Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
338 AM EST Sun Nov 17 2019

Valid 12Z Sun Nov 17 2019 - 12Z Wed Nov 20 2019

...Northeast...
Days 1-3...

Southern stream low pressure currently off the southeast coast
will be drawn north ahead of a neutrally tilted northern stream
trough currently over the northern Great Plains. Precipitation
from this system will reach the Northeast coast tonight. Warm air
aloft, with subfreezing boundary layer temperatures will support a
wintry mix over much of New England and upstate New York as the
low passes to the east of Maine through Monday night. Heaviest ice
accretion is expected to center along the Green Mountains of
Vermont and across northern Maine, where WPC probabilities
indicate a 40 to 60 percent risk for for storm total ice
accumulations of a 0.25-inch or more. Wrap around snow as the
northern stream trough comes through is expected Tuesday with far
northern New England and the Adirondacks having a 40 to 60 percent
chance for four inches of snow for Day 2.5.


...Northwest...
Days 2 and 3...
A progressive closed low moves east across WA/OR Monday night,
reaching MT by Tuesday morning. Deep Pacific moisture will result
in high snow levels at the for the Pacific Northwest, but height
falls bring the snow level down to around 4000ft on Tuesday. A
surface low is trackable across the northwest with enhancement
expected in the lee of the northern Rockies in central MT. This
prolongs upslope flow for eastern slopes of the Rockies in MT and
promotes higher snow totals in areas such as Glacier NP where the
Day 3 probabilities are 30 to 50 percent for a foot of snow.

Jackson