SPC MD 1494

MD 1494 CONCERNING SEVERE THUNDERSTORM WATCH 439... FOR UPPER MISSISSIPPI VALLEY

Mesoscale Discussion 1494
NWS Storm Prediction Center Norman OK
0728 PM CDT Fri Aug 14 2020

Areas affected...Upper Mississippi Valley

Concerning...Severe Thunderstorm Watch 439...

Valid 150028Z - 150200Z

The severe weather threat for Severe Thunderstorm Watch 439
continues.

SUMMARY...Severe threat will shift slowly east this evening.

DISCUSSION...Severe threat is shifting east across ww439. Frontal
convection has grown upscale over the last few hours with a
near-continuous squall line now evident from St. Louis County-arcing
southwest into Brown County MN. This line is moving east at roughly
30-35kt and will soon spread east of the MS River into western WI.
However, air mass downstream over WI is notably more stable as the
ongoing squall line is currently moving through the instability
axis. Even so, large-scale forcing ahead of progressive short-wave
trough should maintain this linear MCS as it translates east. The
primary severe threat should become mostly wind due to the linear
structure.

..Darrow.. 08/15/2020

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

ATTN...WFO...DLH...ARX...MPX...

LAT...LON   44469430 46349294 47619246 47369167 45429203 44109309
            44469430 

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