Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
406 AM EST Fri Feb 25 2022

Valid 12Z Fri Feb 25 2022 - 12Z Mon Feb 28 2022

...Mid-Atlantic and New England...
Day 1...

Shortwave moving through the eastern Great Lakes early Day 1 will
carry the final stage of this multi-day/multi-faceted winter storm
through the Mid-Atlantic/Northeast before moving offshore tonight.
Surface low pressure on the west side of the Appalachians will
move through western PA into NY and weakens this morning as the
wave along the warm front offshore the NY Bight strengthens and
passes near the 40/70 benchmark early this afternoon, becoming the
dominant area of low pressure. This will lead to a progressive end
to the precipitation by Saturday morning. However, intense
frontogenesis and broad upper diffluence will promote heavy snow
rates this morning across northern NY into central New England
(1-2"/hr) through a modest DGZ which will add up to over 6 inches
in a swath from west to east along and north of a ART-ALB-BOS
line. Easterly flow in the lower levels will accent the terrain in
N-S bands of heavier/lighter amounts along the Greens/Whites and
through the valley locations. South of there, warm nose will
maintain a mixed precip zone across the Southern Tier through PA
into MD with predominately freezing rain and a fair amount of
sleet possible to the east into eastern/northeastern PA and
northern NJ. Depth of cold air and strength of the warm nose aloft
have been tough to forecast for the life of the system back to the
southern Plains, but the NAM has generally continued to fair well.
WPC probabilities for at least 8 inches of snow are moderate to
high over northeastern NY and across much of VT/NH into the Maine
Midcoast. Farther south, WPC probabilities for at least 0.10" ice
are generally less than 20 percent near the Poconos into western
CT.

...Pacific Northwest...
Days 2-3...

A pair of shortwaves in the northeastern Pacific will stream
northeastward into WA/OR late Sat into early Sun and the second
into Vancouver late Sun into early Mon. This will take a cold
front into western WA Day 2 with a plume of moisture (+1 to +2.0
sigma) on southerly flow but will weaken quickly in advance of the
next front. That system should still be offshore by the end of day
3, with another surge in moisture (PW values over +2.5 sigma along
the WA/OR coast by 12Z Mon). Snow levels will rise in advance of
the lead front but linger around 2000-3000ft along the Cascades
with several inches likely at pass levels around that altitude.
Second front will bring in even milder air with snow levels rising
to near 4000-5000ft on the west side of the Cascades Day 3.


Fracasso



Key Messages:

 - The multi-day winter storm will move through the Northeast
today with heavy snow to the north and an area of mixed
precipitation to the south.

 - A swath of 6-12 inches of snow is expected over much of
central/northern New York into central New England. Heavy snow
rates of 1-2 inches per hour will make travel difficult into the
early afternoon.

 - Additional ice accumulations around 0.10 inch are expected over
eastern Pennsylvania eastward into Connecticut this morning.
Travel will be treacherous on untreated surfaces.