Storm Prediction Center Mesoscale Discussion 927

   Mesoscale Discussion 0927
   NWS Storm Prediction Center Norman OK
   0915 PM CDT Sun May 31 2026

   Areas affected...Far southeast South Dakota into adjacent portions
   of Nebraska and Iowa

   Concerning...Severe Thunderstorm Watch 257...

   Valid 010215Z - 010415Z

   The severe weather threat for Severe Thunderstorm Watch 257
   continues.

   SUMMARY...A localized corridor of higher tornado potential may
   persist for the next couple of hours across far southeast South
   Dakota into adjacent portions of Iowa and Nebraska.

   DISCUSSION...Additional tornadic supercells have emerged immediately
   west of the Sioux Falls, SD and the I-29 corridor based on radar
   imagery from KFSD. Near-storm 0-1 km SRH sampled by the local VWP
   has recently increased to around 200 m2/s2 immediately ahead of the
   approaching storms. Consequently, the near-storm environment is more
   favorable for tornadoes than previously anticipated, though storm
   interactions appear to be modulating the duration of the tornado
   threat to some degree. Additional supercell development is noted on
   the southern flank of the emerging cluster, and is already showing
   signs of an organizing low-level mesocyclone. It appears likely that
   some tornado threat will likely continue for the next 1-2 hours -
   most likely on the southern flank of the cluster as it migrates
   east/southeast into far northeast NE/northwest IA. Based on the
   near-storm environment and observed velocity signatures, a strong
   tornado appears possible.

   ..Moore.. 06/01/2026

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

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

   LAT...LON   42589728 43109709 43329697 43359662 43289611 43139602
               42919595 42689607 42519629 42459661 42489704 42589728 

   MOST PROBABLE PEAK TORNADO INTENSITY...100-125 MPH
   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN