527
FXUS66 KSTO 292145
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
245 PM PDT Thu Oct 29 2026



.KEY MESSAGES...

 - Mostly dry weather conditions through today

 - Chances of light rain and mountain snow returns late this
   evening through Friday for the Sierra

 - A storm system will bring cooler temperatures, rain and
   mountain snow above 6000-7000 feet Saturday into Sunday

 - Winter Weather Advisory in effect from 8 AM Saturday to 7 AM
   Sunday for elevations above 7000 feet in the Sierra Nevada

 - High pressure will promote a drying and modest warming for
   Sunday and Monday

 - Breezy north to east winds Sunday into Monday


&&

.DISCUSSION...
A larger upper-level trough centered over the Northeastern Pacific
will continue to deepen offshore today and Friday, with embedded
shortwave trough approaching the area this afternoon. High level
clouds have been promoting sky obscuration across the area, but
mostly dry weather conditions is expected to persist through
today. The aforementioned shortwave trough will bring chances of
of showers and mountain snow above 7500 feet over portions of the
Sierra later this evening through Friday, and tapering off Friday
evening. There is a low chance for elevated isolated
thunderstorms on Friday. Elsewhere, will see mostly dry weather
with mid to high clouds streaming across the area.

The aforementioned upper level trough is expected to weaken and
moves across the region Saturday through Sunday. A system will
moves across the area Saturday into Sunday bringing an increasing
chance of rain and mountain snow above 6000-7000 feet. Precipitations
amounts has been trending higher with this system, especially
over the Sierra. Most likely rain total amounts range 0.5 to 1.5
inch over the mountains and 0.25 to 0.75 for the Sierra foothills.
Meanwhile, lighter amounts ranging from a trace to a tenth of an
inch are expected for the Valleys and Coast Range.

Colder air aloft will bring an increasing instability on Saturday,
capable of produce brief heavy downpours and a chance of isolated
thunderstorms. Snow levels are expected to be above 7000 feet on
Saturday, lowering to 6000-7000 feet Saturday night into Sunday.
The snowfall total amounts are also trending higher with this
system over portions of the Sierra Nevada, with the heaviest
snowfall amounts expected above 7000 feet. NBM probabilities
indicates there is a 50% chances of 3 inches or more of snow for
the Donner Pass, and a 25% chances for snowfall exceeding 6
inches. Total snow accumulations up to 8 inches, with up to 12
inches at the highest peaks. Minor accumulations of up to 2 inches
possible down to 6000 feet. A Winter Weather Advisory is now in
effect from 8 AM Saturday to 7 AM Sunday for Northern Sierra
above 7000 feet, including Highway 50 and Interstate 80.

Ensemble cluster shows a ridge building in right after the trough
exits on Sunday. Resulting in drying and modest warming Sunday
through early next week. Breezy to east northerly winds are
expected to developed across the area, with the strongest winds
over the Sierra.

&&

.AVIATION...

VFR conditions prevail across interior NorCal next 24 hours.
Surface wind gusts generally below 12 knots across Valley TAF
sites next 24 hours. Mountain surface wind gusts up to 20 kts.
Low to mid-level clouds will move into the Valley around 08z
Friday, slightly lowering ceilings at TAF sites.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 8 AM Saturday to 7 AM PDT Sunday
for Sierra (Cal-Tuo) Above 5000 ft-Sierra (El Dorado-Amador)
Above 5000 ft-Sierra (Sierra-Placer) Above 5000 ft.

&&

$$