Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
355 AM EDT Wed Apr 03 2019

Valid 12Z Wed Apr 03 2019 - 12Z Sat Apr 06 2019

...Northeast...
Days 1 & 3...

Impressive surface low will continue to move northeast into the
Canadian Maritimes today. As this low pulls away to the northeast
by this evening, it will be followed quickly by a northern stream
shortwave racing across northern New England and offshore tonight.
These features together will produce light to moderate snow,
focused across central and northern Maine where the airmass will
remain cold enough for snow. A sharp west-east gradient in
moisture is likely, so WPC probabilities for 4 inches are confined
to the Maine/New Brunswick, Canada border.

A second system will approach Friday morning with precipitation
spreading across the Northeast on WAA and weak height falls. While
initially the column will be cold enough for snow, the WAA will
drive a warm nose through the area causing p-type to transition to
light freezing rain and then rain. The best chance for
accumulating snow will be in the high terrain of the Adirondacks
and Northern New England, where WPC probabilities are moderate for
4 inches. Although freezing rain accretion should be light, WPC
probabilities have increased and now feature a slight risk for 0.1
inches from northern PA into eastern NY and central New England.


...Western U.S...
Days 1-3...

A weakening mid-level trough scooting eastward into the Plains
will bring lingering light snows to the Rockies today, but WPC
probabilities are modest for 4 inches, highest in the San Juans
and NW Wyoming ranges.

A more significant system will approach the Oregon coast on
Friday, with significant moist advection on Pacific Jet energy
rotating onshore south and east of this feature. Although flow
into the west will be mostly zonal as the low shifts northeast
into western Canada, keeping snow levels high, the persistent
nature of the anomalous moisture will produce widespread snow
across the West. Snow levels above 6000 ft outside of the Pacific
NW will keep the heaviest accumulations in the highest terrain of
the Sierra, Shasta/Trinity/Siskiyou, and OR Cascades where WPC
probabilities are high for 8 inches. Elsewhere, a moderate risk
for 4 inches exists from the WA Cascades east into the Northern
Rockies, and southward into Utah and CO.


Weiss