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FOUS11 KWBC 132020
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
320 PM EST Tue Jan 13 2026

Valid 00Z Wed Jan 14 2026 - 00Z Sat Jan 17 2026


...Northern Plains through the Northeast, and the Appalachians...
Days 1-3...

A trough across the eastern CONUS will amplify impressively and
periodically re-load through the period as repeated shortwaves
intensify and drop southeast from Canada. The core of this trough
will deepen most impressively to reach the Gulf Coast Thursday aftn
(NAEFS 500mb heights below the 1st percentile within the CFSR
climatology), but remain below the 10th percentile with secondary
amplification occurring on Friday.

Within this trough, and really the driving factor behind amplifying
this trough, will be repeating shortwaves digging out of Canada and
racing southeast through the flow. The first of these will move
from Minnesota to the Ohio Valley D1, with a secondary piece
approaching the Gulf Coast, with both of these impulses rotating
eastward during D2, producing the most intense troughing on
Thursday. Within this progressive flow, even as these lead impulses
rotate away on Friday, the next vorticity lobe will follow
immediately in its wake, moving from the Northern Plains to the
Mid-Mississippi Valley on D3.

This pattern will produce multiple days of lake effect snow (LES)
downwind of the Great Lakes, especially in the more northerly belts
as winds become NNW beneath strong CAA. 3-day WPC probabilities for
LES are high (>70%) for more than 8 inches in the higher elevations
of the U.P. including the Huron and Porcupine Mountains, as well as
along the E/SE shore of Lake Michigan into northern Indiana, and
across the Tug Hill Plateau, with lower but still significant
probabilities (30-50%) for 8+ inches along the Chautauqua Ridge.
The heaviest LES is likely in a single band off Lake Michigan into
SW MI/NW IN late Wednesday through late Thursday.

Across the Central Appalachians and Northeast, the lead shortwave
will not only work together with an Atlantic-offshore jet streak to
create low pressure development across the Northeast, but also drag
an arctic front from the Ohio Valley through the Mid-Atlantic on
Thursday. This will create a short period of heavy upslope snow
from the higher elevations of NC through the Laurel Highlands of PA
where WPC probabilities are moderate (50-70%) for at least 4
inches, generally above 3000 ft, with locally 6-8 inches possible.
Farther north into Upstate NY and northern New England, a weak
TROWAL may pivot westward north of the surface low and combine with
an inverted surface trough to enhance snowfall D2. Trends in the
guidance continue to shift the heaviest snowfall north into Canada,
but a narrow corridor of heavy snow is likely, reflected by WPC
probabilities for 6+ inches that are 50-70% from eastern Lake
Ontario (where some lake enhancement is likely) through the St.
Lawrence Valley and the Adirondacks.

Finally, on D3 with the next shortwave digging out of Saskatchewan
into the Upper Midwest, height falls and modest warm/moist
advection will create a swath of generally light snow, followed by
strong winds behind yet another arctic front. WPC probabilities
indicate only a 10-30% chance for at least 4 inches of snow for
parts of SD/MN/WI, but WSSI-P suggests an increasing threat for
blowing snow impacts just behind this wave, so travelers should be
prepared for hazardous driving Friday despite the modest snowfall
amounts forecast.


Weiss


$$

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