Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
309 PM EST Mon Dec 07 2020

Valid 00Z Tue Dec 08 2020 - 00Z Fri Dec 11 2020

...Pacific Northwest...
Days 1-3...

A zonal jet streak currently over BC/Alberta will continue to
allow Pacific moisture to stream into WA through tonight. While
snow levels are rather high (7 to 8 kft), lingering cold air in
the lee of the Cascades will only slowly retreat. Therefore, there
is a 20 percent chance for a tenth inch of freezing rain on Day 1
in north-central WA.

A shortwave approaches Tuesday night with snow levels decreasing
through Wednesday. Then the next shortwave approaches on Thursday.
Day 2/3 snow probabilities for 4 or more inches are 20 to 30
percent for the WA Cascades and ranges near Glacier NP.


...New York...
Days 2/3...

A shortwave trough on the leading edge of a jet streak rounding
the broad ridge over the western US pushes southeast across the
Northeast CONUS late Tuesday night into Wednesday. Some lake
enhanced snow may be moderate at times Tuesday night with some
lake effect snow Wednesday. Conditions are marginal thermally for
snow with most or all of the saturated layer below the dendritic
snow growth zone. Areas with greater lift, such as the Tug Hill
Plateau of NY do have a 30 percent chance of 4 or more inches on
Day 2.


...Southwest...
Day 3...

A cutoff low that shifted south off the southern CA coast today
will eject east Wednesday night, crossing AZ/NM on Thursday. ample
Pacific moisture is forecast and snow levels lowering to about
7500ft under the trough will allow some high elevation snows for
the Highest Mogollon Rim and White Mtns of AZ into NM. As of now
there are low probabilities for 4 or more inches for the highest
portions of the White Mtns on Day 3.


Jackson