SPC MD 1606

MD 1606 CONCERNING SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY FOR SOUTHERN MN AND FAR NORTHERN IA

Mesoscale Discussion 1606
NWS Storm Prediction Center Norman OK
0128 AM CDT Fri Aug 28 2020

Areas affected...southern MN and far northern IA

Concerning...Severe potential...Severe Thunderstorm Watch likely 

Valid 280628Z - 280800Z

Probability of Watch Issuance...95 percent

SUMMARY...Damaging winds are expected to continue for several hours
early this morning as storms track eastward across southern MN. A
severe thunderstorm watch will be issued soon for portions of the
MCD area.

DISCUSSION...A severe MCS is tracking eastward across eastern SD at
around 45-50 kt as of 1 am CDT. Several measured severe gusts
greater than 75 mph have been recorded over the past few hours. The
most recent significant severe gust was measured at he Huron SD ASOS
at 84 mph. 

Downstream, surface dewpoints in the upper 60s to near 70 F are
present across southern MN, decreasing to the low-to-mid 60s F
northward toward central MN. 00z RAOBs from MPX and ABR indicate
modest midlevel lapse rates atop the moist boundary layer, with some
dry air noted in the 850-700 mb layer, giving thermodynamic profiles
typically seen with intense damaging-wind potential. While low-level
flow is not particularly strong, a 20-30 kt south/southwesterly 850
mb low level jet is noted in mesoanalysis and regional VWP data.
Furthermore, strong effective shear will aid in maintaining MCS
organization as the system tracks eastward along an instability
gradient across southern MN. 

With the expectation that severe gusts, some possibly greater than
64 kt, will continue into southern MN for the next several hours, a
downstream severe thunderstorm watch will be needed soon as
convection is expected to move across the SD border into MN by
around 730z.

..Leitman/Edwards.. 08/28/2020

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

ATTN...WFO...ARX...MPX...DMX...FSD...ABR...

LAT...LON   43189606 43569665 44679672 45459657 45589606 45189398
            44939314 44749280 44369282 43869304 43389355 43199445
            43189606 

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from SPC Forecast Products http://www.spc.noaa.gov/products/md/md1606.html