Storm Prediction Center Mesoscale Discussion 1509

   Mesoscale Discussion 1509
   NWS Storm Prediction Center Norman OK
   0128 PM CDT Sun Jun 29 2025

   Areas affected...eastern WY...the NE Panhandle ...southwest SD

   Concerning...Severe potential...Severe Thunderstorm Watch likely 

   Valid 291828Z - 292030Z

   Probability of Watch Issuance...95 percent

   SUMMARY...At least isolated large hail and severe gusts are likely,
   with scattered coverage possible by late afternoon. A Severe
   Thunderstorm Watch issuance is expected.

   DISCUSSION...Initial, lower-topped convection has formed across far
   southeast MT towards the Black Hills. This activity is expected to
   strengthen over the next couple hours amid modest MLCAPE near 1000
   J/kg and effective bulk shear around 40 kts. While the parameter
   space is a step-down from yesterday, which should mitigate overall
   intensity, the coverage of storms should be greater by peak heating.
   Additional storms should develop within the weak upslope flow regime
   across southeast WY. Both areas may eventually converge in the NE
   Panhandle to far southwest SD vicinity by early evening. A few
   supercells with large hail are most likely in the northern regime
   surrounding the Black Hills. Severe gusts may be the primary hazard
   farther south where multicell clustering dominates.

   ..Grams/Hart.. 06/29/2025

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

   ATTN...WFO...LBF...UNR...CYS...BYZ...RIW...

   LAT...LON   45350502 44520346 43690208 42970166 42050152 41470218
               41160293 41120431 41070513 42440530 43820586 44550635
               45350502 

   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN