886
FXUS66 KSTO 162032
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1232 PM PST Sun Nov 16 2025

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


.KEY MESSAGES...

 - A Winter Weather Advisory is in effect until 4PM Monday for
   elevations 6000 feet and above in the Sierra/Southern Cascades.
   6 to 12 inches; with 1-2 feet at the highest peaks with wind
   gusts of 40 mph.
 - Mostly light rain showers in the area this afternoon. Lull in
   activity expected to continue until later this evening/tonight.
 - A colder system will bring more widespread rain and moderate
   mountain snow tonight into Monday. Breezy southerly winds will
   accompany the system, along with isolated thunderstorms on
   Monday.
 - Drier conditions return Tuesday into Wednesday morning,
   followed by another weather system late Wednesday into Friday.

.DISCUSSION...

...Today through Tuesday Morning...
Upper level low in SoCal continues to traverse eastward this
afternoon, with another trough in the PacNW following closely
behind. Water vapor satellite imagery reveals a low level dry
slot currently making its way inland over the Coastal Range with
abundant moisture following along the aforementioned trough axis.
Scattered showers, mainly in the mountains and foothills will
continue before main trough moves inland and again brings renewed
Valley rain, thunderstorm chances tonight and tomorrow. PacNW
trough is much cooler than the initial wave yesterday and early
this morning, where snow levels were at and above pass levels.
Once colder air overtakes the higher terrain, moderate snow will
develop and continue through Monday evening. As such, a Winter
Weather Advisory is in effect until 4 PM Monday, where 6 to 12
inches of snow is expected at 6000 feet, with 1-2 feet likely at
the higher peaks. Gusty southerly winds 30-40 mph may also
accompany the arrival of this system; with increasing confidence
that some of the stronger gusts may also impact areas in the
northern Sacramento Valley tonight/early tomorrow morning. Hi-
resolution models such as the HRRR also depict a surface low
moving over the Valley tomorrow, which will further increase our
chances for an isolated thunderstorm with the best chances in the
central/southern Sacramento Valley and Delta. A surface low over
the area will enhance what limited instability will be present as
trough axis pushes through, so it is not out of the question a few
rumbles of thunder will be possible tomorrow morning through the
afternoon. By late Monday night into Tuesday morning, surface low
digs further south, allowing for drying and a small increase in
afternoon high temperatures. The pattern quickly changes back into
an unsettled regime, as another PacNW trough is progged to dig
into the region by Wednesday night/Thursday morning.

...Thursday and Friday...
The trough is currently forecast to bring renewed rain and
mountain snow chances Thursday through Friday afternoon. Latest
NBM runs have increased total rain and snow for our region, a
change from last night`s forecast package. Confidence remains very
low on exact track of the trough and a potential surface low in
the area, so exact precipitation totals or any potential
convection are still fuzzy at this time. Regardless, it appears
this trough will move further east by Friday, following a quasi-
inside slider pattern, so north winds are in the forecast,
although nothing strong or concerning at this time. Current snow
levels for this system appear to be in the 5500+ range, the big
question will continue to be how the track and available moisture
will play out. Valley rain currently looks to be lower than 0.50"
inches, except in Shasta County where higher totals are forecast,
especially in the Shasta Lake watershed area.

...Next Weekend...
Drier weather overtakes the area by Friday night, as upper level
ridging is progged to develop and somewhat strengthen in the
eastern Pacific. Weak troughing to the north in/near the Gulf of
Alaska may help keep our heights flat, with seasonable high
temperatures and mainly dry weather in the forecast.

.AVIATION...

Areas of MVFR/IFR conditions, locally IFR, will become more
widespread this evening through tomorrow as another system moves
through the area. Isolated thunderstorms possible after 03z-06z
Monday until around 00z Tuesday, mainly across portions of the
Delta and Valley. Southerly wind gusts 15 to 30 knots in the
Valley and Delta, locally up to 35 kts through 00z Tuesday.
Southwesterly wind gusts up to 20-35 kts over higher terrain
through 00z Monday. Snow levels around 6500-7000 feet, lowering to
around 5000-6000 feet by Monday morning.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 4 PM PST Monday for West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.

&&

$$