Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
243 AM EST Sat Nov 18 2023

Valid 12Z Sat Nov 18 2023 - 12Z Tue Nov 21 2023

...The West...
Days 1-3...

Active period in the West will start to quiet down by early next
week. Lead system (weakening ex-upper low) moving into NorCal
today will spread snow across the Sierra and Great Basin into the
Rockies where precipitable water values will remain elevated at
about +1 to +2 sigma. Stronger height falls via a robust surface
cold front will dive into the Pac NW tonight, helping to drive
snow levels down 2000-3000ft from where they start today. This
will bring snow to some passes over the region as snow levels fall
to around 3500ft as the precipitation winds down from northwest to
southeast late Sunday into Monday. Upslope flow and upper
diffluence will drive modest snow totals in the OR Cascades where
WPC probabilities for at least 8 inches are high (>70%). Light to
modest snows will overspread the Blue Mountains and central Idaho
range as well as the system moves southeastward.

Over the Great Basin to the central Rockies, the combination of
the lead weakening system and stronger subsequent system may bring
multi-day totals over a foot to the Utah ranges including the
western Uintas and Wasatch where WPC probabilities for at least 8
inches are highest (>50%), generally above 8000ft. Over CO,
strongest height falls move in on Sunday into early Monday as the
cold front weakens and then reforms over the High Plains in
response to the mid-level trough closing off. Several inches of
snow are likely over the CO Rockies into the San Juans and Sangre
de Cristos into northern NM.


...Northeast...
Day 2...

A shortwave and surface cold front will swing through the
Northeast on Sunday with generally light snow for the higher
elevations in NY and northern New England. Some favored areas of
the Green/White Mountains and Adirondacks may see up to or just
over 4 inches of snow, though WPC probabilities for more than that
are around 10%.


For Days 1-3, the probability of significant icing (at least
0.25") is less than 10 percent.

Fracasso