031
FXUS66 KSTO 172044
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1244 PM PST Mon Nov 17 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 remains in effect until 4PM Today for
   elevations 6000 feet and above in the Sierra/Southern Cascades.
   Additional snow accumulation of 2 to 6 inches; with up to 8
   inches at the highest peaks with wind gusts of 20-30 mph.
 - Scattered rain showers with 10-20% chance of t-storms this
   afternoon and evening.
 - Drier conditions return Tuesday into Wednesday morning,
   followed by another weather system late Wednesday into Friday.

.DISCUSSION...

...This Afternoon through Wednesday Evening...
Late this morning, we saw scattered showers over the Sierra and
adjacent foothills as the upper level low tracks down the Sierra.
We can expect conditions to taper off throughout the evening with
rain showers persisting over the Sierra south of Interstate 80
and over the Coastal Range/N. Sacramento Valley. Latest forecast
show a 10-20% chance of thunderstorms this afternoon and evening,
highest along the western portions of our Valley. As the low
rotates through the evening showers could move over the Delta
region but storms should be dying out if it makes it to the area,
Additional rain totals of a quarter of an inch across much of the
area and up to a half inch over the Coastal Range and Sierra,
south of Hwy. 50. For snow, elevations above 6000 feet may see an
additional 2-4 inches, up to 8 inches over the mountain peaks.

Overall looking at the morning run of hi-res data, areas below
3000 feet could see a pop-up shower or two as the system continues
to swing through the area but more often than not these showers
will be closer to short burst of higher rain rates and occasional
lightning than anything significantly organized convection wise.
By Tuesday morning, we will enter a brief lull in weather into
Wednesday with mild conditions and highs in the upper 50s to low
60s in the Valley.

...Wednesday Evening - Friday...
The trough is currently forecast to bring renewed rain and
mountain snow chances late Wednesday through Friday afternoon.
Latest NBM runs have increased total rain and snow for our region
slightly, but still within the same impact range as yesterday`s
package.

Recent trends show a increase in available moisture for the
event, however resulting forecasted rain and snow amounts still
look to be minor impacts if any. NBM probabilities show a 30-50%
chance of 3 inches or more over the Sierra above 6000 feet and
30-60% chance of 0.25" of rain of more for the Valley so even
amidst the uncertainty the system looks to be on the lower range
of impacts, if any. Rain and snow should taper off Thursday
evening into Friday morning as dry weather returns.

...Next Weekend - Early Next Week...
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 through the
weekend. Monday brings an outside chance of weak showers over the
Sierra and N. Sac Valley but chances remain low and impacts look
minimal.


.AVIATION...

Widespread VFR with isolated areas of MVFR due to lingering
showers. Isolated thunderstorms from 21Z Monday until around 00z
Tuesday, mainly across portions of the Delta and western Valley.
Southerly wind gusts 15 to 25 knots in the Valley and Delta,
through 00z Tuesday. Snow levels around 5000-6000 feet by Monday
morning. Chances for MVFR/localized IFR conditions tomorrow
morning due to mist and low stratus along the western Valley from
12Z to 17Z Tuesday.
&&

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

&&

$$