Storm Prediction Center Mesoscale Discussion 513

   Mesoscale Discussion 0513
   NWS Storm Prediction Center Norman OK
   0101 PM CDT Mon Apr 21 2025

   Areas affected...parts of nwrn NE into s cntrl SD

   Concerning...Severe potential...Watch unlikely 

   Valid 211801Z - 212100Z

   Probability of Watch Issuance...5 percent

   SUMMARY...Scattered thunderstorm activity is beginning to develop
   this afternoon.  Although this is likely to remain weak in
   intensity, it may still contribute to a few locally strong to
   briefly severe strength surface gusts by 2-4 PM MDT.

   DISCUSSION...Within larger-scale mid-level troughing spreading
   across and east of the northern Rockies, it appears that one
   embedded speed maximum (50+ kt around 500 mb) will continue an
   east-northeastward propagation from east central Wyoming toward
   south central South Dakota this afternoon.  Despite limited
   low-level moisture, insolation beneath cold mid-level air (including
   temperatures cooling below -20C around 500 mb) is contributing to
   weak destabilization of the boundary layer, which continues to warm
   and deepen with insolation across the Sand Hills of Nebraska into
   the high plains south and east of the Black Hills.

   Deepening high-based convective development is underway, with
   lightning already noted in activity as far south as the Scottsbluff
   NE vicinity.  This probably will continue, with some additional
   intensification while spreading eastward through mid to late
   afternoon.  As boundary-layer mixing/deepening progresses, the
   sub-cloud environment will become increasingly conducive to the
   downward transfer of momentum associate with the stronger mid-level
   flow and the negatively buoyant downdrafts, contributing to
   potential for a few gusts in excess of 50 kt.

   ..Kerr/Hart.. 04/21/2025

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

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

   LAT...LON   44290180 44330078 43749980 42810038 41600227 41460368
               43030383 43290285 44150233 44290180 

   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN