823
FXUS66 KSTO 022033
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1233 PM PST Fri Jan 2 2026

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


.KEY MESSAGES...

 - Major mountain travel impacts above 5000 feet this weekend with
   white out conditions at times.

 - Heavy rain, isolated thunderstorms, and gusty winds this
   weekend. Urban and small stream flooding may result from heavy
   rains.

 - Drier weather returns Tuesday, with active weather mid to late
   week.

&&

.DISCUSSION...

...Today through Monday...

Conditions remain dry for a majority of the area today, with a
few showers near the northern Sacramento Valley and Coastal Range
locations. As we move into the evening hours the first main wave
of precipitation begins to move onto the coast and into the
forecast area. Rain will become widespread, with intensity being
moderate to heavy at times. Surging instability and moisture into
the area will help fuel the higher rainfall rates up to an inch
per hour within the foothills and near Shasta County. Snow levels
at this time are 6500-7500 feet and drop through the overnight and
into tomorrow.

There will be a brief break in activity within the Valley
tomorrow morning while areas in the mountains continue to see
widespread precip. A secondary wave of precipitation moves through
increasing the instability toward 500 J/k MUCAPE, low level
shear, and moisture transport. This will help fuel thunderstorm
chances within the foothills and Valley. HIRES guidance has
started to pick up on a convergence zone developing in Shasta
County tomorrow afternoon, however, there is disagreements on
exactly where and how long it will last. None the less, when this
convergence zone develops we have the potential to see high
rainfall rates which may lead to flooding concerns. There will be
an isolated threat for strong to severe thunderstorms tomorrow
afternoon and evening, with hail, gusty winds, and a brief tornado
possible. Snow levels drop Saturday afternoon to 5000-6000 feet
as colder air wraps around the upper level low moving onshore.
Heavy snow is expected, with white out conditions at times. Winds
will be strong out of the south to southwest, with gusts up to
55mph in the mountains. Snow accumulation will range between 1-2
feet between 5000-6000 feet, and 2 to 5 feet above 6000 feet.
Locally higher amounts at the peaks. A winter Storm Warning is
effect for the Sierra this evening through Monday for the heavy
snow and strong winds. If you plan to travel make sure you have
alternate routes, backup plans, and carry a safety kit with you at
all times.

Moderate to heavy rain will continue to affect the Valley and
foothills Sunday and again on Monday. A Flood Watch was issued for
areas below 4000 feet in the Coastal Range, Shasta County, Sierra,
and Sacramento Valley from 10pm this evening through 4pm Monday.
Forecasted rainfall at this time is 1-3 inches in the Valley and 3
to 5 within the Foothills up to 4000 feet. Lower rainfall is
expected in the Delta and northern San Joaquin Valley and thus
where not included within the watch. There is uncertainty with the
exact rainfall amounts as influencing factors from thunderstorms
could bring up totals slightly.

Otherwise, as the waves of precipitation move onshore and through
the area winds will be increasing out of the south to southwest in
the foothills and Valley, with gusts of 35-45mph for the northern
Sacramento Valley and adjacent foothills. Other areas within the
Valley and foothills will see gusts from 25mph to 35mph.

...Tuesday Onward...

Lingering mountain snow showers late Monday into Tuesday morning,
however conditions dry out briefly during the day on Tuesday.
Next chance for precipitation comes mid to late week as another
system moves through the eastern Pacific towards CA. Uncertainty
with exact timing, how impactful, and its track.

&&


.AVIATION...

A few showers continue to affect RBL and RDD today, with more
widespread rain chances as we move into the evening around 23-02z
for each site. Rain will be moderate to heavy at times with
visibilities fluctuating between 2SM and 6SM. Low ceilings
combined with the rain as it moves through. A slight lull in
coverage during the early morning hours around 12-17z tomorrow
before another round post TAF period, with chances for
thunderstorms.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Flood Watch from 10 PM PST this evening through Monday afternoon
for Central Sacramento Valley-Motherlode-Mountains Southwestern
Shasta County to Western Colusa County-Northeast
Foothills/Sacramento Valley-Northern Sacramento Valley-Shasta
Lake Area / Northern Shasta County-Southern Sacramento Valley.

Wind Advisory from 10 PM this evening to 4 AM PST Sunday for
Central Sacramento Valley-Northeast Foothills/Sacramento Valley-
Northern Sacramento Valley.

Winter Storm Warning from 10 PM this evening to 4 PM PST Monday
for West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.

&&

$$