SPC MD 1747

MD 1747 CONCERNING HEAVY SNOW FOR NORTHEAST WI/CENTRAL UPPER MI

Mesoscale Discussion 1747
NWS Storm Prediction Center Norman OK
0706 PM CDT Tue Oct 20 2020

Areas affected...Northeast WI/central Upper MI

Concerning...Heavy snow 

Valid 210006Z - 210400Z

SUMMARY...Hourly snowfall rates approaching 1" will be possible
through about 05z, with a diminishing threat for locally heavy snow
thereafter.

DISCUSSION...In advance of a midlevel shortwave trough crossing the
upper MS Valley, a zone of strong low-midlevel warm advection is
ongoing across central/northern WI.  Ascent is resulting in
saturation and widespread precipitation formation from central WI
northward, and the combination of wet bulk cooling/melting has
resulted in surface temperatures near 32 F across northwest and
north central WI.  The zone of ascent and modest low-level cooling
will spread northeastward toward central Upper MI this evening in
tandem with the heavier precipitation rates, where snow is the
likely precipitation type.  The warm advection will tend to support
a broad zone of precipitation formation given the stable midlevel
lapse rates, with the heavier precipitation rates (and greater
snowfall potential) expected along and 1-2 counties north of the
surface 32 F line.  Though focused banding is not expected given
only weak frontogenesis, local snowfall rates could approach 1"/hour
before the snow diminishes from southwest-to-northeast across
central Upper MI toward about 05z.

..Thompson.. 10/21/2020

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

ATTN...WFO...MQT...GRB...ARX...

LAT...LON   46828776 46458769 46108776 45738786 45258825 44768889
            44508965 44769004 45309004 45778939 46898802 46828776 

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