Storm Prediction Center Mesoscale Discussion 1356

   Mesoscale Discussion 1356
   NWS Storm Prediction Center Norman OK
   0615 PM CDT Sat Jun 27 2026

   Areas affected...parts of eastern Montana into the western Dakotas

   Concerning...Severe Thunderstorm Watch 405...408...

   Valid 272315Z - 280115Z

   The severe weather threat for Severe Thunderstorm Watch 405, 408
   continues.

   SUMMARY...Storms posing a risk for large hail and localized
   downbursts will transition to primarily broader swaths of strong to
   severe wind gusts through 6-8 PM MDT.

   DISCUSSION...Forcing for ascent associated with one or two short
   wave impulses pivoting around the eastern periphery of the
   large-scale upstream low continues to support increasing
   thunderstorm development off the higher terrain and within the lee
   surface troughing.  This includes a couple of notable clusters
   spreading north and northeast of the Big Horns and one progressing
   across the northeastern international border area.  Strongest
   boundary-layer instability is focused in higher moisture content to
   the east of the surface trough axis, but modestly moist upslope flow
   to the west of the trough axis appears unstable enough to maintain
   upscale growth during the next few hours.

   Gradually, the severe hail and localized damaging downburst threat
   will shift to primarily a broader strong to severe gust threat with
   enlarging, strengthening and consolidating surface cold pools, which
   should tend to surge east-northeastward toward the western Dakotas
   state border vicinity as they consolidate toward 00-02Z.

   ..Kerr.. 06/27/2026

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

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

   LAT...LON   48770447 47440326 45400399 45510628 47470652 48120623
               48770447 

   MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
   MOST PROBABLE PEAK WIND GUST...75-90 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN