Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
309 AM EST Tue Nov 30 2021

Valid 12Z Tue Nov 30 2021 - 12Z Fri Dec 03 2021


...Great Lakes/Northeast...
Days 1-3...
Ongoing clipper system moving through the Great Lakes and
Northeast today will continue moving east, reaching the Northeast
later tonight. The initial frontogenetical band of precipitation
will track across central PA this morning then begin to dissipate
as it approaches interior New York. Significant heavy snowfall
isn't expected across PA this morning and the 2" WPC probabilities
show only a small/localized area of moderate to high
probabilities. Quick on the heels of this system is a northerly
clipper that will pass through the Great Lakes later today and
reach northern New York and northern VT/NH tonight. This will
bring some warm advection snows to the higher elevations of the
Tug Hill and Adirondacks tonight as well as a period of heavier
lake effect snow off Lake Erie and Ontario. The Tug Hill has the
highest snowfall accumulation probabilities, with moderate /40-50
percent/ chances for 4" through 12Z Wednesday.

In the fast quasi-zonal flow, another quick moving clipper system
will track across central Canada and just north of the Great Lakes
Wednesday into Thursday. Warm advection precipitation Wednesday
morning may be a wintry mix of snow/rain/freezing rain across
portions of the Upper Midwest before changing to all rain. The
system is forecast to turn the east, tracking across southern
Ontario and Quebec on Thursday.  Warm advection precipitation is
forecast to spread across the Northeast with a wintry mix at the
onset for the interior, before a change to rain for most
locations. However, thermal profiles may support mostly snow
across the Adirondacks and the northern VT/NH mountains, with WPC
probabilities indicating a moderate threat /40 percent/ of
exceeding 2 inches during the day 3 period.


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

Taylor