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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=20
 then into the Northeast Monday ***


...Southeast New Mexico/Guadalupe Mountains...=20
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=20
moisture from the Pacific will be directed eastward across northern
Mexico. Temperatures may be just cold enough even to the valley=20
floors for snow to accumulate, aided by an onset time early Monday=20
D2 with precipitation continuing through Monday night. Topographic=20
enhancement on the Guadalupe and southern Sacramento Mountains will
result in the highest probabilities for at least 4 inches of snow=20
-- generally 40-60%. To the east, light snow of a couple inches is=20
possible to the TX border where WPC probabilities of at least 2=20
inches are 20-50%.


...Great Lakes/Northeast...
Days 1-3... Maximum impact level from WSSI: Major to locally=20
Extreme

A vigorous closed low along the Montana/North Dakota border this=20
morning will dig southeastward into Iowa this evening as the upper=20
jet punches northeastward into the western Great Lakes. This will=20
set the stage for a rapidly-deepening/bombing cyclone the will move
across Lower Michigan tonight then into Canada on Monday. The=20
storm will have three main facets: synoptic snow via comma-=20
head/lake-enhancement from MN to the U.P. of Michigan, freezing=20
rain to its east (PA/Northeast US) in advance of a surface warm=20
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=20
the sfc low over MN/northern WI this afternoon along an inverted=20
surface trough and on the edge of the moisture gradient to the=20
southeast (where PW anomalies in the warm sector rise to >99th=20
percentile). Snow will expand and increase in intensity over=20
northern WI/U.P. of MI this evening, quickly becoming enhanced by=20
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=20
eastern U.P. of Michigan with sleet and freezing rain eventually=20
giving over to snow early Monday.

The low pressure will continue to deepen and briefly slow over=20
Lake Huron early Monday as the system becomes vertically stacked=20
and occludes (awaiting the mid-level low from the west). Peak=20
intensity should be reached Monday morning (mid 970s mb central=20
pressure) over Lake Huron or Georgian Bay with the warm conveyor=20
belt now completed wrapped up and around the low. Snowfall will=20
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=20
over much of the U.P. D1-2 probabilities of at least 6 inches of=20
snow are >50% from south central MN eastward across the northern=20
1/2 of WI and the northern 1/4 of Lower Michigan northward across=20
all of the U.P., where probabilities of at least 12 inches are=20
>70%. Probabilities for at least 24 inches of snow are >20% over=20
much of the northern and eastern U.P.=20

Well ahead of the main surface low, warm air advection will=20
overrun cold <32F surface temperatures from central PA this=20
afternoon through the Northeast tonight. Given snow is on the=20
ground through much of the region, the WAA aloft will have a tough=20
time reaching the surface, especially in normally sheltered=20
locations. Without a surface high to the north, temperatures will=20
have an easier time rising due to the freezing rain process itself,
but again counteracted by snow-covered ground which could act to=20
keep the surface warm front farther south. However, with such a=20
strong southerly flood of warm air, most guidance does show at=20
least a brief changeover to rain for nearly all of the Northeast=20
except for northern New England. Where the cold air holds on the=20
longest, ice could accumulate enough to be hazardous to trees=20
and/or power lines. WPC probabilities for at least 0.25" icing are=20
>50% over the Adirondacks and across much of central VT/NH into=20
southwestern Maine. In addition, probabilities for at least 0.50"=20
icing are 20-50% in these regions. Across northern Maine, the=20
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=20
northern Maine.=20

As the low moves through Ontario into Quebec, strong westerlies=20
will favor lake-effect snow across all Great Lakes, but focused=20
downwind of Lakes Michigan, Erie, and Ontario. Some multi-lake=20
connection and variable wind directions could support long-lived=20
single bands far inland away from the lake shores in concert with=20
breezy/windy conditions (i.e., blowing and drifting snow). In=20
addition, upslope flow into the central Appalachians will favor=20
some snow into the Laurel Highlands southward to eastern WV. WPC=20
probabilities for at least 8 inches of snow are >50% over northeast
Ohio and NW PA into the Chautauqua Ridge and south towns of=20
Buffalo as well as over central NYS around Syracuse northward to=20
Watertown and the Tug Hill Plateau. Some areas could see more than=20
12 inches of snow where bands maintain some residence time (>50%=20
chance).=20


Fracasso/Jackson


...Winter Storm Key Messages are in effect. Please see current=20
 Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late=
stKeyMessage_1.png__;!!DZ3fjg!5e4mWU_BbGp6NVxpLE-fbj3sgOfKqTOUhHgdpw2OEItZd=
d9WYVDF8OU5YYt0X2VOgRWMrOplBP1Qn3Te_cD8HaImg7I$=20



$$

=3D =3D =3D
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