SPC MD 1576

MD 1576 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PARTS OF SOUTHWESTERN THROUGH SOUTH CENTRAL MONTANA

Mesoscale Discussion 1576
NWS Storm Prediction Center Norman OK
0648 PM CDT Tue Aug 25 2020

Areas affected...Parts of southwestern through south central Montana

Concerning...Severe potential...Watch unlikely 

Valid 252348Z - 260145Z

Probability of Watch Issuance...5 percent

SUMMARY...Thunderstorms accompanied by strong to locally severe wind
gusts will likely be maintained east-northeast of the mountains of
southwestern Montana, through areas of south central Montana between
Billings and Lewistown by 7-8 PM MDT.

DISCUSSION...Aided by forcing for ascent associated with one of
several subtle short wave perturbations, migrating around the
northwestern periphery of prominent mid-level subtropical riding, at
least a couple of clusters of thunderstorms appear to be merging
with consolidating outflow.  This is now approaching the White
Sulphur Springs and Bozeman vicinities, embedded within 30-40 kt
deep-layer west-southwesterly mean ambient flow.  Associated
moderately strong deep-layer shear is contributing to convective
organization, which seems likely to persist at least into evening. 
Although a deeply mixed downstream boundary layer appears only
weakly unstable, in terms of CAPE, steep lower/mid tropospheric
lapse rates with large sub-cloud temperature/dew point spreads
likely will remain supportive of a continuing risk for strong to
locally severe wind gusts.  This will progress across the higher
terrain, through the Musselshell Basin vicinity by 02-03Z.

..Kerr/Grams.. 08/25/2020

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

ATTN...WFO...BYZ...GGW...TFX...MSO...

LAT...LON   45571288 46571126 47150904 47070705 46040711 45531021
            44981219 45571288 

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