Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
329 PM EST Fri Feb 21 2025

Valid 00Z Sat Feb 22 2025 - 00Z Tue Feb 25 2025


...South-Central Texas...
Day 1...

Low level NEly flow from high pressure centered over Arkansas will
persist over the eastern half of Texas through Saturday morning.
Dry/cold air advection in this flow will continue to be overrun by
southerly/Gulf-moisture laden air with an expansion of precip from
South to Central Texas tonight. There is question to how far sub-
freezing temps make it tonight, but as of now there is sufficient
confidence in freezing rain accumulating over central Texas, around
and a bit east of the San Antonio metro area (where WFO EWX has an
advisory). There is potential for some elevated ice glaze farther
south into the CRP CWA, but that fine line is not that clear as of
this time. Day 1 ice probabilities for >0.01" are 40-60% in and
east of San Antonio with 10% probs extending from the Austin metro
to Laredo.


...Pacific Northwest through Northern Rockies...
Days 1-3...

Pacific moisture advects over the PacNW to the northern Rockies
through Monday with a few upper trough passages expected. Higher
elevation snow is expected through the next three days with the
heaviest precip Saturday afternoon through Sunday when there are
rather high snow levels.

An upper low moves over the Queen Charlotte Sound through this
evening. 0.75" PW air flows across WA through Saturday morning with
snow levels west of the Cascades crest generally rising from 4500ft
to 5500ft while persisting around 3000ft east of the crest over the
northern Columbia Basin due to entrenched cold air. Day 1 snow
probs for >6" are 40-70% in the north WA Cascades and the Selkirks
in far north Idaho.

The next wave in this zonal flow arrives to Vancouver Island
Saturday midday with a plume of 1 to 1.25" PW air streaming over
WA/OR Saturday afternoon through Sunday. Snow levels rapidly rise
to 8000ft in this plume for Saturday night, though snow levels drop
to around 6000ft in the north WA Cascades Sunday afternoon under
the next shortwave trough axis. This moisture also spreads across
the northern Rockies where snow levels will be 5000-6000ft. Day 2
snow probs for >6" are 40-70% in the north WA Cascades, western
Sawtooths, Bitterroots, and ranges around Glacier NP. THe pattern
for the Day 3 snow probs for >6" are similar to Day 2 just with
lower probs for the Sawtooths and Bitterroots with an expansion
over the southern Absarokas and Tetons (40-70% there). Three day
snow totals over 3ft are possible in the highest WA Cascades with
more like 1-2ft in the higher Sawtooths, Tetons, and Lewis Range at
Glacier NP.

This is nearly all above mountain road passes and is generally a
beneficial precip event for watersheds in the NW.


Jackson