Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
422 AM EDT Sun Mar 13 2022

Valid 12Z Sun Mar 13 2022 - 12Z Wed Mar 16 2022

...Pacific Northwest...
Days 1-3...

The first of two distinct shortwaves has moved onshore
Washington/Oregon overnight, accompanied by Pacific jet energy and
a surface cold front. This feature will dig southward towards the
Four Corners region today, with shortwave ridging following close
behind into the Pacific Northwest later today. This will allow
heavy snowfall to gradually taper off from west to east. Prior to
the end of heavy snowfall, WPC probabilities are high for 6+
inches in the Oregon Cascades, with moderate probabilities
extending into the Blue Mountains, the Sawtooth, parts of the
Northern Rockies, the Tetons, and the Wind Rivers. Moderate
probabilities also look to extend farther south into the Uinta and
Elk Mountains of Utah and Colorado, respectively, as the shortwave
digs southward. The second shortwave/impulse will be less compact
and displaced a bit farther north than the lead shortwave, and WPC
probabilities for more than 6 inches are high in the WA Cascades
and Olympics on D2/D3 in association with the shortwave. This
secondary impulse looks to open up into a large scale trough on
D3, and moderate probabilities then extend into the Northern
Rockies, the Sawtooth, and the Tetons once again.


...Upper Midwest...
Day 2...

A potent jet streak racing west to east across the Northern Plains
and Upper Midwest will drive ascent atop an elevated baroclinic
gradient north of a cold front sinking into the Mid-Mississippi
Valley. A weak wave of low pressure along this front will shift
southeast, driving subtly enhanced warm advection which will
isentropically ascend the Canadian high to produce an expanding
precipitation shield from North Dakota through the western Great
Lakes. The most robust overlap of forcing and moisture is likely
from eastern MN through the U.P. and into the northern L.P. of MI,
where some enhanced fgen is likely to drive heavier snow rates.
This feature will move quickly eastward, but WPC probabilities for
more than 4 inches have increased to as high as 10-30% in a narrow
corridor from WI through the U.P. of MI.


Churchill/Weiss