SPC MD 1604

MD 1604 CONCERNING SEVERE THUNDERSTORM WATCH 460... FOR FAR SOUTHEAST MONTANA INTO WESTERN SOUTH DAKOTA.

Mesoscale Discussion 1604
NWS Storm Prediction Center Norman OK
0920 PM CDT Thu Aug 27 2020

Areas affected...far southeast Montana into western South Dakota.

Concerning...Severe Thunderstorm Watch 460...

Valid 280220Z - 280345Z

The severe weather threat for Severe Thunderstorm Watch 460
continues.

SUMMARY...Severe thunderstorms ongoing across portions of WW460 are
expected to continue with a threat for damaging winds and large hail
this evening. Upscale growth into an MCS appears probable with an
increasing risk for damaging winds downstream where a new watch is
likely later this evening.

DISCUSSION...Several clusters of severe storms are currently ongoing
across WW460 this evening. Recent reports of severe hail and wind
gusts in excess of 70 mph signal continued organization of storms
across South Dakota. The 00z UNR sounding shows an environment
supportive of severe thunderstorms (including supercells) with 2000
J/kg of MLCAPE and 55 kts of effective shear. 8.5-9 C/km mid-level
lapse rates and supercell wind profiles suggest the threat for large
to very large hail will likely continue for a few more hours, before
upscale growth associated with the low-level jet and storm mergers
shifts the threat toward damaging winds. A downstream watch is
likely by 04z as cluster of storms is expected to organize into an
MCS across southern South Dakota later this evening. 

Across southern North Dakota, some hi-res guidance has shown an
increase in convective coverage between 03-04z. Despite the
increasing inhibition, 1000-1500 J/kg of MUCAPE would support some
severe potential, primarily in the form of damaging winds and
occasional severe hail, with any storm clusters that are able to
organize.

..Lyons/Guyer.. 08/28/2020

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

ATTN...WFO...FSD...ABR...BIS...UNR...BYZ...

LAT...LON   46780338 46740196 46650085 45379886 44299848 43069917
            43060285 43760430 44780452 45620430 46780338 

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from SPC Forecast Products http://www.spc.noaa.gov/products/md/md1604.html