SPC MD 1113


MD 1113 Image

Mesoscale Discussion 1113
NWS Storm Prediction Center Norman OK
0724 PM CDT Sun Jul 05 2020

Areas affected...northeast WY...western SD

Concerning...Severe Thunderstorm Watch 332...

Valid 060024Z - 060130Z

The severe weather threat for Severe Thunderstorm Watch 332

SUMMARY...The propensity for severe gusts will continue to increase
with a thunderstorm band moving east-northeast from northeast WY
into southwest SD.  Large hail is possible with discrete supercell
activity from northeast WY into northwest SD over the next hour.

DISCUSSION...Radar mosaic as of 0020z shows a congealing band of
storms over Niobrara, Converse, and Weston counties in WY as this
activity moves to the east-northeast and approaches the Black Hills
later this evening.  The 00z Rapid City observed sounding showed
steep mid-level lapse rates (8.6 degrees C/km in the 700-500mb
layer) with 40-kt 500mb flow increasing to above 50 kt around 300mb.
Surface analysis indicates although some convective overturning has
occurred with earlier storms near the Black Hills, it appears the
airmass has not been appreciably modified with the rain-cooled air. 
Therefore it seems likely a moist/unstable boundary layer is in
place ahead of the band of storms over northeast WY moving into SD
over the next few hours.  The risk for 60-75 mph gusts will
continue.  Large hail 1.0-2.5 inches in diameter is also possible
with discrete supercells over the next hour from northeast WY into
northwest SD and far southwest ND.

..Smith.. 07/06/2020

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


LAT...LON   44180627 46220267 46190191 45740228 44740401 43750288
            42900359 42680449 44180627 

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