FOUS11 KWBC 082018
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
318 PM EST Fri Nov 8 2024

Valid 00Z Sat Nov 09 2024 - 00Z Tue Nov 12 2024


...Colorado Rockies and Adjacent High Plains...=20
Day 1...

...Heavy snow and major impacts continue for portions of the=20
Colorado Rockies and Interstate 25 corridor into Saturday=20
morning...

Strong low pressure system causing this major winter storm will
track north along the CO/KS border tonight, producing final rounds
of heavy snow east from the Front Range over eastern CO into the
overnight before diminishing into Saturday morning.=20
Downstream height falls and divergence will combine with a=20
modestly coupled jet structure to produce impressive large-scale=20
ascent across the Southern/Central Rockies and High Plains as well=20
as a surface low center tracking north over western KS tonight.=20
This low is accompanied by enhanced forcing through persistent=20
moist isentropic lift which will continue to bring TROWAL through=20
eastern CO into the overnight. An axis of elevated instability=20
beneath the TROWAL, collocated with an axis of deformation, will
continue to allow 1-2"/hr snowfall rates in the heaviest TROWAL
bands. This activity will lift from southeast CO through at least
the Palmer Divide through this evening with bands weakening a bit
as they track north from the Denver metro to southern WY.=20

WPC snow probs are mainly terrain based with 30-70% values for >6"
additional after 00Z across the greater Palmer Divide, the Front
Range, and right around the Raton Mesa. Near 10% probs are along
the Cheyenne Ridge in southeast WY. However, the intensity of the
banding should allow heavy snow to overcome more marginal thermals
and accumulate in the valleys, so areas around CO Springs and at
least portions of the Denver metro should see some additional=20
impactful snow tonight.=20

As the low occludes and shifts over Neb on Saturday, the moisture=20
moisture fetch is shunted east and thermals farther east do not=20
support snow, so the heavy snow threat generally ends with the
Cheyenne Ridge. The Black Hills mainly stay below the snow level,
so impactful snow is not expected there, but some flakes should be
seen on Saturday.


...Northwest...
Day 3...

A potent upper trough ejecting from a deep Gulf of Alaska low=20
approaches the Pacific Northwest coast Sunday night and digs down
to the northern Great Basin on Monday. Snow levels in the moisture
surge ahead of the trough rise to around 6000ft in western WA and
7000ft in OR/northern CA before dropping to 4000-5000ft under the
trough on Monday. Day 3 PWPF for >6" are 30-70% over the length of
the Cascades. More impactful snow is likely Monday night into
Tuesday with at least the higher passes in WA seeing accumulating
snow then.


The probability of significant ice across the CONUS is less than=20
10 percent.


Jackson


...Winter Storm Key Messages are in effect...=20

Southern/Central Rockies and High Plains:
https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late=
stKeyMessage_1.png__;!!DZ3fjg!9_n9QFVgwaIkhJLdPvVZONqU-53YTaKPIqRb9VEkyRZ5C=
hnyEwRZMz3sCk5oLm8fYzvDlr_oZxTuwF5K0RccR2_mGlY$=20

$$

=3D =3D =3D
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