017
FXUS66 KSTO 091949
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
1249 PM PDT Fri Oct 9 2026
For additional details on weather and expected impacts over the
next 7 days, please visit weather.gov/sto/briefing.
.KEY MESSAGES...
- Wind Advisory for the Delta and vicinity Valley locations in
effect 11 PM tonight until 7 AM Saturday.
- Pattern chance this weekend-early next week: cooler
temperatures, chances for precipitation, isolated
thunderstorms, and mountain snow.
- Elevated Fire Weather conditions in the northern Sacramento
Valley today, then again Sunday-Monday including the adjacent
foothills
- Potential for first measurable snow of the season in the
Sierra Sunday PM - Monday, south of US 50 and above 7000
feet.
&&
.DISCUSSION...
...Today-Saturday AM...
Mostly sunny skies with a few high clouds being observed today
across NorCal. Today is expected to be the last day of above-
normal temperatures before we cool down this weekend.
The upper level pattern changes tonight as a PacNW trough and
weak closed low form offshore. The resulting pressure gradient
will produce gusty west to southwest winds tonight through
Saturday, strongest through the Delta and gaps in the Coast
Range, but up into the Sacramento Valley as well. Forecast wind
gusts around the Delta are up to 45 mph with sustained winds 20 to
30 mph. As a result a Wind Advisory has been issued for the Delta
and immediate vicinity Valley locations and is in effect from 11
PM tonight until 7 AM Saturday morning. Gusts through the rest of
the Valley will be closer to 25-35 mph. Strongest winds are
expected late tonight-early morning hours. Gap flow winds in the
Coast Range and Sierra crest will also experience gusts close to
40-45 mph.
...Saturday (rest of)-Monday...
Gusty winds will continue through most of Saturday and we will
see our first day of more fall-like high temperatures across
interior NorCal. Highs are expected to be in the mid to upper 70s,
low 80s in the northern San Joaquin Valley.
A cold system dropping down from the PacNW will phase with a weak
offshore low, bringing chances for the first measurable snowfall
of the season in the Sierra Sunday PM-Monday. Snow levels are
expected to remain above 7500 feet through Sunday, before lowering
between 7000-7500 feet Sunday night into Monday. Forecast amounts
are between 0.5-4 inches above 7000 feet, with 2-4 inches possible
at the highest peaks. There is still a decent amount of
uncertainty regarding the track of this system and forecast
amounts, but confidence is high that we will see measurable snow
from this event in the high Sierra.
Additionally this system will bring wetting rain to the Sierra and
foothills (but mainly the Sierra), chances for isolated
thunderstorms Sunday and Monday, and continued gusty winds.
Recent ensemble runs are continuing to keep the bulk of tropical
moisture south of our warning area. Some moisture advection will
nose into portions of the Sierra Nevada, mainly on Sunday and
Monday. Right now, best chances of seeing 0.50" of rain remains
above roughly 3000 feet and south of I-80. With the path of the
trough and an eventual low pressure developing/closing off,
isolated t-storms will be possible in the higher elevations Sunday
and Monday as well. While the NBM keeps probabilities at or below
15%, location of the aforementioned low will provide the lift,
cold air/instability aloft to produce t-storms if enough moisture
advects.
Winds will be onshore for most of the day on Saturday, before
shifting out of the north Sunday-Monday. North winds are forecast
to gust 30 to 40 mph, with the strongest winds along and west of
the I-5 corridor. While overnight recoveries and daytime
humidities will be increasing, the drying north winds will bring
Elevated Fire Weather conditions to the northern Sacramento Valley
and adjacent foothills.
This system is also expected to bring cold temperatures to the
mountains, with overnight temperatures in the low 20s to mid 30s
in the Sierra this weekend and into early next week.
...Tuesday-Thursday...
By Tuesday, the aforementioned closed low begins to translate
eastward, with continued below-normal temperatures on Tuesday.
Ensembles depict offshore ridging developing by Wednesday and
Thursday, suggesting high temperatures will climb back into the
low to mid 80s by the middle to late next week.
&&
.AVIATION...
VFR conditions continue across interior NorCal next 24 hours.
Surfaces winds for WNW at 5-10 kts for KSCK and KMOD, while SW
winds at 5-15 kts for the reminder of the forecast terminals.
Breezy conditions with gusts up to 20 mph are expected to
developed after 09/20Z in KRDD. Winds will ease across the
northern terminals this evening, while become breezy for the
airports in the Sacramento Area after 10/05Z with gusts from 20-25
mph possible through Saturday. &&
.STO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 11 PM this evening to 7 AM PDT Saturday for
C. Solano County including Fairfield-SW Solano County including
Vallejo.
&&
$$
