Storm Prediction Center Mesoscale Discussion 1370

   Mesoscale Discussion 1370
   NWS Storm Prediction Center Norman OK
   0744 PM CDT Sun Jun 28 2026

   Areas affected...parts pf northwestern Nebraska into southwestern
   South Dakota

   Concerning...Severe potential...Watch possible 

   Valid 290044Z - 290315Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Increasing strong thunderstorm development appears
   probable by late evening, if not earlier.  This may, at least
   initially, include evolving supercells with large hail and at least
   some potential for  tornadoes.  Although timing remains a bit
   uncertain, it is appearing more probable that a severe weather watch
   will be needed at some point this evening.

   DISCUSSION...Within larger-scale mid/upper troughing across the
   West, another significant short wave trough is now turning eastward
   through the eastern Great Basin and will continue to gradually pivot
   east-northeastward through this evening.  This may be preceded by
   one or two much more subtle perturbations within downstream cyclonic
   flow across the Colorado Rockies toward the Black Hills vicinity,
   with at least attempts at isolated thunderstorm development now
   underway northwest of Mullen NE.

   This storm appears to be developing near the leading edge of
   westerly low-level moisture return toward the high plains between
   the Cheyenne Ridge and Black Hills vicinity, where forcing for
   ascent associated with strengthening warm advection centered around
   the 700 mb level is forecast to focus by 02-04Z.  Coupled with
   strengthening deep-layer and low-level shear near the nose of an
   intensifying low-level jet (50-60+ kt around 850 mb), the potential
   for supercell thunderstorm development seems likely to increase
   through mid to late evening, aided by inflow of air characterized by
   increasingly sizable potential instability.

   ..Kerr/Thompson.. 06/29/2026

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

   ATTN...WFO...ABR...LBF...UNR...CYS...

   LAT...LON   43240344 44120131 42620001 42340153 41810252 41820354
               43240344 

   MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN