FOUS11 KWBC 280724
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
224 AM EST Sun Dec 28 2025

Valid 12Z Sun Dec 28 2025 - 12Z Wed Dec 31 2025

*** Major Winter Storm for the Upper Midwest/Great Lakes tonight
then into the Northeast Monday ***

...Great Lakes/Northeast... Days 1-3...
Maximum impact level from WSSI: Major to locally Extreme

A vigorous closed low along the Montana/North Dakota border this
morning will dig southeastward into Iowa this evening as the upper
jet punches northeastward into the western Great Lakes. This will
set the stage for a rapidly-deepening/bombing cyclone the will move
across Lower Michigan tonight then into Canada on Monday. The
storm will have three main facets: synoptic snow via comma- head/lake-enhancement from MN to the U.P. of Michigan, freezing
rain to its east (PA/Northeast US) in advance of a surface warm
front, and lake- effect snow as the system departs across all Great Lakes.

Snow associated with the approaching cold front from the west will
merge into the developing comma-head snowfall to the northwest of
the sfc low over MN/northern WI this afternoon along an inverted
surface trough and on the edge of the moisture gradient to the
southeast (where PW anomalies in the warm sector rise to >99th
percentile). Snow will expand and increase in intensity over
northern WI/U.P. of MI this evening, quickly becoming enhanced by
Lake Superior as cyclonic flow rapidly intensifies. Just east/ahead
of the low center will be a wintry mix over the northern L.P. and
eastern U.P. of Michigan with sleet and freezing rain eventually
giving over to snow early Monday.

The low pressure will continue to deepen and briefly slow over
Lake Huron early Monday as the system becomes vertically stacked
and occludes (awaiting the mid-level low from the west). Peak
intensity should be reached Monday morning (mid 970s mb central
pressure) over Lake Huron or Georgian Bay with the warm conveyor
belt now completed wrapped up and around the low. Snowfall will
maximize over the northern shore of the U.P. where powerful onshore
flow pivots as the low passes. Locally, 1-2ft of snow is likely
over much of the U.P. D1-2 probabilities of at least 6 inches of
snow are >50% from south central MN eastward across the northern
1/2 of WI and the northern 1/4 of Lower Michigan northward across
all of the U.P., where probabilities of at least 12 inches are

70%. Probabilities for at least 24 inches of snow are >20% over

much of the northern and eastern U.P.

Well ahead of the main surface low, warm air advection will
overrun cold <32F surface temperatures from central PA this
afternoon through the Northeast tonight. Given snow is on the
ground through much of the region, the WAA aloft will have a tough
time reaching the surface, especially in normally sheltered
locations. Without a surface high to the north, temperatures will
have an easier time rising due to the freezing rain process itself,
but again counteracted by snow-covered ground which could act to
keep the surface warm front farther south. However, with such a
strong southerly flood of warm air, most guidance does show at
least a brief changeover to rain for nearly all of the Northeast
except for northern New England. Where the cold air holds on the
longest, ice could accumulate enough to be hazardous to trees
and/or power lines. WPC probabilities for at least 0.25" icing are

50% over the Adirondacks and across much of central VT/NH into

southwestern Maine. In addition, probabilities for at least 0.50"
icing are 20-50% in these regions. Across northern Maine, the
column may be stay entirely below freezing near the Canadian border
as a triple point low may help prevent a southerly wind component.
WPC probabilities for at least 4 inches of snow are >30% over far
northern Maine.

As the low moves through Ontario into Quebec, strong westerlies
will favor lake-effect snow across all Great Lakes, but focused
downwind of Lakes Michigan, Erie, and Ontario. Some multi-lake
connection and variable wind directions could support long-lived
single bands far inland away from the lake shores in concert with
breezy/windy conditions (i.e., blowing and drifting snow). In
addition, upslope flow into the central Appalachians will favor
some snow into the Laurel Highlands southward to eastern WV. WPC
probabilities for at least 8 inches of snow are >50% over northeast
Ohio and NW PA into the Chautauqua Ridge and south towns of
Buffalo as well as over central NYS around Syracuse northward to
Watertown and the Tug Hill Plateau. Some areas could see more than
12 inches of snow where bands maintain some residence time (>50% chance).

...Southeast New Mexico/Guadalupe Mountains... Day 2...
Maximum impact level from WSSI: Moderate

A cold front racing southward from the CO Rockies today will leave
behind a sfc-700mb baroclinic zone along the Rio Grande as
moisture from the Pacific will be directed eastward across northern
Mexico. Temperatures may be just cold enough even to the valley
floors for snow to accumulate, aided by an onset time early Monday
D2 with precipitation continuing through Monday night. Topographic
enhancement on the Guadalupe and southern Sacramento Mountains will
result in the highest probabilities for at least 4 inches of snow
-- generally 40-60%. To the east, light snow of a couple inches is
possible to the TX border where WPC probabilities of at least 2
inches are 20-50%.

Fracasso/Jackson

...Winter Storm Key Messages are in effect. Please see current
Key Messages below...

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png

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* Origin: Capitol City Online (21:1/175)