Storm Prediction Center Mesoscale Discussion 1018

   Mesoscale Discussion 1018
   NWS Storm Prediction Center Norman OK
   0612 PM CDT Sun Jun 07 2026

   Areas affected...southeastern MT...northwest South Dakota and
   western North Dakota

   Concerning...Severe Thunderstorm Watch 285...

   Valid 072312Z - 080045Z

   The severe weather threat for Severe Thunderstorm Watch 285
   continues.

   SUMMARY...Supercells over southeastern MT are showing initial signs
   of upscale growth. An organized cluster or bow may result. The
   environment is favorable for a significant damaging wind risk (gusts
   greater than 75 mph) which may begin in the next 1-2 hours.

   DISCUSSION...Across PDS SVR Watch #285, initial supercell clusters
   have remained severe with large hail, but have shown signs of
   consolidation. The environment remains strongly unstable and sheared
   with MLCAPE in excess of 2500 J/kg and 45-55 kt of deep-layer shear
   supporting organized and intense thunderstorms. T/TD spreads as
   highs 40 degrees F will favor strong downdrafts with the potential
   for severe outflow winds. This, combined with enhanced convergence
   near the frontal boundary will favor numerous storm interactions and
   the development of new updrafts in close proximity to the ongoing
   storms. 

   Exact convective evolution remains somewhat unclear, but initial
   upscale growth is likely occurring. This is supported by the change
   in radar presentation of the storms over southern Custer County in
   MT, with multiple strong updrafts observed and lengthening storm
   motion vectors. If a sufficient cold pool can organize, a highly
   organized cluster or bowing complex may result. Given the very
   favorable environment, this would support a significant damaging
   wind risk with gusts greater than 75 mph. CAM trends along with the
   aforementioned observational data suggest this is likely in the next
   30-90 minutes.

   ..Lyons.. 06/07/2026

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

   ATTN...WFO...ABR...BIS...UNR...BYZ...GGW...

   LAT...LON   46140547 46810401 46960313 46760231 46460197 45750167
               44930258 44800334 44730455 44890525 45350554 45770563
               46140547 

   MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
   MOST PROBABLE PEAK WIND GUST...75-90 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN