Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
153 PM EST Tue Feb 19 2019

Valid 00Z Wed Feb 20 2019 - 00Z Sat Feb 23 2019


...The West...
A northern stream trough will continue to shift inland across the
West Coast today with moisture diminishing as it pushes inland
across the Intermountain West from both topographical effects as
well as shortwave ridging behind the trough axis ahead of the next
trough descending from a sprawling Gulf of Alaska low. Low to mid
probabilities for four inches are across the west in Day 1; from
the Four Corners area (under the trough) across the Great Basin
with snow ending today over the Sierra Nevada.

Heavy precipitation will redevelop across the Northwest tonight as
the leading edge of potent atmospheric river reaches WA/OR in a
strong jet south of a Gulf of Alaska low. Snow levels will greatly
increase over OR tonight into Tuesday along the AR axis with lower
levels (and much greater snow) in WA for Day 2. Heavy snow with
multiple feet of accumulation is on tap for the Washington
Cascades with high WPC probabilities for 8 inches over terrain of
ID/MT.

Snows are expected to continue into Wednesday before waning that
day as a strong upper ridge begins to build along the West Coast.
The active pattern continues, however, with the next system
approaching western WA Wednesday night. Copious moisture is also
anticipated with this low/cold front late in the work week.


...Northeast U.S...
The southern stream low presently centered south of New England
will continue to lift northeast and track along/just off Nova
Scotia today. A northern stream trough currently over Ontario will
dig across New England today and phase with the southern stream
low prolonging snow over ME through tonight. Moderately high
probabilities for six inches exist for northeastern ME with the
bulk of the snow occurring through this evening.

Jackson