103
FXUS66 KSTO 071933
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1233 PM PDT Fri Aug 7 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 and low humidities.

 - Isolated thunderstorm (10%) chances along the Sierra Crest
   south of Highway 50 through the weekend.

&&

.DISCUSSION...
Upper level ridging and rising heights aloft will continue to
dominate the weather pattern for interior NorCal today and into
the weekend. The ridge axis is currently centered over the Great
Basin today, and while it is expected to gradually shift eastward
toward the Desert Southwest over the weekend, high heights aloft
will continue to provide above normal temperatures even into early
next week. Hottest temperatures are still anticipated through
Sunday, with widespread triple digit high temperatures across the
Valley and foothills and overnight low temperatures in the mid 60s
to 70s. Current probabilities for high temperatures greater than
105F sit around 60-90% in the northern Sacramento Valley, with
10-20% probabilities elsewhere. Additionally, probabilities of
overnight low temperatures greater than 80F sit around 20-40% for
foothills thermal belts along the Sierra and into portions of the
northern Sacramento Valley. With resultant widespread Moderate
HeatRisk and areas of Major HeatRisk forecast, 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 broadly expected to persist across
the region, a plume of monsoonal moisture will introduce a slight
(10%) 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.

Moving into early next week, a building trough aloft is expected
to usher in a pattern change to the region, but the current
expectation is that the transition will be gradual as the ridge
slowly breaks down through the middle of the week. Temperatures do
look to respond to this transition with near to slightly above
normal temperatures returning across the early week period and
incrementally increasing onshore flow providing broader overnight
relief and increasing humidity values. There is still some noted
uncertainty on the timing and location of the deepening trough
after the middle of the week, but current ensemble trends indicate
potential for 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 25 kts in the Delta from 00Z through 12Z
Saturday.

&&

.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.

&&

$$