705
FXUS66 KSTO 212017
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
117 PM PDT Mon Sep 21 2026



.KEY MESSAGES...

  - Periodically breezy winds and warming temperatures, peaking
    on Thursday with areas of Moderate HeatRisk in the Valley.

  - Isolated mountain shower and thunderstorm chances (less than
    10%) today along the Sierra Crest.

  - Potential for unsettled weather and increased onshore winds
    over the weekend as a system passes to our north.

&&

.DISCUSSION...

...Today through Thursday...

Scattered clouds continue to move across parts of northern
California today, with cooler temperatures and breezy onshore
winds. Highs today reach into the low to mid 80s across the
Valley, with cooler temperatures at higher terrain. Breezy
conditions at times within the Delta and near the Sacramento Metro
this evening. Otherwise, a lingering short wave is pushing
instability and moisture into the mountains today bringing the
slight chance for an isolated shower or storm. Chances are highest
along and south of Highway 50 along the Sierra Crest, with lower
chances through the southern Cascades. Radar currently has storms
developing west of Mono County and south of the forecast area.
Main time frame for chances in the Sierra and southern Cascades
is around 3-8pm before instability and forcing is lost. Dry
conditions are expected on Tuesday with continued cooler
conditions. Tuesday morning we could see lower clouds develop in
the Bay area and shift into the Sacramento Metro and spread into
Yuba City and parts of Stockton. This would lower ceilings and
bring a BKN to OVC cloud deck through the morning hours. This
wouldn`t last long as after sunrise the clouds will burn off.

Conditions will continue to dry out Wednesday through Thursday,
with temperatures reaching back into the upper 80s Wednesday and
the low to mid 90s on Thursday. Areas of Moderate HeatRisk are
possible for parts of the southern Sacramento Valley and into the
northern San Joaquin Valley Wednesday and Thursday. The highest
chance for Moderate HeatRisk will be on Thursday in the northern
San Joaquin Valley.

...The Weekend Ahead...

Heading into the weekend our pattern begins to evolve and change
across the area. Stronger onshore winds are looking more
probable, with cooling temperatures. Confidence remains low, but a
system looks to translate across parts of the Pacific northwest
bringing increased moisture, instability, and forcing to the area.
The development, timing, and the track of the system are in
question as guidance struggles to show exactly where we could see
precipitation. None the less, we will be watching for the pattern
change and any potential for an unsettled weather pattern over
the weekend and into early next week.


&&

.AVIATION...

VFR conditions are expected through the remainder of today and
into tonight. SCT clouds are affecting the Sacramento sites along
with SCK and MOD. Around 11-13z marine layer clouds shift into the
region bringing BKN to OVC clouds. Confidence is low on if
ceilings reach MVFR or remain VFR. As of right now we are looking
at 3000 foot ceilings for the Sacramento sites tomorrow morning
through the end of the TAF period. Otherwise, winds will be breezy
at times this afternoon near the Delta.


&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$