501
FXUS66 KSTO 252146
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
204 PM PDT Sat Oct 25 2025

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

.KEY MESSAGES...

 - An atmospheric river storm will continue to bring beneficial
   rain showers, light high elevation snow, gusty winds, and
   cooler temperatures through Sunday. The majority of rainfall is
   expected from Interstate 80 northward. Isolated thunderstorms
   possible in that area Saturday afternoon and evening.

 - Dry and seasonable weather returns Monday and is expected to
   continue through the week.

.DISCUSSION...
Today - Sunday...A trough from the Gulf of Alaska is passing
through the Pacific Northwest and Northern California and
combining with moisture from an atmospheric river spreading from
the eastern Pacific. Most of this system is focused to the north,
with scattered showers developing over portions of interior
Northern California today, especially over the mountains and
foothills north of I-80. There is a 15-25% chance of isolated
thunderstorm development into this evening for the northern
Sacramento Valley and nearby terrain. The best potential for this
thunderstorm activity is over Shasta and northern Tehama
counties, with a narrow band of heavy rain moving through early to
mid afternoon. A brief lull in shower intensity is expected late
this evening before the next wave of scattered showers returns by
early Sunday. These continue through the day Sunday mainly north
of Interstate 80 in the mountains and foothills and extend into
the northern Sacramento Valley. Gusty southerly winds peak over
the northern and central Sacramento Valley continue this afternoon
with gusts up to 40 mph before diminishing early this evening.
Breezy winds will pick up through the day Sunday but not as
strong, with local gusts up to around 25-30 mph over the northern
Sacramento Valley and to 35 mph over the higher mountains. Sunday
morning there is some patchy fog possible (35-65% chance) over the
northern San Joaquin Valley, diminishing by late morning.

Monday - Saturday...Broad northwest to zonal flow is looking
likely into next week as the trough exits the region and upper
level ridging builds in with near to slightly above normal
temperatures and dry weather. Periods of breezy north to east
winds are expected early in the week, with gusts 15 to 20 mph
possible at times, locally stronger in canyons and over mountain
ridges. /EK


.AVIATION...
A weather system will continue to bring scattered showers through
Sunday, with MVFR/IFR conditions. Isolated thunderstorms possible
across the northern Sacramento Valley and adjacent terrain until
00z Sunday. Surface winds generally less than 12 kts through
tonight. Gusty south to southwest winds until 03z Sunday, with
gusts up to 15-35 kts in the Sacramento Valley and up to 20-35 kts
over the mountains. Another round of breezy south to southwest
winds after 15z Sunday, with gusts up to 15-20 kts in the
Sacramento Valley and up to 20-25 kts over the mountains. Patchy
dense fog possible across the northern San Joaquin Valley 10-17z
Sunday, with MVFR/local IFR conditions. &&

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

$$