FOUS11 KWBC 100834
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
334 AM EST Fri Jan 10 2025

Valid 12Z Fri Jan 10 2025 - 12Z Mon Jan 13 2025

...Mid-South/Southeast into the Mid-Atlantic...
Day 1-1.5...

...Major winter storm continues to progress eastward through the=20
Mid-South today with hazardous winter conditions into portions of=20
the Mid-Atlantic overnight...=20

A strongly positively-tilted longwave trough, with its axis back=20
into Mexico, will continue to help develop low pressure along the=20
Gulf Coast today on the southeast side of a 170kt jet. Gulf=20
moisture continues to stream northward into the Mid-South atop a=20
cold surface layer, yielding snow on the north side of the=20
expansive precipitation shield and a wintry mix of sleet and=20
freezing rain to the south (and plain rain toward the Gulf Coast).=20

Mid-level FGEN will drive moderate snow rates (~1"/hr at times)=20
over Tennessee this morning and early afternoon with a broader=20
shield of light snow to the north and northeast. Much of the region
from southeastern MO and across most of TN has at least moderate=20
probabilities (>40%) of seeing at least 4 inches of snow. To the=20
north, a general 1-3" of snow is forecast as additional northern=20
stream energy moves through the Midwest.=20

To the south, milder air aloft will move northward up and over the
cold surface layer, creating a mix of sleet and freezing rain over
northern AL/GA that will continue E/NE through SC into=20
central/eastern NC as the system evolves later tonight. Where the=20
surface cold air is most stubborn beneath the >0C air aloft,=20
several hours of ZR may accrete to near/over 0.25" esp over N GA.=20
There is a large area from northern AL to central NC where WPC=20
probabilities of at least 0.10" ice are >30% with an embedded area=20
of 20-50% probs for at least 0.25" of ice.=20

By this evening, upper trough will be stretched and elongated and=20
become dominated by the northern stream approaching the central=20
Appalachians. Low pressure will reform along the Carolina coast and
light northeastward overnight, spreading snow across interior NC=20
into VA with lighter snow extending northward into the Northeast.=20
Low pressure near Cape Fear 09Z Sat will quickly move northeastward
and deepen, with a potential modest band of snow on the northwest=20
side across southern/southeastern VA and the southern DelMarVa. WPC
Snowband Tool shows several members with ~1"/hr rates early Sat=20
morning (06-12Z) before the system finally scoots out to sea.=20
Though the probabilities for at least 4 inches are low (10-40%),=20
there is potential for some enhanced banding per a couple 00Z Hires
members.=20

Lastly, across the central Appalachians, orographic upslope will=20
help wring out several inches of snow over the higher terrain from=20
the Laurel Highlands southward down to the Smokey Mountains, where=20
WPC probabilities for at least 4 inches are >50%.=20



...Northwest to the Upper Midwest/Great Lakes...
Days 1-3...

Fairly sharp mid-level shortwave and sfc front will enter the=20
PacNW starting Friday morning with mostly higher elevation snow but
lowering snow levels (from ~4500 to ~3000ft) as the front moves=20
past the Cascades. The shortwave will move southeastward beneath a=20
weakening upper jet, but the combination of height falls and=20
upslope enhancement will maximize snow over the mountains, from the
Bitterroots to the Tetons and western MT today then into the=20
Big/Little Belts into the Bighorns and eventually the Black Hills=20
Saturday afternoon/evening as the stronger height falls move=20
through. WPC probabilities for at least 12 inches of snow D1-2 are=20
>50% above ~5000-6000ft or so (west to east) where two-day totals=20
could exceed 18-24 inches above 6000-7000ft (40-70% chance).=20
Farther south, with height falls digging into CO, areas in the=20
Rockies above ~8000ft have >50% chance of 8 inches of snow.

Additionally, on D2, an Alberta clipper will move into the=20
northern Plains/Upper Midwest with a swath of generally light snow=20
via WAA and FGEN on the northern side of an area of low pressure=20
moving through central ND into southern MN by late Sat/early Sun.=20
Amounts should generally be on the lighter side of a couple/few=20
inches, with moderate probabilities (40-70%) of at least 2 inches=20
of snow from northern ND eastward across northern MN. This low will
intensify during the Day Sunday when it moves over northern=20
Wisconsin and the U.P. before curling back to the northeast across=20
the U.P. and into Quebec by early Mon. A reinforcing upper level=20
low will rotate into northern MN by the end of the period, helping=20
to slow the progression of the sfc low over the U.P. or over Lake=20
Superior. This should act to enhanced low-level convergence over=20
the western U.P where several inches of snow are likely and WPC=20
probabilities for at least 4 inches of snow on D3 are 30-80%.=20
Southerly flow ahead of the front will tap some moisture off Lake=20
Michigan and help enhance totals on the southern side of the=20
eastern U.P. where WPC probabilities for at least 4 inches are >50%
(in a rather unusual setup).=20


Fracasso


...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_2.png__;!!DZ3fjg!4s1ryLm6VsyGK0LRFvb_6hsTzOrckqx-A4ltM_YB8oe3d=
9lQrmFQHIuYJ1yve7kwxpkHCnfKHDyQxduNUlOrJAXskVY$=20

$$

=3D =3D =3D
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