011
FXUS66 KSTO 302040
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1240 PM PST Tue Dec 30 2025

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



.KEY MESSAGES...

 - Dry conditions through early Wednesday, with low stratus and
   foggy conditions.

 - Moderate travel impacts late week and into the weekend, from
   heavy mountain snow and wind. Minor travel impacts for the
   foothills and valley.

 - Unsettled weather pattern continues into next week.

&&

.DISCUSSION...

...Today through Wednesday...

A ridge continues to dominate across the southwestern United
States keeping conditions dry. Under the ridge winds have been
light and variable allowing for fog and low stratus to develop in
the evening and continue through the morning hours. Visibilities
have been lowest in the Sacramento Metro area and down through
Modesto. Areas in the northern Sacramento Valley have seen
visibility reductions, but not as widespread. Above 1000 feet
conditions are mostly sunny today before higher level clouds move
in this evening.

Overnight we expect fog to redevelop and become patchy. Confidence
remains low on how widespread the fog gets and how dense it
becomes overnight as a system begins to slowly push into the
region for Wednesday and Thursday. This will help keep some of the
fog less dense in places. By Wednesday afternoon, a system from
the eastern Pacific begins to shift into the southern forecast
area bringing increased precipitation chances. Rain will become
widespread through Wednesday night and continue into Thursday.
Otherwise, temperatures will be cooler on Wednesday, with highs in
the upper 40s to lower 50s for the Valley. Areas in the foothills
will see the mid 50s.

...Thursday through Sunday...

Rain continues to move through the area on Thursday, with a brief
lull in coverage for the Valley during the late afternoon and
evening hours. Precipitation coverage increases Friday morning and
continues throughout the day. As the main trough moves closer to
the CA coastline, the feed of moisture and instability into the
region increases. This brings the chance for thunderstorm activity
Friday afternoon through early Saturday morning for the Valley
and foothills. Forecasted rain amounts range from 1-3 inches, with
locally higher amounts possible Thursday through Sunday
afternoon.

Snow levels remain high on Thursday around 7500-8500 feet and
above, but begin to drop by the evening and overnight hours
reaching 6500-7500 feet by Friday afternoon. Snow levels reach
5500-6500 feet and above Friday night and into Saturday, with snow
becoming heavy at times. Probabilities for over 20 inches is
60-70 percent for areas within the Sierra from Friday evening
through Sunday afternoon. Winds will also be strong in the Sierra,
with gusts up to 45 mph during this timeframe. There still
remains some uncertainty with how fast snow levels drop as
temperatures aloft cool. Uncertainty also arises with the amount
of moisture moving into the region. Accumulations are uncertain at
this time but may range from 1 to 3 feet above 5500 feet. Locally
higher amounts are possible at higher elevations. We have issued
a Winter Storm Watch for our Sierra zones for the heavy snow and
windy conditions. If you plan to travel this week and into the
weekend, make sure you have alternate routes, backup plans, and
carry a safety kit with you at all times.

Long range guidance looks to continue the feed of moisture and
instability into the region early next week bringing further
precipitation, mountain snow, and breezy conditions.

&&


.AVIATION...

LIFR/IFR ceilings continue through 23z for low stratus and foggy
conditions. Ceilings improve slowly this evening, but fog and low
stratus move back in overnight dropping ceilings and visibility.
Morning fog and low stratus 6z through the end of the TAF period
for each site. Winds will be light and variable through the TAF
period. Beyond the TAF period, precipitation moves in from the
south by Wednesday evening.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Friday afternoon through Sunday morning
for West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.

&&

$$