Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
301 AM EST Mon Feb 14 2022

Valid 12Z Mon Feb 14 2022 - 12Z Thu Feb 17 2022


...Pacific Northwest through the Rockies...
Days 1-3...

An impressive closed mid-level low will dig out of the Gulf of
Alaska and shift onshore WA state today, and then continue to
track southward towards the Four Corners by late Tuesday into
Wednesday. A couple waves of low pressure along the southeast
moving cold front through the region will help focus areas of
heavier precipitation. For day 1, the focus is mainly on the
highest terrain areas of the OR/WA Cascades into the Northern
Rockies, Absarokas, Sawtooth, and ranges of NW WY. By late day 2
into day 3, deeper forcing for ascent coupled with terrain upslope
enhancement will help drive widespread moderate to heavy snowfall
for the southern to central Rockies.

WPC probabilities for 4 inches or more on day 1 are well above 90
percent for the OR/WA Cascades and generally above 60 percent for
the higher elevations of central ID to southwest MT ranges. Those
greater 4 inch snowfall probabilities reach the central Rockies on
day 3 where the highest peaks have 40-60 percent probabilities
this cycle. Lighter snows are also likely to be quite broad in
coverage on day 3, with WPC probabilities for more than 2 inches
over 30% continuing in the Northern Rockies and extending as far
south as the Mogollon Rim and White Mountains of AZ and east into
the High Plains of CO, including the I-25 corridor.


...Central Plains to Great Lakes...
Day 3...
Aforementioned shortwave energy dropping through the Four Corners
region begins to eject into the southern/central Plains late
Wednesday into Thursday morning. Height falls and broad upper
diffluence and its interaction with a lingering frontal boundary
in the region will promote cyclogenesis over portions of the
southern Plains after 00Z Thursday that tracks northeast through
the mid-MS River Valley. Colder air seeping southward on the heels
of stronger Canadian high pressure will set the stage for a wintry
mix as precipitation breaks out along the tightening baroclinic
zone northwest of the low center. Much uncertainty exists for the
track/speed/strength of the system among the deterministic and
ensemble guidance but potential exists for all winter weather
types ranging from snow to sleet to freezing rain. The bigger
winter storm threat exists beyond the current day 3 period but the
latest WPC probabilities already show a stripe of slight
probabilities for 2 inches or more, highest across southern
Wisconsin and northern Illinois into central Michigan where colder
air will be much deeper. A narrow corridor of freezing rain is
possible and the latest WPC freezing rain probabilities show near
30 percent probabilities of 0.1 inch accretion across portions of
Missouri into central Illinois.


Taylor