SPC MD 1717

MD 1717 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PARTS OF EAST CENTRAL MINNESOTA...NORTHERN WISCONSIN AND WESTERN UPPER MICHIGAN

Mesoscale Discussion 1717
NWS Storm Prediction Center Norman OK
0517 PM CDT Sat Sep 26 2020

Areas affected...Parts of east central Minnesota...northern
Wisconsin and western Upper Michigan

Concerning...Severe potential...Watch possible 

Valid 262217Z - 270015Z

Probability of Watch Issuance...40 percent

SUMMARY...Increasing thunderstorm development appears likely in a
corridor across northern Wisconsin and adjacent western Upper
Michigan through 7-9 PM CDT.  This activity probably will pose a
risk for severe hail, and perhaps increasing potential for strong
wind gusts later this evening.

DISCUSSION...A fairly significant mid-level short wave trough is
just now beginning to dig into the northern Great Plains, but a
number of lower-amplitude perturbations precede it within broadly
cyclonic downstream flow into the upper Great Lakes region.  One
appears to be aiding recent new thunderstorm development
north/northeast of the Minneapolis MN area.  This activity appears
focused and rooted within lower/mid tropospheric warm advection,
near the nose of a plume of warm elevated-mixed layer air.  

This may be occurring mostly north of the steeper mid-level lapse
rates, where most unstable CAPE may not exceed 500 J/kg.  But
mid-levels are relatively cool, and model forecast soundings
indicate vertical shear within the convective layer supportive of
supercells.  Large hail appears the primary initial severe threat,
but there appears potential for upscale convective growth as
activity increases in coverage and develops eastward across northern
Wisconsin through 00-02Z.  If this occurs, the evolution of a small,
organizing convective cluster is possible and could be accompanied
by increasing potential for strong surface gusts.

..Kerr/Hart.. 09/26/2020

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

ATTN...WFO...MQT...GRB...DLH...ARX...MPX...

LAT...LON   45769298 46059168 46419040 46678844 45888746 45438834
            45148970 44819158 44899297 45769298 

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from SPC Forecast Products http://www.spc.noaa.gov/products/md/md1717.html