Storm Prediction Center Mesoscale Discussion 1381

   Mesoscale Discussion 1381
   NWS Storm Prediction Center Norman OK
   0132 PM CDT Fri Jun 20 2025

   Areas affected...parts of southwest into west-central Montana

   Concerning...Severe potential...Watch unlikely 

   Valid 201832Z - 202130Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Scattered storms will form over much of southwest Montana
   and into Idaho, and spread northeastward toward central Montana.
   Scattered strong to severe gusts along with marginal hail may occur.

   DISCUSSION...Visible satellite imagery shows strong heating over
   much of the region ahead of the upper trough/midlevel temperature
   gradient. The exception is north of the stationary front near GTF
   where thick low-level clouds exist with cool north winds. Convection
   is already increasing over the higher terrain from central ID into
   southwest MT, and more substantial storms are likely to develop by
   about 20-21Z. 

   GPS PWAT sensors currently indicate around 0.80-0.95 inches, which
   is sufficient to support robust convection given steepening lapse
   rates. Deep-layer shear around 50 kt may support cells producing
   isolated hail near severe thresholds. While temperatures are cooler
   downstream, some of that air should mix out given persistent
   boundary layer mixing/heating upstream. Moderate winds aloft and
   steepening boundary layer lapse rates may support
   northeastward-moving bowing structures capable of producing damaging
   gusts toward central MT.

   ..Jewell/Hart.. 06/20/2025

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

   ATTN...WFO...BYZ...TFX...MSO...

   LAT...LON   46531391 47091288 47351210 47631068 47521003 46871004
               46001085 45551131 45391155 44861253 44641358 44961425
               45231454 45771465 46041451 46531391 

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