Storm Prediction Center Mesoscale Discussion 1535

   Mesoscale Discussion 1535
   NWS Storm Prediction Center Norman OK
   0559 PM CDT Tue Jul 07 2026

   Areas affected...Southern/southeast Montana into far northern
   Wyoming

   Concerning...Severe potential...Watch possible 

   Valid 072259Z - 080100Z

   Probability of Watch Issuance...40 percent

   SUMMARY...An environment favorable for supercells remains in place
   across southeast Montana, and new updraft development is noted
   across the region. It is uncertain how many storms will develop, but
   some severe hail and wind risk may materialize in the coming hours.

   DISCUSSION...Latest GOES day cloud phase imagery shows several
   attempts at initiation along the terrain in central to southeast
   Montana within a weak upslope flow regime. Earlier attempts at deep
   convection have struggled to intensify away from the terrain, but
   synoptic-scale ascent continues to overspread the region as a
   mid-level wave traverses the international border. Recent HRRR and
   RAP forecast soundings appear to be capturing the near-storm and
   downstream environments well and depict very limited inhibition in
   place, which suggests that deep/robust convection remains possible
   if storms can be maintained away from their zones of ascent. 

   In general, the downstream environment can be characterized as
   favorable for supercell development given around 1000-1500 J/kg
   MLCAPE and 30-35 knots of effective bulk shear, and more aggressive
   members of the HRRR/RRFS time-lagged ensemble depict at least
   isolated supercell development through 02 UTC. However, these same
   ensemble solutions show generally low thunderstorm coverage and low
   probabilities for intense convection, which reflects the uncertainty
   pertaining to thunderstorm maintenance away from the terrain. Trends
   will continue to be monitored, and watch issuance may be needed if
   it appears likely robust storms will be sustained within the open
   warm sector.

   ..Moore/Gleason.. 07/07/2026

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

   ATTN...WFO...UNR...BYZ...GGW...RIW...TFX...

   LAT...LON   44640691 45060812 45390881 45820908 46580907 47170900
               47500878 47620838 47640793 47470738 47170680 46390541
               46080511 45600497 45210511 44820558 44650594 44590629
               44640691 

   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN