629
FXUS66 KSTO 281913
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1213 PM PDT Fri Aug 28 2026

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

.KEY MESSAGES...

  - Seasonable to below normal temperatures persist through the
    weekend and into next week.

  - Elevated Fire Weather conditions from dry and breezy weather
    north of Interstate 80 and isolated mountain thunderstorms in
    the Sierra south of Interstate 80 through this evening.

  - Shower and isolated thunderstorm chances continue south of
    Interstate 80 today, with drier weather through at least early
    next week.

  - There is high uncertainty in exact details, but unsettled
    weather and precipitation chances look to return by late next
    week.

&&

.DISCUSSION...

Today...

A quick peek at satellite shows troughing largely centered
offshore of the Bay Area early this afternoon. This is allowing a
rather deep plume of subtropical moisture to filter across
interior NorCal today as evidenced by a persistent cloud shield
spanning from Stanislaus County up through Shasta County. As a
result, high temperatures today are expected to end up around 10
degrees cooler than Thursday. Breezy onshore winds do look to
increase through the afternoon with strongest gusts 20-30 mph
anticipated in the northern Sacramento Valley/Burney
Basin/northeast Foothills. Despite the influx of moisture aloft,
daytime humidity values in the teens to lower 20s in the above
areas, in conjunction with the breezy winds, will continue to
introduce Elevated Fire Weather conditions through this evening.

With the moisture plume and more notable forcing from the
offshore trough centered further southward, light showers and
virga are being observed generally along a line from Interstate 80
southward. This is expected to remain the case throughout the
day, although some areal expansion toward the Highway 36 corridor
is possible this afternoon. Even with the moisture rich
environment aloft, persistent cloud cover is limiting diurnal
heating and available instability with thunderstorm chances
looking to become increasingly confined to higher elevations
today. Resultant probabilities of thunderstorm development remain
around 20-40% along the Sierra south of I-80. As for accumulating
rainfall, Valley/foothills probabilities sit around 10-20% for
0.01" with probabilities for greater than 0.25" around 40-70%
along the Sierra.

This Weekend Into Next Week...

As the moisture plume pushes eastward heading into the weekend, a
trend toward drier weather is anticipated area wide Sunday into
early next week. While chances are expected to be notably lower on
Saturday, there may be enough overlap of lingering moisture and
troughing aloft for additional shower/thunderstorm potential along
the Sierra south of Highway 50. At this time, probabilities of
showers and isolated thunderstorms sit around 10%, although
highest potential will likely be from the Sierra crest eastward.
Despite the broader drying trend that is on track late weekend
into early next week, the presence of a troughing aloft and low
heights will keep temperatures seasonable through the weekend.

By early next week, ensemble guidance is in general agreement on
a longwave trough deepening offshore of the Pac NW toward NorCal.
The immediate impacts of this developing pattern look to be even
further cooling to widespread below normal temperatures and highs
in the 70s to 80s for much of the week. There is some potential
for early morning low temperatures nearing the freezing mark above
7000 feet by midweek as well. Periods of breezy onshore winds
will likely accompany the cool down around Monday-Tuesday, with
gusts 25-35 mph possible at times through the Valley and Delta.
There continues to be notable ensemble uncertainty on the
potential for a return to unsettled and active weather later next
week. While additional chances for precipitation remain possible,
the timing and location of attendant moisture complicates the
forecast at this time.

&&

.AVIATION...
Active weather continues across interior NorCal today with -SHRA
and isolated thunderstorm chances from Interstate 80 southward
through 03z Saturday. Despite this, VFR conditions are expected to
prevail, although reductions to brief MVFR conditions will be
possible in any thunderstorms that develop. Otherwise breezy to
gusty south to west winds are expected through 03z Saturday, with
strongest gusts 20 to 25 kts in the northern Sacramento Valley and
surrounding terrain as well as through the Delta.

&&

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

$$