035
FXUS66 KSTO 082048
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
148 PM PDT Sat Aug 8 2026

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


.KEY MESSAGES...

 - Heat Advisory in effect through 10 PM Sunday for the Sacramento
   and San Joaquin Valleys, Sierra foothills, and mountain
   locations north of Highway 50.

 - Widespread high temperatures in the 90s to triple digits and
   warm overnight lows result in Moderate to Major HeatRisk
   through the weekend. Gradual cooling trend expected next week.

 - Elevated Fire Weather Conditions in the northern Sacramento
   Valley, Burney Basin, Sierra, and adjacent Foothills through
   Monday due to hot temperatures, low humidities and increased
   breezes.

 - Isolated thunderstorm (15%) chances along the Sierra Crest
   south of Interstate 50 through the weekend.

&&

.DISCUSSION...A broad upper-level ridging centered over the Four
Corner will continue to dominate the weather pattern for interior
NorCAl through Sunday. Temperatures will peak today and Sunday,
with widespread triple digit high temperatures across the Valley
and foothills and overnight low temperatures in the mid 60s to
70s. With resultant widespread Moderate HeatRisk and areas of
Major HeatRisk across interior NorCal. A Heat Advisory remains in
effect through 10 PM Sunday for the Valley and foothills, as well
as mountain locations north of Highway 50.

While hot and dry weather is expected to persist across the
region, monsoonal moisture streaming from the SW along the
western periphery of the ridge. Models suggest an increase in
instability for today and Sunday, resulting in a 15% chance for
afternoon thunderstorms along the Sierra crest south of Highway 50
through the weekend as well. Potential hazards with any
thunderstorms that develop will be lightning, gusty winds, and
possible new fire starts. Elsewhere, as the upper level pattern
continues to limit onshore flow magnitude, low daytime humidity
into the teens and single digits alongside limited to poor
overnight humidity recovery will lead to a continuation of
elevated fire weather conditions through Monday as well.

Early next week, a mid- to upper-level shortwave trough develops
off the West Coast, while the ridge slowly breaks down through
middle week. Onshore flow is expected to increase in response,
providing a broader overnight relief and increasing humidity
values. The heat is expected to gradually recede early through
mid next week, with lingering Moderate HeatRisk through Wednesday.

Ensembles continue to suggest the upperl-level trough settles over
the region, bringing more widespread cooling, with near to below
normal temperatures and a decrease to Minor HeatRisk area wide.
Additionally, there are some signals within ensemble guidance for
a subsequent surge of monsoonal moisture that may introduce
mountain thunderstorm chances back to the forecast by late next
week.


&&

.AVIATION...


VFR conditions are expected to prevail over the next 24 hours.
Winds generally remain 12 kts or less at TAF sites. West to
southwest gusts up to 20-25 kts in the Delta from 00Z through 12Z
Sunday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 10 PM PDT Sunday for Burney Basin-Butte
County Below 1000 ft-C. San Joaquin County including Stockton-C.
Stanislaus County including Modesto-C. Yolo/NE Solano including
Woodland-Central Colusa County Incl. I-5-Central Glenn Co &
Interstate 5-Central Motherlode 1000-3000 ft-E. Diablo Range
Above 1000 ft-E. Shasta /S. Cascades Above 3000 ft-Eastern
Colusa County-Eastern Glenn County-Glenn/Colusa Coast Range
Above 3000 ft-Lassen Volcanic NP-N. Motherlode 1000-3000 ft-N.
Sac Valley in Tehama County-NE San Joaquin Valley Below 1000 ft-
Sac Metro/W. El Dorado/Amador County-San Joaquin County Delta-
Shasta County Foothills 1000-3000 ft-Shasta Lake Area & 1-5 1000-
3000 ft-Shasta Metro-Sierra (Cal-Tuo) 3000-5000 ft-Sierra
(Sierra-Placer) Above 5000 ft-Sierra (Tehama-Plumas) 1000-3000
ft-Sierra (Tehama-Plumas) Above 3000 ft-Sierra (Yuba-Placer)
3000-5000 ft-Sierra 3000-5000 ft-Southern Motherlode 1000-3000
ft-Sutter/Yuba counties below 1000 ft-Tehama Co Coast Range
Above 3000 ft-Tracy Triangle Below 1000 ft-W Tehama Co Foothills
1000-3000 ft-W. Glenn/Colusa Foothills 1000-3000 ft-W. Shasta
County 1000-3000 ft-W. Shasta County Above 3000 ft-W. Stanislaus
County Above 1000 ft & I-5-W. Yolo County including Capay/I-505-
Yolo / Solano County Hills.

&&

$$