SPC MD 1778


MD 1778 Image

Mesoscale Discussion 1778
NWS Storm Prediction Center Norman OK
0919 AM CST Tue Nov 10 2020

Areas affected...parts of north-central IA...southern MN...northwest

Concerning...Freezing rain 

Valid 101519Z - 102015Z

SUMMARY...Freezing rain rates exceeding 0.05 inch per 3 hours are
expected to shift northeast from near the IA/MN border this morning
and eventually into parts of northwest WI by early afternoon.

DISCUSSION...Radar mosaic this morning shows a precipitation shield
moving northeastward from north-central IA into southern MN.  A
surface cold front is displaced several hundred miles to the
southeast of this region.  Temperatures this morning are
sub-freezing and generally in the 30-32 deg F range from northern IA
northeastward into northwest WI.

Water-vapor imagery shows a powerful mid-level shortwave trough over
the central Great Plains and this disturbance is forecast to move
into western IA by the early to mid afternoon.  Concurrently,
strengthening frontogenetic forcing at 850 mb will overspread
southern MN through the remainder of the morning and into northwest
WI during the 12pm-3pm CST period.  As the column saturates over
southern MN into northwest WI, a warm layer at or above freezing
between 900-700 mb is forecast above a shallow sub-freezing layer
near the surface.  As a result, freezing rain will be the preferred
precipitation type in a several county-wide corridor from
south-central MN into northwest WI over the next 5 hours.

..Smith.. 11/10/2020

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


LAT...LON   43299363 43389494 46209133 45929018 43299363 

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