data. This area of ascent may be the initiation zone for discrete
cells over the next couple of hours, which may intensify as they
move east into a plume of higher theta-e air where MLCAPE is around
2000 J/kg. RAP mesoanalyses also suggest low-level SRH and effective
shear is adequate for supercells that may pose a threat for large
hail and perhaps a brief tornado. Confidence in this scenario is
limited, but environmental conditions suggest a supercell or two is
plausible in the coming hours.

..Moore.. 08/13/2025

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...FSD...ABR...LBF...UNR...CYS...

LAT...LON   42890239 42940268 43010287 43140313 43240332 43460365
            43730388 44090389 44580394 44820383 45030362 45110338
            44519930 44289891 43949859 43379837 43159844 42909867
            42839893 42819940 42890239

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN