Storm Prediction Center Mesoscale Discussion 2190

   Mesoscale Discussion 2190
   NWS Storm Prediction Center Norman OK
   0626 PM CDT Tue Sep 01 2026

   Areas affected...southeast SD and northeast NE

   Concerning...Severe Thunderstorm Watch 639...

   Valid 012326Z - 020130Z

   The severe weather threat for Severe Thunderstorm Watch 639
   continues.

   SUMMARY...Large hail greater than 2 inch diameter and severe wind
   gusts remain possible across Severe Thunderstorm Watch 639.
   Clustering/upscale growth could increase damaging wind potential
   over the next couple of hours.

   DISCUSSION...Isolated supercell storms have produce very large hail
   and severe wind gusts over the past 1-2 hours near the SD/NE border
   within Severe Thunderstorm Watch 639. Continued thunderstorm
   development along a low-level convergence zone is resulting in
   clustering this evening as convective mode becomes somewhat messier
   via storm interactions. Storms that can remain more discrete will
   likely remain supercells capable of producing very large hail and
   severe wind gusts. If sufficient clustering and consolidation of
   outflows occurs, a forward propagating bow or small MCS may develop
   in the next couple of hours on the northwest periphery of an
   developing southwesterly low-level jet across the Mid-MO Valley. If
   this occurs, damaging wind potential could increase across parts of
   southeast SD/northeast NE over the next couple of hours.

   ..Leitman.. 09/01/2026

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

   ATTN...WFO...FSD...OAX...LBF...

   LAT...LON   43459907 43789715 43689652 43289637 42719644 42299769
               42059926 42189969 42649965 43309936 43459907 

   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