931
FXUS66 KSTO 021954
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1254 PM PDT Wed Sep 2 2026

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



.KEY MESSAGES...

  - Well below normal temperatures persist through this week

  - Wet weather continues this week, thunderstorms and scattered
    showers, scattered showers for mainly Shasta County today,
    becoming widespread north of I-80 Thursday

  - Showers continue on Friday over the Sierra and southern
    Cascades and adjacent foothills

  - Mainly dry Saturday, with some mountain showers Sunday, mainly
    north of I-80

  - There is the potential for some remnant tropical system
    moisture next week, but confidence in details remains low at
    this point

&&

.DISCUSSION...

Today...

Showers last night brought moderate to locally heavy rain in
Shasta County as a shortwave trough moved through, with rainfall
amounts ranging from around a quarter of an inch to locally nearly
an inch over the mountains in the northern portion of the county.
Another wave is spreading some showers into Shasta County this
afternoon, and these will become more widespread overnight, north
of I-80. Elsewhere today there has been dry weather with low and
mid level clouds and cool temperatures. Forecast high temperatures
for today 10 to 30 degrees below normal, ranging from the low 70s
in the northern Sacramento Valley to the low 80s in the northern
San Joaquin Valley. Some breezy onshore winds continue today into
tonight, south to southwest winds, with gusts to around 20 mph in
the Valley and Delta, up to 30 to 40 mph in the mountains.

Thursday to Early Next Week...

The remainder of the week and into the weekend, troughing will
remain the dominant pattern, maintaining cooler than normal
temperatures and bringing more widespread precipitation. Most of
the precipitation has trended to be on Thursday, with confidence
and forecast rainfall amounts increasing for areas north of I-80,
including into the Sacramento Valley. The latest storm totals
have trended higher in those areas, ranging up to an additional 2
inches over the mountains of northern Shasta County, with the
northern Sacramento Valley seeing a quarter to a half of an inch.
Forecast amounts elsewhere in the Valley and Delta have trended
lower, generally a tenth of an inch or less. Main impacts will be
slick roads, especially with oil building up over the summer. There
continues to be a 15-20% probability of thunderstorms Thursday in
the mountains north of I-80, highest over the mountains of Shasta
County and western Plumas County. An upper low spinning centered
over Oregon may have bring some weak disturbances in the mountains
over the weekend, but Saturday has trended dry. On Sunday the
center of the upper low passes along the California and Oregon
border, with slight chance of mainly Shasta County showers,
generally dry elsewhere.

There is still some potential for a tropical system to bring some
moisture into California next week, but confidence in
precipitation potential from this extending into interior Northern
California remains fairly low and now looks more likely mid next week.
Currently the best potential for rain is over the mountains south
of I-80 on Wednesday, especially in the mountains. Temperatures
trend warmer, to near normal by Wednesday.

&&

.AVIATION...
VFR conditions prevail over the next 24 hours across interior
NorCal. Valley south to west 10 to 15 kts in the afternoon with
gusts up to 20 to 30 kts and Sierra gusts up to 35 to 40 kts until
03z Wednesday with lingering gusts over the northeast foothills
and Sierra through 12z Thursday. &&

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

$$