937
ACUS11 KWNS 211801
SWOMCD
SPC MCD 211801
SDZ000-NEZ000-212100-

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