Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
305 AM EST Mon Nov 17 2025

Valid 12Z Mon Nov 17 2025 - 12Z Thu Nov 20 2025

...Northeast/Great Lakes...
Day 1...

A deep closed low now centered over the Canadian Maritimes will
begin to lift north this morning and then accelerate later in the
day. Supported by deep northwesterly to west-northwesterly winds in
its wake, ongoing orographic and lake effect snow showers will
continue but gradually wane through the day. The northern
Adirondacks, Green, and White mountains will remain the focus for
upslope snows, with some potential for several more inches in some
spots, especially along the northern Greens, where WPC
probabilities for additional accumulations exceeding 4 inches
remain high.

Further to the west, there is a decent signal for a single band
intensifying off of Lake Ontario and shifting east across the
Finger Lakes, with WPC probabilities indicating several inches are
possible east-southeast of Syracuse.

Lastly, the band off of Lake Erie with a connection extending back
to Lake Superior is expected to wane and shift east, most likely
producing just another inch or two across parts of southwestern New
York and northwestern Pennsylvania today.

...California to the Central and Southern Rockies...
Days 1-2...

An upper low will move across Colorado and Wyoming this morning.
Snow will continue to fall this morning across the western and
south-central Wyoming ranges, as well as the western Colorado
mountains, with additional accumulations remaining light for most
areas. Favorable upper jet-streak forcing along with moist
southwesterly flow may support some higher totals along the Sierra
Madre, Park Range, and Medicine Bow mountains in south-central
Wyoming and north-central Colorado. WPC probabilities indicate
additional totals over 4 inches are likely, especially for areas
above 8,000 ft.

A second low closing off within the base of a sharp trough
approaching northern California will continue to deepen and drop
south along the coast through today into early tomorrow. This
system is expected to linger as it settles along the southern
California coast tomorrow before rotating inland as yet another
Pacific system moves toward California late Wednesday into
Thursday.

Areas of heavy snow are forecast to spread south along the Sierra
Nevada today, before diminishing tonight, but with light amounts
continuing across parts of the central and southern Sierra through
Tuesday. WPC probabilities indicate that two-day totals are likely
to exceed 8 inches for many locations in the central Sierra above
8,000 ft. Some locally heavy totals, exceeding 8 inches, are also
expected farther east in parts of the central and southern Nevada
ranges, and the southwestern Utah mountains.

...Central Plains/Upper Midwest...
Days 1-2...

The previously noted low exiting the Rockies today is forecast to
move steadily east from the Central Plains into the mid and upper
Mississippi Valley tonight. Low to mid level frontogenesis along
with a coupled upper jet will support a stripe of moderate
precipitation developing from eastern South Dakota, through
southern Minnesota, into southern Wisconsin tonight. Dynamic
cooling will support rain changing to snow where this heavier band
sets up. While probabilities for accumulations beyond an inch or
two remain low, the potential for locally heavier amounts cannot be
ruled out.

Pereira