777
FXUS66 KSTO 162145
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
145 PM PST Tue Dec 16 2025

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

.KEY MESSAGES...

 - Series of weak atmospheric rivers expected through the weekend,
   with periods of rain, gusty southerly winds, and high snow
   levels.

 - Potential for wetter storms on the horizon for the week of
   Christmas, details remain uncertain this far out.

&&

.DISCUSSION...

...Today through Monday...

Lower stratus is breaking apart giving away to some quick sunshine
in parts of the Central Valley. Current radar has scattered rain
moving across the Coastal range through the southern Cascades and
reaching down into the northern Sacramento Valley. Rain should
predominately remain north of I-80 this afternoon and evening,
with a slow shift east and south Wednesday. Rain will be
widespread Wednesday, with higher amounts over the Sierra, Coastal
range, and southern Cascades. Thunderstorm chances increase this
evening and overnight across the Sacramento Valley and adjacent
mountains as instability increases. Probabilities are around 10 to
25 percent, with the highest over the Sierra and Coastal range.
Further chances for rain and beneficial rain as we move into the
weekend. Chances for moderate to locally heavy rain for areas
along and north of I-80 Saturday into Sunday. There will be a
chance for accumulating snow within the mountains, with
probabilities of 4 inches or greater ranging from 25-50 percent
around Lassen and the higher peaks in the Sierra Saturday into
Sunday. Snow levels start out around 8000 feet Saturday and
gradually fall toward 7000 feet by Monday. Highest snow totals
will be over 8000 feet.

Along with the precipitation there will be the higher winds
through the Valley and in the mountains. Gusts up to 35mph Friday
through Monday for areas within the northern Sacramento Valley
and adjacent mountains. Other than the precipitation and winds,
temperatures will be in the 50s across the area through the
weekend and into Monday.

...Next Week...

As the ridge over the eastern Pacific and southwestern United
States continues to break down, several chances for upper level
waves increases through Christmas week and potentially beyond. Current
long range guidance highlights the active pattern with a trough
digging into the eastern Pacific pumping moisture, instability,
and synoptic forcing into CA. Uncertainties with the exact timing,
development of systems, and exact track at this time. Continue to
monitor the latest forecast as we move into the holiday week and
into the New Year.

&&

.AVIATION...

Ceilings have improved since this morning for all sites. RDD and
RBL are sitting around 4-6SM while other sites are P6SM. Ceilings
remain IFR and briefly reach MVFR at times this afternoon as rain
continues to move through RDD, RBL, and portions of the Sacramento
area. Rain continues throughout today and into tomorrow. Ceilings
will be around IFR to MVFR through the TAF period. Widespread
rain chances end of the TAF period and through Wednesday for all
TAF sites. Light and variable winds through tomorrow morning
before turning south at 10-15kts.

&&

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

$$