Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
402 AM EST Thu Nov 07 2019

Valid 12Z Thu Nov 07 2019 - 12Z Sun Nov 10 2019


Days 1-2...

...Northeast...
A wave of low pressure moving along a southeastward pushing cold
front will spread precipitation across the Mid-Atlantic and
Northeast. This setup will produce an environment favorable for
rain turning to snow across much of the area, with snow more
likely in the higher elevations of Northern New England. As the
upper trough driving this system sharpens and tilts negatively,
the surface low will swing northeast across eastern New England,
but with only a modestly amplified system, the cold air will be
chasing the precipitation, and the low will skirt quickly away.
Despite the rapid motion, the combination of enhanced 700mb RH,
mid-level height falls, and at least weakly coupled jet streaks
will produce a long period of moderate ascent from Thursday into
Friday. WPC probabilities for 4 inches of snowfall are highest in
the Adirondacks, Greens, and White mountain ranges, where a
moderate risk exists. There are some low end probabilities for 6+
inches as well, highest in the Presidential Range of NH. Some
light snow may spread down to the immediate coast of Maine and
towards the suburbs of Boston, but WPC probabilities this far east
are low even for 1 inch, and is most likely as the cold air floods
southward behind the departing low.

...Great Lakes...
Significant Lake Effect snowfall is likely in the favorable NW
flow locations in the U.P. and northern L.P. of Michigan. The
combination of strong CAA and slowly veering winds across the
still very warm lakes will create an environment favorable for
heavy bands of LES, and soundings depict a fully saturated DGZ
with mixing depths over 8000 ft. Moderate to at times heavy
snowfall is possible in the eastern U.P., as well as in NW L.P.
where combined fetch lengths reach across Superior and Michigan.
Although multi-bands are possible which creates less confidence in
a focused region of heaviest snow, WPC probabilities indicate a
high chance for 8 inches east of Marquette, MI, with slightly
lower probabilities near Traverse City in the L.P. 

The probability of significant icing (0.25 inch) is less than 10
percent.

Day 3...

...Northern Rockies...
A wave of low pressure and associated cold front will drop
southward from Canada into the Northern Plains during D3.
Increasing mid-level RH combined with a digging jet streak and
low-level upslope flow will spread snowfall into portions of ND
and MT. While much of the forcing and snowfall may occur just
beyond this D3 period, WPC probabilities indicate a low chance for
4 inches late Saturday in the vicinity of Glacier NP.

The probability of significant icing (0.25 inch) is less than 10
percent.

Weiss