Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
157 PM EDT Mon Oct 14 2024

Valid 00Z Tue Oct 15 2024 - 00Z Fri Oct 18 2024

...Northeast...
Days 1-2...

A leading upper low tracks north over Maine this evening before
stalling over the mouth of the St Lawrence into Wednesday. The next
wave is positively tilted trough over the Boundary Waters of MN
this afternoon which will swing south into the Midwest tonight and
over the southern Appalachians Tuesday night. Steep lapse rates
should trigger some potent snow showers, especially in higher
terrain above 3,000ft. Snow showers look to linger in the northern
Appalachians until Wednesday morning when the trough axis moves
east and off the New England coast.

Additional snow over 4" should be confined to the higher
Adirondacks,
Green, and White mountains.


...Northwest...
Days 2-3...

An upper shortwave trough brings a surge in 850-700mb moisture and
associated height falls will cause snow levels to gradually drop
from around 6000ft Tuesday night to around 4000ft by Wednesday
evening over the WA Cascades. The airmass is not particularly cold
for the time of year, so this setup favors snowfall accumulation
in the Olympics and Cascades down toward the highest mountain
passes Wednesday night until Thursday morning when a reinforcing
trough crosses western WA brining and end to moderate precip rates.

This secondary wave digs down through far northern CA Thursday with
decent precip rates and height falls over the northern
Intermountain West to the northern Rockies. Day 3 WWD probs for
more than 4" are 50-80% for higher terrain of the WA/OR Cascades
and the Salmon River mountains in ID and the northern Absarokas in
MT.


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


Jackson