Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
422 AM EDT Fri Mar 18 2022

Valid 12Z Fri Mar 18 2022 - 12Z Mon Mar 21 2022

...Central Plains through the Upper Midwest...
Day 1...

A surface low will lift northeast along a front across MO today
and push toward Detroit tonight. Decent cold air advection behind
this front will help sharpen the elevated baroclinic gradient with
a closed upper level low developing today. A deformation axis NW
of the low will continue to allow a swath of precip with embedded
moderate rates to spread northeast from central KS across IS and
central WI today and northern MI this evening.
Dynamic cooling of the column in this swath of marginal thermal
conditions will allow snow to form, particularly with rates are
highest. Day 1 snow probabilities for over 2" are low to moderate
from southwest IA to the UP of MI.


...Northern New England...
Day 2...

Warm air advection ahead of the low reaching the Upper Midwest
this evening spreads light to locally moderate precip over New
England late tonight into Saturday night. Pockets of freezing rain
develop over VT/NH/Maine with Day 2 ice probabilities for over
0.1" moderate along the White Mtns of NH/Maine.


...The West...
Days 1-3...

An shortwave trough reaches the WA coast late tonight before
reaching down to the central CA coast by late Saturday with
further reinforcement Saturday night taking the base of the trough
into the Baja. This extra reinforcement allows the low to close
off Sunday night near the AZ/NM border Sunday night.   Ample
Pacific moisture along with lift from a cold front, PVA ahead of
the upper trough and increasing left exit diffluence downstream of
a powerful Pacific jet streak that pushes into the Pacific
Northwest Saturday night will produce widespread precip/mountain
snow along the front. This front pushes inland over the Pacific
Northwest coast late tonight, over northern CA Saturday and across
the northern Intermountain West through Sunday night. Lee side
cyclogenesis east of the southern Rockies begins late Sunday night
with potential for a notable snow potential for the southern High
Plains Monday depending on the track (see PMDEPD for more info).
Day 1.5/2 snow probabilities for over 6" are moderate for the
Cascades and Sierra Nevada and for Days 2.5/3 moderate values are
over the northern Rockies (in particular the Salmon River Mtns of
ID and the Tetons/Absarokas.

Decent cold air spills across the Northwest under the trough
through Sunday, but an atmospheric river approaches Sunday night
with snow levels rapidly increasing from 2000ft to 4000ft over the
WA Cascades. Moderate Day 3 probabilities for over 6" are in the
WA Cascades and Olympics.


Jackson