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FOUS11 KWBC 071950
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
250 PM EST Wed Jan 7 2026

Valid 00Z Thu Jan 08 2026 - 00Z Sun Jan 11 2026


...Pacific Northwest, Great Basin, Northern/Central Rockies...
Days 1-2...

An offshore, well-defined, mid-level shortwave, in tandem with a
~100 kt upper level jet, will dig inland into the Pacific Northwest
this evening. As the northern stream portion of this amplifying
trough advances steadily eastward across the Intermountain West
into the Rockies, a southern stream wave is forecast to dig south
through the Great Basin into the Southwest tomorrow.

Heavy snow currently developing along the Cascades will continue
to spread south through this evening and persist along the range
into tomorrow. Pockets of moderate to heavy snow are also expected
to develop further east from the Blue Mountains into the northern
Rockies tonight. Rates should generally start to wane across the
entire region by late tomorrow as a building upstream ridge begins
to move inland. Areas of light to moderate snow will likely
continue into early Friday before drying out completely across most
areas by late in the day.

The heaviest amounts are expected to fall along the northern
Cascades, where snow levels are forecast to start the period below
2000 ft before dropping below 1000 ft tomorrow. WPC probabilities
indicate that accumulations greater than 8 inches are likely for
many parts of the Washington and northern Oregon Cascades above
2000 ft, including the major passes in northern Washington.

Further south, the digging southern wave will bring crashing snow
levels along with brief but potentially intense snow showers across
the Great Basin tonight. WPC PWPF indicates some of the northern
and central Nevada mountains may see amounts over 8 inches.


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

A lead negatively-tilted shortwave will lift out of the southern
Four Corners tonight into Thursday, briefly interacting somewhat
with the wave digging southward from the Pacific Northwest. This
interaction will allow snow to first blossom across the high
valleys and mountains of the central and southern Rockies. As the
lead wave exits, the elongated vorticity lobe spinning southeast
from the Pacific Northwest will amplify into a deep longwave trough
as it approaches the Four Corners Thursday night. The resultant
jet streak downstream of this trough axis will deepen and pivot
northeast, reaching as high as 140 kts across the Southern Plains,
leaving favorable LFQ diffluence into the High Plains and Four
Corners. Where this jet streak overlaps with the most robust height
falls, lee cyclogenesis will likely result, likely in the
northeast plains of New Mexico as reflected by the latest guidance.

This low will move slowly Friday morning before elongating into
faster flow to the northeast by the end of the forecast period.
Before this occurs, a cold front will dig southward through the
High Plains, with the resulting wind field becoming more E/NE and
upsloping into the terrain of CO and NM. This will provide
additional ascent to the region, which will already be influenced
by favorable synoptic lift, suggesting a period of moderate to
heavy precipitation Thursday night through Friday afternoon. Most
of this will fall as snow, especially as the cold front sags south
and cools the column through favorable CAA. However, there is still
uncertainty into how much snow will fall, especially north of the
Palmer Divide, where a significant low-level moisture gradient is
expected to set up. The ECMWF and its ensemble members have been
much drier and farther north than the other camps in previous
cycles, but the latest guidance trends seem to be coming around on
that idea. Farther south, locations across southern CO and northern
NM have higher confidence in impactful snowfall, including the
higher elevations of the Palmer Divide and along the I-25 urban
corridor. In a normal winter, this event would be fairly run-of-
the-mill, but given how warm and dry it's been so far, this could
still end up being an impactful event for much of the region.

Moderate snow then quickly pulls northeast into KS/OK/TX by Friday
morning beneath the upper jet streak before ending by Friday
evening.

The latest WPC probabilities are high on Day 1 for at least 6
inches of snow across the UT/CO Rockies and into the high
elevations of the southern Rockies, including the White Mountains
of AZ. Late Day 1 into Day 2 as the surface low consolidates and
upslope flow ramps up, WPC probabilities show a moderate to high
risk (50-80% chance), for at least 6 inches of snow in the Front
Range, Palmer Divide, Raton Mesa, and Sangre de Cristos. Low to
moderate probabilities for >4 inches then extend into the High
Plains of southeast CO, southwest KS, far western OK, and far
northwest portions of the TX Panhandle.


...Upper Midwest into the Great Lakes...
Day 3...

The deep positively tilted wave responsible for the snow across
the Four Corners (particularly southeast CO and northeast NM) will
eject northeastward into the central Plains late Friday into
Saturday. Meanwhile, another potent wave dropping southward out of
Canada is expected to rapidly close off over the northern Plains
and Upper Midwest. These two features are progged to phase together
later Saturday into Saturday night, forming a large, closed, mid-
level low over the region. This mid-level evolution, combined with
impressive jet dynamics from a powerful 250mb 150kt+ jet streak,
will support the rapid development and deepening of a surface
cyclone across the eastern Great Lakes. As the low develops, a
stream of rich Gulf moisture (with anomalies in excess of 250% of
normal) will be drawn northward and wrapped into the low pressure
system, likely forming a TROWAL and deformation axis across the
Upper Midwest and Great Lakes. The resulting isentropic ascent and
strengthening frontogenesis underneath this axis could support a
band (or bands) of heavy snowfall, with the potential for
significant accumulations. This is especially the case late Day 3
on Saturday and especially heading into the Day 4 period on Sunday.

The latest WPC probabilities show low to medium chances (20-50%)
for 24-hr snowfall >4" across eastern Wisconsin into northern
Michigan on Day 3, increasing to medium to high (50-80%) just
beyond the forecast period on Day 4. In fact, Day 4 probabilities
increase to over 50% for snowfall >6" across northern Michigan,
highlighting the potential for a more significant event. Given
these already notable probabilities, trends and future model
cycles will need to be monitored closely as we get closer.


Pereira/Miller/Weiss


$$

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