Storm Prediction Center Mesoscale Discussion 1358

   Mesoscale Discussion 1358
   NWS Storm Prediction Center Norman OK
   0710 PM CDT Sat Jun 27 2026

   Areas affected...portions of southwestern South Dakota into the
   Nebraska Panhandle

   Concerning...Tornado and Severe Thunderstorm Watches 406...407...

   Valid 280010Z - 280145Z

   The severe weather threat for Tornado and Severe Thunderstorm
   Watches 406, 407 continues.

   SUMMARY...Isolated to widely scattered convection continues to pose
   a risk for primarily large hail and damaging wind gusts.

   DISCUSSION...Isolated to widely scattered supercells have developed
   across far southwestern South Dakota and northwestern Nebraska as of
   2350 UTC to the west of a diffuse dryline. In the near-term, the
   primary risk associated with this convection will be large to very
   large hail (perhaps to 2.5+ inches in diameter) given strong
   effective shear, elongated hodographs, and ample buoyancy within the
   hail growth zone (as supported by SHIP values ranging form 1-3+ per
   latest objective analysis). Recent high-res guidance and regional
   radar imagery suggest that rapid upscale growth may occur with the
   ongoing convection across southwestern South Dakota, which would
   favor a transition towards damaging/severe wind gusts as the primary
   risk. Farther south, ongoing convection is likely to remain more
   isolated within the Nebraska Panhandle, with large to very large
   hail and damaging wind gusts being possible with supercells.
   Additional development farther south into southwestern Nebraska
   remains uncertain at this time.

   Some increase in tornado potential may occur with time and as
   convection progresses eastward given greater moisture to the east of
   the diffuse dryline and a strengthening nocturnal low-level jet that
   will yield increasingly clockwise-curved low-level hodographs. A
   more linear storm mode and greater convective inhibition/capping to
   the east of the dryline lend uncertainty to the magnitude of the
   tornado risk, however. The greatest risk for a tornado is likely to
   occur with any discrete supercell that can persist farther east into
   this evening.

   ..Chalmers.. 06/28/2026

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

   ATTN...WFO...LBF...UNR...BOU...CYS...

   LAT...LON   42850344 43350333 44010309 44450267 44570214 44510176
               44290145 43770139 42630136 41790140 41220147 40990164
               40850201 40800247 41030294 41680332 42170338 42850344 

   MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
   MOST PROBABLE PEAK WIND GUST...65-80 MPH
   MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN