032
FOUS11 KWBC 081953
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
253 PM EST Sat Nov 8 2025

Valid 00Z Sun Nov 09 2025 - 00Z Wed Nov 12 2025

...Great Lakes, Northeast, and central/southern Appalachians...
Days 1-3...

Shortwave trough/vort max near western IA this afternoon is
expected to swings east across the Midwest tonight and into the
Lower Great Lakes by Sunday as it begins to turn northeast around a
deeper upper low centered over southern Ontario. Ongoing snow
banding over central/northern IA ahead of this wave also shifts
east on the northern periphery of a surface low. Marginal surface
temperatures should limit snowfall somewhat outside of more intense
snow bands and rates approaching 1"/hr. These rates and light
accumulations become more likely by Sunday morning across northern
IN, northwest OH, and southern MI as fgen increases and overlaps
the DGZ. This is highlighted nicely within the 12z HREF. Day 1 WPC
probabilities for >4" are around 20-30% from northern IN to
southern MI and northwest OH. Additionally, WAA ahead of this
deepening low across northern New England and Upstate NY will
overspread precipitation into subfreezing surface temperatures,
leading to some mixed ptype concerns. Snowfall amounts should
remain mostly light and most likely to occur after the system has
exited the region on Mon-Tues morning. However, some light freezing
rain could be possible across northern NY, including the
Adirondacks and favorable low elevations along the St. Lawrence
where low-level cold air may remain locked in place on the
northwest side of the low system. WPC probabilities for at least
0.1" of ice accretion are between 10-40% and also include the White
Mts of NH and ME.


...Lake Effect/Enhanced Snow tonight through Tuesday...
A reinforcing shortwave trough rounding a deep low shifting south
from Hudson Bay is set to cross the Upper Midwest tonight with a
deep second lobe developing over Michigan Sunday that swings south
before tracking over the Interior Northeast Monday night will
provide the likelihood for the first major lake effect and
Appalachian upslope snow event of the season. This reinforcing
trough importantly slows the progress of the surface trough along
the Northeast coast Sunday which prolongs the following flow over
the Great Lakes for lake effect/enhanced snow tonight of Lake
Superior shifting through all the Great Lakes before easing off
Lake Ontario on Tuesday. Strong CAA brings a winter-like airmass to
the region, headlined by 850mb temperatures between negative 10
and 12 degrees C. This cold air (near or below the 10th
climatological percentile) 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 possible 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 tonight through
Monday, Lake Michigan Sunday night through Monday, Lakes Huron and
Erie Sunday night through Monday night, and Lake Ontario Monday
night/Tuesday. Forecast remains uncertain around the Chicago metro
as the north-south Lake Michigan band remains mostly aimed at
northwest IN besides on Monday when the deep upper low passes from
eastern WI into northern IL. This may tug the lake effect band
westward into northeast IL for a period, where snowfall rates
remain impressive and around 2"/hr. Regardless, localized totals
over 1 foot are possible (30-50%) in northwest IN depending on how
long the single Lake Michigan snowband can remain in tact. Days
1-3 WPC probabilities for >8" are over 60-80% in the Huron Mtns of
the U.P. of MI and for portions of the western L.P. shoreline and
all of the Indiana shoreline. Additional 40-60% WPC probabilities
for >8" exist along the shoreline of Lake Erie from northeast OH
into northwest PA and far western NY.

Cold upslope northwesterly flow and a moist fetch from Lake
Michigan will also cause upslope snow showers for the
Central/Southern Appalachians Sunday night through Monday night
with Days 2-3 WPC probabilities for >6" 40-70%.



Snell/Jackson



$$