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FOUS11 KWBC 032058
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
358 PM EST Sat Jan 3 2026

Valid 00Z Sun Jan 04 2026 - 00Z Wed Jan 07 2026


...Northern Plains/Upper Midwest/Great Lakes/Interior Northeast...
Days 1-3...

Single band lake effect snow from Lake Ontario is forecast to sag
south as it eases in intensity into the evening the latest clipper
(this one perhaps the weakest this week) works its way east from
Michigan.

The next clipper of Pacific origin and crosses the northern Plains
early Sunday with widespread wintry precip breaking out around
midday near the MN/Dakotas border. Elevated moisture (PWs above
0.5" and the 90th climatological percentile), ascent driven by
height falls/PVA, intensifying left-exit jet level diffluence, and
strengthening WAA will accompany this feature. Rates quickly become
heavy over northern MN Sunday afternoon with a wintry mix on the
southern edge of the precip, but mostly snow, heavy at times with
>1"/hr rates (per the 12Z HREF) within banded structures. The
system will remain progressive, with a preference for QPF from the
wetter global models vs the CAMs which have a narrower precip
shield as often has on synoptically forced winter storms. The risk
for 6" through Sunday night has risen over northern MI with Day 1.5
PWPF now around 35% around both sides of the Straits of Mackinac.
Day 1.5 probs for >4" are over 30% from the Bayfield Peninsula of
WI across the U.P. and Upper L.P. along with far northern WI and
northern Door Co.

The strong warm nose could result in a corridor of impactful icing
over central MN (including the Twin Cities metro) and
western/central WI. WPC ice probabilities for >0.1" remain less
than 10%, but some icy roadways and hazardous travel are possible
Sunday afternoon and evening.

This wave tracks into New York Monday before weakening as it
continues to push into a ridge. Day 2 PWPF for >4" is limited to
around 30% for the Tug Hill Plateau where some lake enhancement can
be expected on westerly low level flow.

The next wave is southern stream, coming from CA and crossing
Nebraska/Iowa Monday night. The northern precip shield should bring
mainly light to moderate wintry mix over central MN and northern
WI into Tuesday. While 12Z guidance generally agrees on a narrow
swath of mainly freezing rain, there is still meridional
differences of central vs northern WI. Even the 12Z EC-AIFS shifted
north with its QPF axis (northern WI) from the 06Z run (which
favored north-central WI). So stay tuned on Tuesday icing threats
for the Upper Midwest.



...Western U.S. Mountain Ranges...
Days 1-3...

A persistent longwave trough positioned off the Pacific Coast will
continued to shed impulses onshore at least through Monday night,
with each subsequent impulse spreading energy across most of the
Intermountain West.

The southern stream trough off CA with the northern stream end
shifting over the Northwest will maintain 850-500mb heights at or
below the 10th climatological percentile into Monday before finally
relaxing as the southern stream low likely closes off west of CA.
Pacific moisture flows inland on WAA ahead of the main trough axis,
but lowering height falls will allow lower snow levels to continue
shifting across the West.

Sierra Nevada...Days 1/2...

The current trough pushing into OR/northern CA this afternoon
shifts south across CA through Sunday with the heaviest precip on
the Sierra Nevada. Snow levels drop to around 6000ft tonight on
along the length of the Sierra Nevada and even drop to around
6500ft in the SoCal ranges Sunday.

The next wave is the northern stream that shifts into the OR/WA
coast Sunday and works its way down through central CA into Monday
night before focusing offshore. Snow levels on the Sierra Nevada
are lower with the next wave, generally around 5000ft, but drop to
around 4500ft Monday evening though snow rates will be less than
from the current wave.

Day 1 PWPF for >24" is 50-80% above 7000ft across the length of the
Sierra Nevada. Then for Day 2 the PWPF for additional >12" over
the length of the Sierra Nevada is 50-80% above about 6500ft.

With prolonged heavy snow for the Sierra and northern CA
mountains, totaling 4-6+ feet in some areas, and snow levels
below pass levels, travel will remain extremely challenging through
Monday. Localized extreme impacts are possible due to the
combination of heavy snow and low SLR.

Cascades...Days 1-3...
Repeating waves into the Pacific Northwest through Sunday evening
maintain moderate to heavy snow rates on the WA/OR Cascades with
snow levels remaining around 4000/5000ft tonight. As the northern
stream shortwave trough pushes through later Sunday, the snow
levels drop to 3000/4000ft before rates ease Sunday night. Day 1
PWPF for >8" is 50-80% in the higher Cascades with 40-70% for >6"
on Day 2.
There's a lull for the Cascades then through Monday night before
the next northern stream trough approaches Washington with snow
levels starting on the WA Cascades around 1200ft Tuesday morning,
rising to around 2500ft by Tuesday evening. Day 3 probs for >6" are
50-90% throughout the WA Cascades and Olympics above about 2500ft.


Northern to Central Rockies...
Days 1-3...

The current lull over the northern Rockies ends by this evening as
moisture streaming from CA flows across ID and western MT/WY
through tonight before drifting south to UT/southern WY Sunday
night. Snow levels begin around 6000ft at onset and drop to around
5000ft Sunday (3000-4000ft for northern ID/MT). Day 1 snow probs
for >8" are 50-80% in the central ID and western WY ranges as well
as around Glacier NP and west through northern ID. The focus shifts
south a bit for Day 2 where probs for >8" are 50-80% for the
Wasatch Front and Uinta as well as the Wind River again in WY while
central ID values are around 50%.

Day 3 probabilities are lower across the Rockies as rates decrease
under weakening flow. Probs for >6" are 50-80% in the Tetons and
40-60% in the Park Range of CO, the Wind Rivers, central ID up
through the Bitterroots.


Jackson


$$

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