Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
415 AM EST Fri Mar 06 2020

Valid 12Z Fri Mar 06 2020 - 12Z Mon Mar 09 2020


Days 1-3...

...Northeast...

A closed low/upper trough moving across the Great Lakes
interacting with southern stream energy lifting along the Mid
Atlantic coast will support a rapidly deepening surface cyclone
tracking Northeast off of the Mid Atlantic coast Friday into early
Saturday.  While the system is expected to track far enough east
to preclude heavy snows along much of the Eastern Seaboard, the
overnight models are showing a signal for mesoscale banding and
heavier QPF a little farther north across southeastern
Massachusetts Friday night and Saturday morning.  While boundary
layer temperatures are expected to be marginal at the onset, heavy
precipitation may offset these temperatures - raising the
potential for impactful snow accumulations across Nantucket and
Cape Cod Saturday morning.

Across the interior Northeast, expect mainly light amounts across
New York and Pennsylvania associated with the upper trough.  As
the system moves east of the Great Lakes, strong northerly flow on
the backside of the system is expected to produce some
lake-enhanced snow showers south of Erie and Ontario on Friday
before high pressure builds across the region early Saturday.

...Central and southern Appalachians...
Strong, cyclonic upslope flow with embedded energy aloft will
support snow showers, with locally heavy amounts possible in the
upslope regions of the Alleghenies and southern Blue Ridge through
Friday.

...Western U.S....
Cold front associated with an offshore upper trough is forecast to
slow over the Northwest on Friday before advancing farther south
and east as energy moving through the base of the trough pivots
toward the coast late Friday into Saturday.  This will bring some
light to moderate snows south from the Cascades into the Sierra on
Saturday.  Meanwhile, post-frontal upslope flow behind a front
settling south from Canada, enhanced by a low level wave dropping
southeast across Montana, will support moderate to heavy snows
along the northwestern Montana ranges on Saturday.

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

Pereira