Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
344 AM EST Thu Mar 03 2022

Valid 12Z Thu Mar 03 2022 - 12Z Sun Mar 06 2022

...West...
Days 1-3...
Thursday into early Friday is expected to be fairly quiet with
respect to snow.  Apart from potentially locally heavy amounts
associated with a northern stream shortwave moving into the
northern Rockies Friday morning, heavy snow accumulations are not
expected.  For the Day 1 period ending 12Z Friday, WPC
probabilities indicate some likely accumulations of 4 inches or
more in the Glacier National Park region in northwestern Montana.

Beginning Friday morning and continuing into Saturday, the
potential for more widespread significant snows is expected to
increase as a pair of upper systems impact the western U.S. 
Models show an upper low developing off the coast and moving
across Southern California Friday morning before transitioning to
an open wave and ejecting east across the Four Corners region into
the central Rockies during the evening and overnight.  This is
expected to produce mainly light accumulations from the higher
elevations of the Southern California mountains to the central
Rockies.  This system will be followed by another upper low that
is forecast to develop along the Pacific Northwest coast on Friday
before dropping into Northern California and Nevada Saturday
morning. This is forecast to bring more significant snows into the
Sierra, with the WPC probabilities indicating widespread potential
for accumulations of the 4-8 inches, with locally heavier amounts
across the high terrain by 12Z Saturday.

This second system is expected to drop southeast across Nevada on
Saturday before turning east along the Utah-Arizona border
Saturday night.  This will bring the potential for significant
snows across the Great Basin into the central Rockies.  WPC
probabilities indicate accumulations of the 4-8 inches are likely
across the higher elevations of the central to eastern Nevada and
Utah ranges, as well as the San Juan mountains.

...Central High Plains through the Upper Midwest...
Day 3...
Models continue to show a two-phase event impacting portions of
Nebraska, the Dakotas and Upper Great Lakes region Saturday into
early Sunday.  Guidance shows a weak shortwave ejecting out of the
base of the western U.S. trough lifting across the Upper Midwest
Saturday morning.  This is expected to bring a mixture of snow and
ice from portions of eastern Nebraska and South Dakota to northern
Michigan.  Meanwhile, the previously noted shortwave moving across
the southwestern U.S. on Friday is forecast to lift northeast
across the central Rockies and into the High Plains Saturday
morning.  Favorable upper jet forcing is expected to help support
precipitation developing on the northwest side of the associated
surface low as it moves from eastern Colorado Saturday morning,
with some potential for heavy snow developing over the
southeastern Wyoming mountains.  Models show favorable upper
forcing supporting a deepening surface low with an accompanying
commahead as it moves across the Upper Midwest-Great Lakes
Saturday night.  Heaviest precipitation is expected to fall in the
form of a wintry mix, with significant icing possible across
portions of northern Wisconsin and Upper Michigan.  WPC
probabilities indicate ice accumulations of 0.10 inch or more are
likely in some spots.  The greatest threat for significant snow
accumulations lies farther to the north and west, with WPC
probabilities indicating moderate potential (40-70 percent) for
snow accumulations of 4 inches from southeastern North
Dakota/northeastern South Dakota to the Minnesota Arrowhead.

Pereira