Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
308 PM EST Sat Jan 29 2022

Valid 00Z Sun Jan 30 2022 - 00Z Wed Feb 02 2022

...Northeast...
...Powerful Nor'easter/Blizzard lifts into Atlantic Canada
tonight...

The powerful low pressure system will remain near peak intensity
as it lifts north from a point off Cape Cod through tonight.

Strong ascent supported by a coupled upper jet, low-to-mid level
frontogenesis, and ocean enhancement that has produced repeating
very heavy bands over southeast MA/RI (with 2 to 3" hourly
snowfall) will persist through the next couple hours before
largely tapering off by 00Z.

The loss of ocean enhancement farther north, over Maine, will
limit hourly snowfall to generally 1 to 2" tonight as the bands
orient more north-south and lift over roughly the central Maine
coast to northeastern Maine (around Presque Isle) where Day 1 snow
probabilities (after 00Z) are moderate for over 6" additional snow.

The threat for snow is pretty much over by 12Z as the system races
through Atlantic Canada.


...Pacific Northwest to the Northern Rockies...
Days 1-3...

An upper low crossing the Gulf of Alaska today will transition to
an open wave, with a potent remnant shortwave trough sliding down
the AK/BC coast to WA through Sunday before shifting across the
northern Rockies Sunday night with a similar tracking reinforcing
trough crossing the same areas Monday. This will drive a front and
the return of precipitation, including mountain snow, into the
Northwest with snow levels 3500ft to 4000ft through Sunday before
dropping do around 1000ft Sunday night through Monday. WPC
probabilities are high for accumulations over 6" for both Day 1.5
and Day 2.5 for the northern Cascades (including the Stevens and
Snoqualmie passes), Bitterroots, and Ranges near Glacier NP.

For days 1-3, the probability of significant icing is less than 10
percent.

Jackson


~~~ Key Messages for Jan 28-30 Blizzard ~~

-- A major Nor'easter will lift north off Maine tonight.

-- Additional snowfall of 6 to 12 inches is expected tonight over
eastern Maine.

-- Dangerous wind chills continue across the Northeast into
Sunday.