209
FOUS11 KWBC 092037
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
337 PM EST Sun Nov 9 2025

Valid 00Z Mon Nov 10 2025 - 00Z Thu Nov 13 2025

...Great Lakes to Interior Northeast and Appalachians...
Days 1-2...

Leading shortwave impulse/vort max lifts northward over Lake
Ontario tonight as an area of low pressure reloads on Monday over
New England as the deep upper low swings across the Ohio Valley.
This setup will provide warm air advection mixed ptype into
northern New England, the northern Adirondacks, and St.Lawrence
river valley through tonight before cold air advection returns to
the region Monday into Tuesday. Light freezing rain is expected in
at least pockets from the Tug Hill through the Adirondacks and
north as well as the White Mtns of NH/ME. WPC probabilities for
>0.1" ice accretion are between 30-50%% in northern NY and closer
to 30% for the White Mtns.

...Lake Effect/Enhanced Snow through Tuesday...
Deepening upper-low drops southward from the Great Lakes tonight to
the southern/central Appalachians Monday night, with heights
dropping into record levels for early-mid November. This will lead
to the first major lake effect and Appalachian upslope snow event
of the season as bitter cold Canadian air rushes over the warm
Great Lakes. The pivoting and depth of the developing strong upper
low over the Great Lakes region will prolong the cold air advection
flow and thus lake effect/enhanced snow from Lake Superior through
Monday with single banding likely off Lake Michigan tonight/Monday
with Huron/Erie/Ontario LES late tonight through Tuesday.
Favorable QPF spreads through all the Great Lakes before easing off
Lake Ontario on Tuesday.

The cold airmass, headlined by 850mb temperatures between negative
10 and 12 degrees C over the warm Great Lakes (temperatures of +10
to +15C) will result in an impressive convective environment with
model soundings indicating steep lapse rates and deep mixing
heights to near or above 700mb. Given lake temp and 850mb air temp
delta Ts of 20 to 30C, the environment will be rather supportive
for lake effect/enhanced snow production and likely periods of
thundersnow.

North-northwest to northerly surface winds along with increasingly
unidirectional winds aloft will act on the instability and support
the development of a few prominent north-south lake effect snow
bands, particularly downwind of Lake Superior through Monday, Lake
Michigan tonight through Monday, Lakes Huron and Erie late tonight
through Monday night, and Lake Ontario Monday night/Tuesday.
Decent confidence in heavy banding spreading west into the Chicago
metro this evening as CAMs develop a mesolow over southern Lake
Michigan and help enhance the intense snow rates around 2-3"/hr
along the western shores before drifting back east through Monday
morning. Localized totals over 1 foot are possible (10-20%) in
northwest IN depending on how long the single Lake Michigan
snowband can remain in tact. Here, major impacts are possible due
to very intense snowfall rates and extend into the highly
populated region of northwest IL tonight. In addition, cold
upslope northwesterly flow and a moist fetch from Lake Michigan
will also cause upslope snow showers for the Central/Southern
Appalachians tonight through Monday night with Days 1-2 WPC
probabilities for >6" 40-70%. Days 1-2 snow WPC probabilities for
>8" are 30-60% in northeast IL, northwest IN, the central
Appalachians/Alleghenies, and southern Appalachian crest.
Additional 50-80% Day 2 WPC probabilities for >8" exist along the
shoreline of Lake Erie from northwest PA into far western NY and
along the southern shoreline of Lake Ontario between Wayne and
Oswego counties. As always the case with lake effect snow, amounts
and impacts could drastically differ over the span of tens of miles
depending on where snowbands situate.



Snell/Jackson





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