Storm Prediction Center Mesoscale Discussion 1940

   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