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FOUS11 KWBC 152046
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
346 PM EST Thu Jan 15 2026

Valid 00Z Fri Jan 16 2026 - 00Z Mon Jan 19 2026

...Central and Northern Plains into the Great Lakes...
Days 1-3...

Persistent longwave trough across the eastern CONUS will=20
repeatedly re-load through the weekend in response to multiple=20
embedded shortwave troughs and accompanying vorticity lobes=20
swinging through.=20

The first of these will be exiting the Northeast into
Atlantic Canada D1 as a closed low with the accompanying trough
axis extending into the Southeast. Behind this trough and the
accompanying cold front, strong CAA in its wake will drive
continued lake effect snow (LES), especially east of Lakes Erie=20
and Ontario before shortwave ridging develops Friday aftn shutting
off the LES. WPC probabilities D1 are modest for 4+ inches of
additional snow, highest southeast of Lake Ontario where it reaches
30-50%.

Immediately in the wake of this first impulse, a second shortwave
will dig out of Saskatchewan and race S/SE, reaching the Mid-
Mississippi Valley by D2 before continuing to rotate E/NE into New
England on Sunday. This shortwave will push a power arctic cold
front southward beneath it, and a clipper-type low is also expected
to track to the southeast across the Great Lakes during this time.
While the accompanying synoptic snow through WAA is likely to be
minimal, renewed CAA across the Lakes should result in additional
LES, with more widespread coverage as cold N/NW flow envelops the
entire region. A third shortwave is expected to cross into the
Great Lakes on Sunday with subsequent ascent and moisture leading=20
to more snowfall, but additional accumulations before 00Z Monday
should be minor. Before that time, however, 3-day snowfall
probabilities from WPC indicate a high risk (>70% chance) for at=20
least 8 inches across the western U.P. and much of the western=20
shore of the L.P. where locally 1-2 feet is possible. Lesser=20
amounts are expected east of Lake Ontario, but still modest=20
accumulations exceeding 8 inches have a low chance (10-30%) of=20
occurring.

In addition to the LES, the arctic cold front and post-frontal CAA
will provide sufficient ascent for widespread snow showers and
possible snow squalls across the Northern Plains, Upper Midwest,
and potentially into parts of the Great Lakes/Ohio Valley. This
will begin tonight across the Dakotas, and then persist through
Friday night while expanding southeast. While the setup does not
appear extremely favorable for strong snow squalls, linear bands
aligned perpendicular to the front within a region of elevated
0-2km fgen, increasing low-level moisture, and steepening lapse
rates where winds at the top of the PBL exceed 50 kts in some
areas, will support widespread snow showers (or squalls) with brief
heavy snow rates and gusty winds. While snowfall accumulations
across this region accompanying these squalls will be minimal, when
snow occurs it will fall heavily, and when combined with the strong
winds will create periodic near zero visibility and dangerous
driving. The alignment of these snow showers/squalls will also
support multiple rounds in some areas through D2.

Key Messages have been issued for these snow squalls, and they are
linked at the bottom of this discussion.


...Ohio Valley, Mid-Atlantic, and Northeast...=20
Days 1-3...

Progressive flow within a reloading and persistent mid-level
longwave trough will create active winter weather across the area
through the weekend.

For D1, a low pressure system rapidly exiting into Atlantic Canada
will leave residual moisture and ascent across primarily Maine
where a theta-e ridge continues to pivot briefly tonight, with
increasing NW flow/upslope ascent occurring as the low pulls away.
Forecast soundings indicate a rapid drying of the DGZ tonight so
any moderate snow should wane quickly by Friday morning, but WPC
probabilities indicate a low risk (10-30%) for an additional 4+
inches of snow in northern ME.

Thereafter, the mid-level trough begins to re-amplify in response
to a shortwave diving through the Great Lakes and elongating into
the Ohio Valley and Central Plains. This evolution will drive an
arctic cold front sharply east, reaching the Mid-Atlantic states by
the end of D2 /00Z Sunday/. A shortwave downstream of this front
may help develop a wave of low pressure which will bring some light
to moderate snowfall to New England, although WPC probabilities for
more than 2" of snow D2 are only around 30%, highest in the higher
elevations of the Catskills and Berkshires. More substantial
snowfall is likely through lift along the front, followed by
impressive upslope snow into the Central Appalachians, as well as
parts of western PA. Steepening lapse rates will keep the DGZ
relatively shallow, but sufficient ascent into the moistened column
will result in periods of moderate to heavy snowfall which may
accumulate to more than 4 inches in parts of WV and PA as reflected
by WPC probabilities reaching 30-50%.

Then during D3 /00Z Sunday to 00Z Monday/ an elongated lobe of
vorticity will swing into New England, while a secondary and
sharpening shortwave dives into the primary longwave trough across
the Mississippi Valley. While the lead impulse may cause some light
snow across Maine (WPC probabilities for 4+ inches 10-30%), the
more challenging and bigger concern will be what happens with
moisture spreading northward from the Southeast the latter half of
D3. While uncertainty is significant, there is at least modest
confidence that light precipitation will spread far enough
northwest to bring snowfall to parts of the Mid-Atlantic coast from
eastern VA through coastal NJ, and potentially onto Long Island and
Cape Cod. Current WPC probabilities are modest (30-50% for 1"), but
trends will need to be monitored as the system develops in the next
few days.


...Southeast...
Day 3...

A complex forecast scenario is evolving for portions of the
Southeast beginning around 00Z Sunday and persisting through D3. An
arctic cold front will push into the area Saturday and then=20
progress rapidly to the Atlantic Coast by Sunday morning. As this
front pushes east, a sharpening upper shortwave trough will rotate
near the Gulf Coast, potentially taking on a negative tilt late in
the forecast period (although there is a lot of uncertainty into
the amplitude of this feature). At the same time, a downstream jet
streak will amplify to become powerful over the Mid-Atlantic and
Northeast, leading to weak surface cyclogenesis along the Gulf
Coast. As this wave develops, moisture will spread northward, and
while the column will initially be too warm for wintry
precipitation, rapid cooling behind the front will allow for a
changeover from rain to snow.=20

The speed at which this occurs, as well as how much moisture can=20
remain in the column after transition, will play the most important
role into any possible snowfall accumulations. The GFS continues=20
to be the most robust with the transition and available moisture=20
for snow, while the EC and CMC are weaker and drier. Evaluation of=20
the D3 clusters suggests that both the CMC and GFS ensembles are=20
under-dispersive (with the CMC members nearly uniformly deeper=20
with the trough, while the GFS members are nearly uniformly faster=20
at 500mb), suggesting the EC members and their variety of=20
solutions results in a more accurate solutions via the ECENS mean.
While there is still a lot of uncertainty, confidence is increasing
for at least mixed rain/snow from the Florida Panhandle northeast
through southeast Virginia. While the threat for significant
accumulations appears small, and WSE plumes only have a handful of
members producing >1" of snow, the WPC probabilities have increased
and suggest a 10-30% chance for 1" of snow from southern AL through
the NC Piedmont and into the coastal Mid-Atlantic states. Forecast
changes are almost certain, so those potentially impacted should
remain apprised of the latest forecast through the next few days.


Weiss


...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!6RNjUAou4g17Px_u1pNFlRzORKhcuzmoTm4odAbI2R7Ol=
g8xKox0NZQc9EVJ7SQwiAS7NX09bAHxt-zgZW50whtt9wE$=20



$$

=3D =3D =3D
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