Storm Prediction Center Mesoscale Discussion 2109

   Mesoscale Discussion 2109
   NWS Storm Prediction Center Norman OK
   0813 PM CDT Sun Aug 23 2026

   Areas affected...Parts of northwestern South Dakota

   Concerning...Severe Thunderstorm Watch 618...

   Valid 240113Z - 240245Z

   The severe weather threat for Severe Thunderstorm Watch 618
   continues.

   SUMMARY...The risk of large hail and severe wind gusts should
   generally remain confined to parts of northwestern South Dakota in
   Severe Thunderstorm Watch 618.

   DISCUSSION...A discrete right-moving supercell (and upstream cell
   development) is tracking southward across far northwestern SD, with
   recent reports of large hail and a severe wind gust. In the near
   term, this activity will continue moving southward through a
   corridor of weak-moderate surface-based buoyancy and around 40 kt of
   effective shear. This environment will continue to support discrete
   supercells with a risk of large to very large hail and severe wind
   gusts. Eventually, these storms will move into an area of increasing
   low-level inhibition (sampled by the UNR 00Z sounding), which should
   limit the severe risk with southward extent.

   ..Weinman.. 08/24/2026

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

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

   LAT...LON   44620332 45390353 45660347 45880335 45950291 45920248
               45560218 44940197 44560222 44450295 44620332 

   MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
   MOST PROBABLE PEAK WIND GUST...65-80 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN