Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
253 PM EST Mon Nov 10 2025

Valid 00Z Tue Nov 11 2025 - 00Z Fri Nov 14 2025

...Lake effect snow continues across the Great Lakes, Northeast,
and Appalachians through Tuesday, while the next Atmospheric River
event is expected to bring heavy snow for the Sierra Nevada by
Thursday night...


...Great Lakes through Interior Northeast and Appalachians...
Day 1...

Anomalously deep upper trough over the Eastern U.S. and surface low
racing north from the Gulf of Maine into eastern Canada will remain
the driving force behind a cold and windy weather pattern though
the Day 1 period. This will keep the lake effect snow machine
turning as well as upslope snowfall into the Appalachians.
Additionally, a blossoming area of precipitation near the left-
exit region of a 180kt 250mb jet streak is forecast to briefly
impact parts of northern New England.

Starting with the lake effect and upslope snow into the
Appalachians, 850mb flow remains northwesterly to start the Day 1
period but will shift more westerly during the day on Tuesday as
the upper low lifts out of the region and a WAA regime takes hold
through the remainder of the forecast period. This will allow for
Lake Superior and Lake Michigan snowbands to diminish by Tuesday
morning, with better fetch remaining off Lake Erie/Ontario/Huron
through Tuesday night before low-mid level temperatures begin to
warm back to around -5C. Upslope flow into the central/southern
Appalachians also continues early on Day 1 as the southern lobe of
the upper low crosses into western NC to start the period. This may
allow for even some flurries/snow showers to reach eastern NC on
Tuesday morning. WPC probabilities for >4" on Day 1 are 30-50%
along the TN/NC border in the southern Apps and in central WV
Allegheny Mts. For the Lower Great Lakes, WPC probabilities for
>8" are 50-80% downwind of Lake Erie from northwest PA to far
western NY as well as downwind of Lake Ontario and the Tug Hill.
Northern VT/NH also have moderate (40-70%) probabilities for >4" of
snow and coincide with 12z HREF highlighting the region for 1"/hr
snowfall rates between 00-03Z tonight.


...Sierra Nevada...
Day 3...

The next Atmospheric River event to impact the West Coast this fall
is forecast to begin impacting the Sierra Nevada with heavy snow by
the end of Day 3 (00Z Friday). Some timing uncertainty remains, as
depicted by the WPC ensemble clusters, with the GEFS suite
primarily faster in moving precipitation onshore. Regardless, this
plume of moisture is poised to be potent with 80% probabilities of
>500 km/m/s IVT from the 00z EPS, but progressive and limit extreme
snowfall amounts. Snow levels will start out very high (above
8,000ft) and drop significantly to as low as 5,000ft Thursday night
per the 10th percentile NBM. WPC probabilities for >12" (warning
criteria for the central Sierra) through 00Z Friday are generally
60-80% and above 6,000ft. Additional snowfall is likely after 00Z
Friday.


The probability of significant icing is less than 10 percent.


Snell