Storm Prediction Center Mesoscale Discussion 1543

   Mesoscale Discussion 1543
   NWS Storm Prediction Center Norman OK
   0239 PM CDT Wed Jul 08 2026

   Areas affected...portions of southeastern Montana and northern
   Wyoming into far western South Dakota

   Concerning...Severe potential...Watch possible 

   Valid 081939Z - 082145Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Widely scattered, high-based thunderstorms will pose a
   risk for damaging/severe wind gusts and isolated large hail this
   afternoon and evening. Trends are being monitored for a potential
   Severe Thunderstorm Watch.

   DISCUSSION...Scattered, high-based thunderstorm development is
   ongoing across the high-terrain of southern Montana and northern
   Wyoming as of 1930 UTC. Continued insolation amid modest low-level
   moisture (dewpoints ranging from the mid-40s to low-50s F) will
   continue to support an increase in thunderstorm coverage through the
   afternoon. Modifying the 18z RIW observed sounding for recent
   observations depicts steep low- and mid-level lapse rates with
   MLCAPE of 500-1000 J/kg. This dry boundary layer profile will
   support efficient evaporative cooling and cold pool development,
   with recent high-res guidance continuing to suggest the development
   of one or more linear clusters/segments through the afternoon. As
   this occurs, an increase in the threat for damaging/severe wind
   gusts is expected as convection progresses eastward amid deep-layer
   westerly flow. Isolated large hail also cannot be ruled out with the
   strongest cores given steep mid-level lapse rates and modest
   effective shear of 25-30 kts. 

   While the general expectation is for the severe risk to remain more
   limited in coverage compared to areas farther south across the
   central High Plains, a Severe Thunderstorm Watch may be needed in
   the next 1-2 hours should a corridor of greater severe potential
   become evident.

   ..Chalmers/Hart.. 07/08/2026

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

   ATTN...WFO...UNR...BYZ...RIW...

   LAT...LON   43530526 43480807 43680886 43990968 44441043 44741072
               45031085 45591070 45831015 46090865 46020696 45590542
               45100404 44730370 44260363 43900375 43670431 43530526 

   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN