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

Valid 12Z Sat Jan 29 2022 - 12Z Tue Feb 01 2022


...Mid-Atlantic/Northeast...
Day 1...
...Powerful Nor'easter/Blizzard for the Mid-Atlantic and
Northeast...
Surface low pressure associated with an amplifying upper trough
over the eastern U.S. continues to strengthen off of the
Mid-Atlantic coast this morning, with a broad area of moderate to
heavy snow spreading north along the Mid-Atlantic coast into
southern New England.  The low will begin to rapidly intensify as
it tracks north through the morning.  General consensus of the
deterministic models show the low's central pressure dropping to
near or below 970 mb as it moves into the Gulf of Maine later
today.

Strong ascent supported by a coupled upper jet and low-to-mid
level frontogenesis will help promote impressive snowfall rates on
the northwest side of the low.  HREF guidance continues to show
the potential for snowfall rates of 2-4 inches/hour within the
resulting mesoscale bands developing over eastern Long Island,
southeastern New England, and then across coastal Maine later this
morning.  WPC probabilities continue to indicate widespread
accumulations of a foot or more are probable across this region,
with a local maxima likely centered over eastern Massachusetts.

Models continue to indicate this will be a fast-moving system,
with the threat for heavy snow quickly waning across the Northeast
as the system races into Atlantic Canada overnight.

...Pacific Northwest to the Northern Rockies...
Days 2/3...
An upper low dropping across the Aleutians into the Gulf of Alaska
this morning is expected to transition to an open wave, with the
remnant shortwave forecast to slide southeast into British
Columbia and the Pacific Northwest late Sunday.  This will drive a
front and the return of precipitation, including mountain snow,
into the region.  WPC probabilities indicate accumulations of 8
inches or more are likely across the higher elevations of the
northern Cascades Sunday into early Monday.  Impacts at the passes
appear to be more limited, however WPC probabilities show
accumulations of 4 inches or more likely at both Stevens and
Snoqualmie.

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

Pereira


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

-- A major winter storm will continue to impact coastal portions
of the Mid-Atlantic states and much of New England today.

-- Total snowfall accumulations greater than 12†are expected
along much of the Northeast coast with local maxima greater than
24†across eastern Massachusetts including the Boston metro.

-- Heavy snow rates of up to 2-4â€/hr and strong winds will
produce dangerous blizzard conditions along portions of the
Mid-Atlantic and New England coasts. Expect whiteout conditions
and nearly impossible travel at times. The strong to damaging
winds will lead to scattered power outages.

-- Significant coastal impacts are possible, including coastal
flooding and beach erosion.

-- Very cold temperatures will follow the storm with dangerous
wind chills tonight into Sunday morning.