Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
355 PM EST Wed Feb 03 2021

Valid 00Z Thu Feb 04 2021 - 00Z Sun Feb 07 2021

...Central Plains to the Great Lakes...
Days 1-3...
An amplified upper trough will move into the Plains overnight -
driving a strong cold front south and east through the northern
and central Plains into the Mississippi valley Thursday morning. 
A brief period of rain or a wintry mix, followed by a changeover
to snow is expected across the mid Missouri into the mid and upper
Mississippi valleys as the front pushes east Thursday morning. 
While widespread heavy snowfall accumulations are not expected,
there remains a good signal that strong low-to-mid level
frontogenesis along with favorable upper jet forcing will likely
produce at least a brief period of heavy snowfall, especially
across portions of Iowa and southern Minnesota, into Wisconsin,
northern Illinois and the western U.P. of Michigan - where WPC
PWPF shows high probabilities for accumulations of 4-inches or
more during the Day 1 period (ending 00Z Friday).  The wintry mix
expected on the onset is expected to produce minor ice
accumulations across portions of the upper Mississippi valley into
the upper Great Lakes before precipitation changes over to the
snow.  By late Thursday, phasing energy aloft will support an
intensifying low that will translate northeast across the upper
Great Lakes.  Northwesterly flow is expected contribute to some
lake-enhanced snows across the western U.P. of Michigan by late
Friday.  Then as the low continues north of the Lakes, deep
northwesterly to westerly flow is expected to support the
development lake effect snows along the U.P. snow belts, as well
as along the eastern shores of Lake Michigan.  Deep cyclonic flow
will continue to support periods of lake effect snow shows in the
lee of the upper Great Lakes through Saturday.  WPC PWPF indicates
that three day totals of a foot or more are likely across portions
of the U.P. and along the northeastern shores of Lake Michigan. 
Meanwhile, much colder air spreading east, along with low level
southwesterly to westerly flow will support the development of
lake effect snows east of Lake Erie and Ontario on Saturday.

...Central Rockies...
Day 1...
A strong cold front, along with a well-defined shortwave moving
into the base of the longer wave trough, will support heavy snows
moving south across the central Rockies Wednesday evening, with
locally heavy accumulations possible across the western to central
Colorado and northern New Mexico ranges.

...Northern and Central Rockies...
Days 2-3...
A series of shortwaves embedded within strong northwesterly flow,
along with a strong cold front settling southwest, will support
periods of snow, with locally heavy accumulations expected across
portions of the northern into the central Rockies on Friday and
Saturday.  Areas impacted are expected to include the northern
Idaho, the western to central Montana, the western and southern
Wyoming ranges and the northwestern Colorado ranges.  WPC PWPF
indicates that two day totals of 8-inches or more are likely
across these areas. 

Pereira