Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
406 PM EST Thu Dec 05 2019

Valid 00Z Fri Dec 06 2019 - 00Z Mon Dec 09 2019


Days 1-3...

...Northeast...
A fast-moving clipper system is expected to move from the upper
Great Lakes through the Northeast on Friday.  Although this system
is forecast to be a fast-mover, low-to-mid level frontogenesis is
expected to help accentuate precipitation rates and may be enough
to produce at least an inch or two across portions of Upstate New
York into western Massachusetts and southern Vermont.  Deepening
cold air and and northwest flow in wake of system is expected to
support a period of lake effect snow showers Friday evening that
will help bolster snow amounts southeast of the Lower Great Lakes.

...California...
As a deep cyclone continues to move gradually toward the coast,
heavy mountain snows developing initially over the Siskiyou
County/Mt.Shasta region of Northern California on Friday are
forecast to extend south along the Sierra late Friday into
weekend.  Deep onshore winds ahead of the system is expected to
support heavy precipitation with heavy snow likely along the
Sierra.  Snow levels are expected to begin around 6500ft before
lowering to around 5500ft on Sunday.  Widespread accumulations of
1-3 feet, with locally heavier totals can be expected by the end
of the weekend.

...Northern Rockies/Plains...
Low-to-mid level frontogenesis associated with a northern stream
trough digging south through western Canada into the U.S. will
help support light to moderate snows from the northern Rockies
into eastern Montana and western North Dakota on Sunday.

For Days 1-3, the probability of significant icing (0.25-inch) is
less than 10 percent.

Pereira