Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
402 AM EST Wed Nov 06 2019

Valid 12Z Wed Nov 06 2019 - 12Z Sat Nov 09 2019


Day 1-3...

...Midwest/Great Lakes...
As a jet maxima crosses northern WI into the UP of MI today into
this evening, and then south across WI and MI tonight, lift in the
favored right entrance region combines with low-to-mid level
frontogenesis to support bands of snow from southern WI across
central Michigan.  Several inches are expected, particularly with
lake enhancement near Lake MI.
Day 1 probabilities remain greater than 40 percent for
accumulations of 4 inches or more across portions of southern
Wisconsin and west central MI.  With winds nearly parallel to the
Lake Superior shoreline, snow showers remain close to the
shoreline in the eastern UP of MI. Snow showers develop along the
western Superior shoreline as flow veers to become northwest by
Thu morning.

On Day 2, the upper trough comes overhead along with the core of
cold airmass in the upper lakes.
Drier air advects over the western UP of MI, so the longer
duration snow showers and resultant higher amounts focus along the
shore areas of the eastern UP of MI and into northwest lower MI,
where stronger leeshore convergence persists near Traverse Bay.   

On Day 3, the rapid change of wind directions reduces duration of
snow showers at any one location, leading to lighter amounts as
drier air moves into the region later Friday.  The next front
approaches Fri night,w hen snow showers redevelop over the UP of
MI as the front arrives. The limited duration of snow shower
activity leads to light amounts until lake effect snow redevelops
early Sat.


Days 2-3...

...Northeast...
Light snow is expected to spread east of the Great Lakes into
Upstate New York and New England, but with only minor
accumulations expected through early Thursday.  Upstream energy
diving into the base of the trough is forecast to sharpen the
trough over the Great Lakes - leading to low pressure developing
over coastal New England and moving north. Snow is expected to
develop within the mid level deformation axis moving across
northern New York and northern New England. 

This will mean rain for the major cites of the Northeast, but
moderate to locally heavy snowfall for the Adirondacks, Green
Mountains, White Mountains, and central Maine.   The models have
reduced low position timing differences, with the GFS now
clustering better with the NAM and ECMWF low tracks. The progress
of the low has it moving away from northern New England Fri with
snow winding down in Maine and residual snow showers in the
mountains of northern VT and NH where upslope flow aids lift.

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

Petersen