SPC MD 1482

MD 1482 CONCERNING SEVERE THUNDERSTORM WATCH 434... FOR PORTIONS OF SOUTHERN ND AND NORTHERN SD

Mesoscale Discussion 1482
NWS Storm Prediction Center Norman OK
0212 AM CDT Fri Aug 14 2020

Areas affected...Portions of southern ND and northern SD

Concerning...Severe Thunderstorm Watch 434...

Valid 140712Z - 140845Z

The severe weather threat for Severe Thunderstorm Watch 434
continues.

SUMMARY...Large hail and severe wind gusts will remain possible with
storms moving eastward across southern North Dakota and northern
South Dakota early this morning.

DISCUSSION...A small cluster of semi-discrete storms is ongoing
along the ND/SD border early this morning ahead of a strong
shortwave trough over the northern Rockies/Plains. Effective bulk
shear around 45 kt shown on the 06Z BIS special sounding will
continue to support the supercell structures observed so far. Steep
mid-level lapse rates of 7.8 C/km were also observed on the 06Z BIS
sounding, which is promoting substantial MUCAPE to the south of a
reinforcing cold front draped across ND. Large hail will remain a
threat so long as storms remain semi-discrete. Severe winds from
thunderstorm downdrafts may also occur, as the near-surface stable
layer remains quite shallow. Multiple measured wind gusts of 55-65
mph have already been reported with this convection, and current
expectations are for similar values to remain possible for at least
the next couple of hours as storms generally track eastward along an
elevated instability gradient near the ND/SD border. The reinforcing
cold front across central ND will likely serve as a northern limit
for any meaningful severe threat.

..Gleason.. 08/14/2020

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

ATTN...WFO...ABR...BIS...UNR...

LAT...LON   45690286 45840327 46880214 46920060 46820012 46549986
            45929988 45720021 45690286 

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