Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
314 PM EDT Mon Oct 13 2025

Valid 00Z Tue Oct 14 2025 - 00Z Fri Oct 17 2025

...California & Central Nevada...
Days 1-2...

...First significant snowfall event of the season impacts the
Sierra Nevada tonight through Tuesday night...

A deepening low pressure system shifting south just off the far
north California coast this afternoon will swing inland across the
central California coast late tonight, cross the Sierra Nevada
Tuesday night, and north-central Nevada on Wednesday. The fairly
deep low will decrease snow levels from around 7000ft over the
Sierra Nevada tonight to as low as 5500ft Tuesday evening under the
upper low. Snow levels drop to around 6000ft over the central NV
for Tuesday night and Wednesday. A strong inland moisture surge
ahead of the low with PW around 1" will allow for moderate to heavy
snow rates above the snow level. 12Z HREF mean snow rates are
1-2"/hr over the central/southern Sierra Nevada from 06Z tonight to
15Z Tuesday.

WPC probabilities show moderate-to-high chances (40-80%) for at
least 24" of snowfall in 24hrs from 06Z tonight to 06Z Wednesday
above about 8000ft. Probabilities through that time for >8" are
30-70% around 7000ft (including Donner Pass on I-80). The WSSI
highlights Major Impacts for the High Sierra and remote central NV
ranges with moderate impacts for most cross Sierra road passes.


...North-Central Rockies...
Day 3...

The low fills as it crosses the Great Basin, but remains closed as
it crosses over WY on Thursday. Lee-side cyclogenesis forms over
southeast WY Wednesday night with an increasing easterly component
to the low level flow to aid moisture transport over the western WY
ranges through Thursday morning with snow levels around 7000ft.
However, the rates are not expected to be that great with mainly
20-30% probs for >8" snow in 24hr from 00Z Thur to 00Z Fri for the
Absarokas and Wind River Range. An exception is over the Tetons
where those probs are 40-60%.


The probability of significant freezing rain across CONUS is less
than 10 percent.


Jackson