Storm Prediction Center Mesoscale Discussion 1942

   Mesoscale Discussion 1942
   NWS Storm Prediction Center Norman OK
   1000 PM CDT Tue Aug 11 2026

   Areas affected...Parts of western into south-central SD and far
   northern NE

   Concerning...Severe Thunderstorm Watch 569...

   Valid 120300Z - 120430Z

   The severe weather threat for Severe Thunderstorm Watch 569
   continues.

   SUMMARY...A severe wind and hail risk may continue tonight into
   south-central South Dakota and vicinity, with downstream watch
   issuance possible.

   DISCUSSION...A well established supercell has gradually transitioned
   into a small bowing complex across western SD over the past hour or
   two, with mainly measured severe wind gusts up to around 75-80 mph.
   Even with the onset of nocturnal cooling, a reservoir of rich
   low-level moisture (with upper 60s to low 70s surface dewpoints) and
   steep mid-level lapse rates are supporting a narrow corridor of
   strong instability per latest mesoanalysis estimates. It is
   plausible that the ongoing small bow will track east-southeastward
   along the instability axis into south-central SD over the next few
   hours while continuing to pose a threat for severe gusts and hail.
   Time-lagged HRRR/RRFS runs support this scenario, with some members
   showing significant gust potential (75+ mph) persisting with
   eastward extent. Therefore, downstream watch issuance is being
   considered for parts of southern SD and far northern NE before the
   04Z expiration of Severe Thunderstorm Watch 569.

   ..Gleason/Mosier.. 08/12/2026

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

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

   LAT...LON   44090277 44620168 44400022 44149883 43639818 42909843
               42819932 42880113 43230277 43960281 44090277 

   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