Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
403 AM EDT Wed Nov 02 2022

Valid 12Z Wed Nov 02 2022 - 12Z Sat Nov 05 2022

...Western U.S....
Days 1-2...

Digging troughing in the Pac NW today will continue to deepen well
into the Southwest U.S./Four Corners region by Friday then
steadily moving into the Plains. A lead shortwave on the eastern
side of the longer wavelength trough will push through Idaho and
western Montana today, promoting an axis of heavier snow over the
higher terrain. Strong height falls coupled with modest lift
through the DGZ and orographic enhancement will favor the Uintas
in UT today and the San Juan mountains in CO/northern NM tomorrow
as the system moves eastward. In southern CO, totals may exceed a
foot above 8000ft in the San Juans with more modest snow farther
north through the CO Ranges. Some light accumulations are likely
outside the mountains in CO as colder air and some easterly
upslope flow change the rain to snow. WPC probabilities are high
for at least 4 inches in many mountainous areas. To the north, the
Wyoming ranges will likely pick up appreciable accumulations due
to convergence and upslope/terrain enhancements, especially the
Wind River Range and Bighorn Mountains.

Days 2-3...
Back to the Pacific Northwest, the next strong atmospheric river
will approach via a strong North Pacific jet (>150kts) late Day 2
into Day 3. Lower snow levels to start will support some snow to
some lower elevations in easter Washington but will quickly rise
as strong WAA brings in milder air to the region. IVT values may
rise to 1000 kg/m/s (quite a strong Atmospheric River) but will
also take snow levels up to 7000-8000ft. Farther east, snow levels
will be a bit lower over northern/central ID into western MT where
modest snowfall is likely. WPC probabilities for at least 4 inches
of snow are moderate (>40%) above about 4000ft.

The probability of significant icing greater than 0.25" is less
than 10 percent.

Fracasso/Taylor