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FOUS11 KWBC 080813
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
313 AM EST Thu Jan 8 2026

Valid 12Z Thu Jan 08 2026 - 12Z Sun Jan 11 2026


...Pacific Northwest, Great Basin, Northern Rockies...
Days 1-1.5...

A shortwave trough over northern CA this morning will strengthen as
it tracks south and east into the southwestern U.S.. Farther north,
a second shortwave trough over British Columbia will also dig
farther south across the northern Rockies and northeast High
Plains. Residual 700-300mb Pacific moisture will stream across the
Pacific NW and into the both the Northern Rockies and Great Basin
to continue to produce additional mountain snow through Thursday.
Snow levels in the northern Cascades and Olympics will be as low as
1,000ft today, but the heavier snowfall will remain confined to
elevations above 2,000ft. Farther east, the northern Rockies'
heaviest snowfall will be above 5,000ft and above 6,000ft in the
Great Basin. WPC probabilities show high chances (>70%) for
snowfall totals >6" for elevations above 3,000ft in the Cascades
and Olympics. Similar high chance probabilities are present in
parts of the Lewis, Bitterroots, Blue, and Teton Ranges for
additional snowfall >4". Snow will linger longest over the Cascades
and northern Bitterroots through Thursday night, but as the long
awaited upper level ridge builds in on Friday, snow levels will
rise and snow will taper off across all mountains ranges into the
start of the weekend.


...Four Corners into the High Plains...
Days 1-2...

A pair of shortwave troughs will be responsible for rounds of
moderate-to-heavy snowfall over the Central and Southern Rockies,
with some snowfall into the central High Plains also expected. This
morning, a strengthening storm system over western KS and eastern
CO brought along a plume of subtropical moisture that is streaming
over the Four Corner states. Snow levels will dip to as low as
5,000ft in central CO and central UT with light snow falling in the
SLC and Denver metro areas. As this disturbance races into the
Midwest this afternoon, a second and more vigorous upper level
shortwave over the Great Basin heads east for the Four Corners
region, bringing with it not only additional Pacific moisture but
height falls, better PVA, and jet streak dynamics aloft. Guidance
shows a healthy area of 700mb Q-vector convergence shifting from
the Mogollon Rim and Wasatch this morning to the central and
southern Rockies by this afternoon, where periods of snow will
envelope most mountain ranges. Snow levels along the Mogollon Rim
will be as low as 6,000ft, while central and southern UT sees snow
levels still hovering as low as 5,000ft. The Gila Mountains and
southwest CO will also see an uptick in snowfall this afternoon
before tapering off early Friday morning.

Farther east, as the enhanced Q-vector convergence heads for the
Front Range of the Rockies and the High Plains this evening, a
closed 700mb low will develop over northern NM that gives rise to a
surface low forming in lee of the Sangre De Cristo mountains. Low-
level easterly winds over the central High Plains fosters upslope
flow into southern CO and northern NM beginning Thursday night and
peaking Friday morning as the 700mb low tracks just south of Raton
Pass. There remains some disagreement on the placement of the best
700mb FGEN as the 700mb low emerges into northeast NM and tracks
towards the OK/TX Panhandles. Where the best FGEN forcing sets up
and the strength of the 700mb low will be vital in where the
heaviest snowfall occurs and how far east away from the Raton Mesa
and Front Range the band of heavy snow can advance. Beneath the
700mb FGEN, >1"/hr snowfall rates are expected. As the 700mb low
moves northeast Friday afternoon, it will weaken and open up into a
progressive 500mb shortwave, resulting in frontolysis over western
KS that reduces precipitation rates and weakens dynamic cooling
aloft.

At this time, WPC probabilities are highlighting the usual
suspects (Palmer Divide, Front Range, Raton Mesa) as having
moderate-to-high chances (>70%) for snowfall totals >4". I-25 at
Raton Pass sports moderate-to-high chances (50-70%) for snowfall
totals >6". Localized snowfall totals >8" along the peaks of the
Sangre De Cristo and Raton Mesa are possible. Farther east, WPC
probabilities show moderate chances (40-60%) for snowfall totals
>4" in southeast CO , southwest KS, the far western OK Panhandle,
and the northwest tip of the TX Panhandle. The WSSI shows
widespread Minor Impacts (winter driving conditions; use caution
when driving) for much of the central High Plains with localized
Moderate Impacts possible.


...Upper Midwest & Great Lakes...
Days 1-3...

An active stretch of potent storm systems will bring a wide range
of winter precip types to the Midwest and Great Lakes the
remainder of the week. The first storm system will track from KS on
north and east into IA this evening, then over northern MI by
Friday morning. Dynamic cooling beneath a coupling jet-streaks
structure is a plausible scenario from as far south and west as
eastern NE to as far north as the MI U.P.. Given the rapid
progression of the QPF shield, accumulating snow over 1" will be
tough for areas south and west of northern WI. However, over
northern WI and the MI U.P., the timing of the changeover to snow
coincides with the middle of the night, allowing for a better
chance for snowfall accumulations. Marquette's area in particular
will have better chances for accumulating snow as onshore, lake-
enhanced snowfall ensues. Snow tapers off Friday morning as the
storm races north into Ontario. WPC probabilities shows moderate
chances (>50%) for snowfall totals >4" in MI's Huron Mountains with
similar >50% probabilities for >2" extending southward into
northern WI. There is also the potential for light ice
accumulations from northern IA and southern MN to northern WI and
the western MI U.P. with WPC probabilities showing moderate chances
(40-60%) for ice accumulations over one-hundreth of an inch. Ice
accumulation could occur near the evening rush hour in southern MN
and central WI.

By Saturday night, the shortwave trough responsible for the heavy
snow in the the southern and central Rockies/High Plains heads east
towards the MS Valley at the same time as a closed 500mb low over
in Canada plunges south into the Upper Midwest. Guidance has come
into better consensus on the northern stream feature effectively
shearing the southern disturbance and becoming the more dominant
feature. As the 500mb low will direct PVA at the Great Lakes, a
strengthening wave of low pressure and 850-700mb WAA will produce a
larger shield of snow developing initially over southern WI and
northern IL. As moisture wraps northward around the deepening
850mb low over northern MI, a TROWAL will pivot over northern WI
and the MI U.P., prompting the development of heavy snow in these
areas Saturday afternoon and persisting into Saturday night. The
low will occlude over Lake Huron early Sunday morning as the
deformation zone of heavy snow pivots over the tip of MI's Mitten.
Once occluded, the upper low will weaken and move east as more
progressive flow over the Canadian Prairies kicks the storm east
into Ontario Sunday afternoon.

WPC probabilities show moderate-to-high chances (50-0%) for
snowfall totals >4" from the Green Bay area in eastern WI on north
and east through the eastern MI U.P. and the northern tier of MI's
L.P. (Lower Peninsula). The tip of MI's L.P. are favored to contend
with the heaviest snowfall given their longer duration beneath the
TROWAL and some lingering lake-enhanced snowfall in wake of the
storm early Sunday. WPC probabilities depict low-to-moderate
chances (30-50%) for snowfall totals >8" here with localized totals
approaching a foot a possibility.


...Interior Northeast...
Day 3...

The storm responsible for heavy snow over the northern Great Lakes
on Saturday will also generate a hazardous wintry mix from
northern PA on northward into the northern Appalachians. The
Northeast will lay ahead of a strong >750kg/m/s IVT that will
direct copious amounts of moisture northward on Saturday. At the
same time, a cold front will provide just enough cold/dry air at
the surface with Canadian high pressure to the north creating a
weak CAD signature over the Northeast. This healthy 850-700mb WAA
will support a classic overrunning setup of >0C air aloft causing a
mixture of sleet/freezing rain to unfold beginning Saturday
afternoon and continuing into Saturday night. Precipitation may
start out as snow in far northern New England, where wet-bulb
temperatures down the surface may initially support snow. Still,
the concern is for mountains such as the Catskills, Berkshires,
Greens, Adirondacks, and Whites where surface temperatures have
better odds of staying sub-freezing Saturday night and into Sunday
morning.

While minor ice accumulations over one-hundreth of an inch are
likely (>70% probabilities) in the Adirondack and Green Mountains,
these ranges also could witness ice accumulations over one-tenth of
an inch, resulting in greater odds for hazardous travels
conditions Saturday evening that linger into Sunday morning. In
terms of snow, the latest forecast generally calls for minor
accumulations (2-4" of snow) over northern Maine, but localized
totals over 6" are possible. WPC's WSSI-P shows >50% chances for
Minor Impacts over the Adirondacks, the Green and White Mountains,
and through much of northern Maine late Saturday into early Sunday.


Mullinax





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