Storm Prediction Center Mesoscale Discussion 1651

   Mesoscale Discussion 1651
   NWS Storm Prediction Center Norman OK
   0236 PM CDT Sat Jul 18 2026

   Areas affected...Western Montana...central Idaho

   Concerning...Severe potential...Watch possible 

   Valid 181936Z - 182100Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Isolated to widely scattered severe thunderstorms are
   expected this afternoon and early evening with a risk for damaging
   gusts and large hail. Trends in storm coverage will be monitored and
   a Severe Thunderstorm Watch is possible.

   DISCUSSION...Isolated strong thunderstorms have developed in the
   vicinity of the ID/MT border west or Butte as of 1930z. This area is
   along the fringe of somewhat stronger mid-level flow associated with
   an upper low over southern British Columbia, and within a plume of
   monsoonal moisture along the periphery of an expansive mid-level
   ridge. Moderate instability, characterized by MLCAPE of 1000 to 1500
   J/kg and 35-45 kts of southwesterly shear will be favorable for
   supercell and multicell storm structures. Damaging gusts,
   potentially in excess of 75 mph, will be the primary risk. Large
   hail is also possible with any persistent supercell. 

   The primary uncertainty is storm coverage, and trends will continue
   to be monitored for the possibility of a Severe Thunderstorm Watch
   this afternoon.

   ..Bunting/Thompson.. 07/18/2026

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

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

   LAT...LON   45571206 45261354 45321433 45411502 45531516 46111510
               46611448 46991369 47501273 47721194 47861104 47541065
               47211059 46501080 45761175 45571206 

   MOST PROBABLE PEAK WIND GUST...65-80 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN