584
FXUS66 KSTO 152139
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
139 PM PST Mon Dec 15 2025

For additional details on weather and expected impacts over the
next 7 days, please visit weather.gov/sto/briefing.


.KEY MESSAGES...

 - Fog, mist, and low clouds for the Central Valley, Delta, and
   adjacent foothills continues tonight into early Tuesday.

 - High temperatures in the Central Valley, Delta, and lower
   foothills will gradually trend to more mild levels by the
   middle of the week.

 - Series of disturbances will bring periods of beneficial rain,
   breezy south winds and isolated thunderstorms at times from
   Tuesday into the weekend.

 - Active weather pattern continues into next weekend, including
   the holiday travel period, though details remain uncertain.

&&

.DISCUSSION...

...Today - Tonight...

Latest satellite imagery continues to show the low stratus deck
and patchy fog across the Central Valley and adjacent foothills.
A few areas in the northern Sacramento Valley have clear out and
temperatures to warm, while the low clouds linger elsewhere.
Temperatures underneath the stratus have been well below normal
for highs, and areas above the stratus continue to be above
average. A disturbance over the Pacific Northwest brushes through
far Northern California tonight, bringing some scattered showers
to the northern Coastal Range and Shasta County. Dense fog may
continue overnight into Tuesday morning, with visibility
reductions to a quarter mile or less for areas within the Central
Valley.

...Tuesday - Thursday...

An upper level wave moves in Tuesday increasing precipitation
chances and breezy conditions to the region. Look for continued
low ceilings, mist, and foggy conditions Tuesday morning.
Precipitation spreads southward through Tuesday, but remains
along and north of the I-80 area for the day, then over much of
the rest of the area Tuesday night. Coverage will be isolated for
the showers for much of Tuesday. By the afternoon instability and
moisture increase across the forecast area giving way to
thunderstorm chances, though these have trended lower, now 10-15
percent across the area. Best chances will be within the Sierra,
Motherlode, Sacramento Valley, and Coastal Range. Coverage will be
scattered to widespread across the area for precipitation. With
snow levels above 8000 feet, no impacts are expected. A brief
lull in precipitation is expected Thursday morning and afternoon,
before another round of precipitation moves into the region
bringing breezier conditions.

...Friday Onward...

An active pattern continues for Friday and into the weekend, with
another upper level wave moving out of the eastern Pacific. This
system has trended cooler over the past couple of runs of the NBM.
Snow levels have trended a little higher and are looking to be
above 7500 feet by Friday afternoon and evening and remaining so
through the weekend, which has reduced forecast snowfall amounts
and should limit travel impacts. Moisture content has trended
higher with the system, with chances for widespread largely
beneficial precipitation. Breezy conditions are expected with the
system as it moves through the area. Confidence remains low on
the full development, track, and snow levels with the system,
especially into next week. Stay tuned for details!

&&


.AVIATION...

Low ceilings and visibilities continue for areas within the
Central Valley. Clearing has been observed near RDD and RBL this
afternoon, which will be short lived. By this evening stratus will
move back into the northern Sacramento Valley, with increasing
chances for precipitation. Areas around Sacramento and the San
Joaquin Valley will continue to see low stratus and foggy
conditions throughout today. Some improvements to the ceilings and
visibilities this afternoon before conditions deteriorate again
later this evening and overnight. Light and variable winds are
expected through the TAF period.

&&

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

$$