FOUS11 KWBC 060829
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
329 AM EST Fri Feb 6 2026

Valid 12Z Fri Feb 06 2026 - 12Z Mon Feb 09 2026

...Great Lakes, Central Appalachians, Northeast, Mid-Atlantic... Days 1-2...

Guidance continues to indicate a period of extreme cold will plague
the Northeast, Central Appalachians, and Mid-Atlantic states this
weekend before finally relaxing next week. For this extreme cold,
Key Messages have been issued which are linked below (Key Messages 1).

The driver of this cold will be a sharpening shortwave trough
digging across the Great Lakes today and then amplifying as it
pushes off the Mid-Atlantic coast Saturday. This should become a
closed low south of New England, with the overlap of LFQ diffluence
in a strengthening downstream jet streak with the strong height
falls at 500mb leading to a rapidly deepening surface low well
offshore. While this surface low itself will be too displaced from
the coast to bring notable weather impacts, its pressure gradient
will help enhance northerly winds across the region, driving an
arctic cold front southward, while an inverted trough pivots near
eastern New England Saturday before moving offshore. This will
result in three areas of potential heavy snowfall through Saturday.

1) Central Appalachians: the shortwave itself will cross the
Central Appalachians Friday morning into the afternoon, pushing the
strong front southeast beneath it. While some synoptic ascent into
a modestly moistening column will result in widespread light snow,
the heaviest accumulations are likely to occur within post-frontal
upslope ascent. This lift should maximize into the lower portions
of the deepening DGZ, and as moisture from the Great Lakes gets
advected southward, this will result in periods of heavy snowfall
for which the WPC prototype snowband tool suggests will exceed
1"/hr at times. The heaviest snowfall is expected Friday evening
through early Saturday morning before the column dries, and WPC
probabilities indicate a high risk (>70% chance) of at least 6
inches of snow across the higher terrain of WV, with locally 10+
inches possible, and at least 4 inches (50-70% chance) extending
from the Laurel Highlands down into the higher terrain of NC/TN.

2) Great Lakes: Although ice cover across the Lakes has increased
dramatically the past few weeks, the intense CAA behind this front
will still support some lake effect snow (LES) across the open
waters, especially south of Lake Ontario and Lake Superior D1. The
intensity of this snowfall should be somewhat muted, but WPC
probabilities for 4+ inches reach as high as 70-90% south of Lake
Ontario, with slightly lower probabilities across the eastern U.P.
and northwest L.P. of MI.

3) Eastern New England: The most challenging aspect of this
forecast is what happens across eastern New England, especially
along the coast from near Portland, ME, through Boston, MA, and
onto Cape Cod. Strong N/NE winds within the CAA should produce
ocean enhanced snowfall (OES) especially for Cape Ann and Cape Cod,
with some enhancement possible anywhere along the coast from Boston
southward. At the same time, the guidance, while very different in
its spatial positioning, all show some degree of an inverted trough
pivoting across the region, with low-level convergence aiding in
ascent. While there is uncertainty in the placement, and this
should come into better focus as we get more steadily into the
high-res windows, there is nearly uniform agreement of this
occurring, and with some fgen efficiently intersecting the lowering DGZ,
this will likely result in periods of heavy snowfall. Despite the
uncertainty, WPC probabilities have crept upwards to above 50% for
4+ inches from near Portsmouth, NH south to Boston and Plymouth,
MA,but some locally higher amounts are probable as reflected by a
lot of spread in the WSE plumes for coastal areas.

Finally, although not expected to be widespread, scattered snow
squalls are possible along the arctic front as it digs southward
Friday night into Saturday from New York state down through central
WV and into New England. Any convective snow showers or squalls
that develop will contain brief heavy snow rates and strong winds,
leading to hazardous travel.

...Pacific Northwest and Northern Rockies... Day 3...

A shortwave emerging from the Northern Pacific will track eastward,
moving onshore WA/OR Sunday night and then deamplifying as it
approaches the Northern Rockies by the end of the forecast period.
Downstream of this impulse, a period of enhanced moisture advection
will occur, both in response to modest WAA as well as a weak upper
jet streak pivoting into Canada. Together, this will drive IVT
onshore in a corridor from OR through the Northern Rockies, which
has a high probabilities (>80%) of exceeding 250 kg/m/s. The
duration of this IVT is likely to be limited, and the corresponding
WAA will surge snow levels up to 5000-6000 ft before falling the
latter half of D3 (due to CAA behind an accompanying cold front)
back down to 2000-3000 ft. However, most of the precipitation
should occur within the warm plume, and this is reflected by WPC
probabilities indicating a high risk (>70% chance) for at least 4
inches of snow for the higher terrain of the Cascades and into
parts of the Northern Rockies near Glacier NP, and into the
Sawtooth/Salmon River ranges.

Weiss

...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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