730
FXUS66 KSTO 092033
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
133 PM PDT Sun Aug 9 2026

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



.KEY MESSAGES...

 - Widespread Moderate to areas of Major HeatRisk continue through
   today.

 - Gradual cooling trend Monday onward with more seasonable
   temperatures and periods of breezy onshore winds through the
   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 this afternoon and evening.

 - Monsoonal moisture will bring increasing chances of mountain
   thunderstorms Tuesday through Saturday, peaking on Thursday.

&&

.DISCUSSION...The heat wave is expected to continue through
today, with widespread triple-digit high temperatures across the
Valley and foothills. There is a widespread Moderate HeatRisk and
areas of Major HeatRisk across interior NorCal. The heat will
impact anyone without effective cooling and/or adequate hydration.
A Heat Advisory remains in effect through 10 PM this evening for
the Valley and foothills, as well as mountain locations north of
Highway 50.

Elevated fire weather conditions continue through Monday due to
hot, dry, and breezy winds conditions in the northern Sacramento
Valley, Sierra foothills, and Burney Basin. Low relative
humidities in the single digits to teen`s percent are forecast
today for the mentioned areas. Additional elevated fire weather
concerns today for the Sierra Crest south of Highway 50 due to
10-15% isolated thunderstorm chances this afternoon and evening,
with the majority of the activity remaining east of the crest.

The upper-level ridge over the Four Corner will begin to breaks
down on Monday, while a mid- to upper- level shortwave trough
develops off the West Coast. Onshore flow is expected to
increase in response, providing a broader overnight relief and
increasing humidity values. Resulting in slightly cooler
temperatures on Monday, with more seasonable temperatures on
Tuesday.

Ensembles continue to suggest the upper-level trough settles over
the region by middle week, bringing more widespread cooling, with
near to below normal temperatures and Minor HeatRisk area wide
late in the week. Monsoonal moistures will bring increasing
chances of mountain thunderstorms Tuesday through Saturday, with
the highest chances (25-35%) Thursday. There is a 30-60% chance of
wetting rain over the Sierra Crest south of Highway 80 on
Thursday, with 15-30% chances over far northern Sierra and into
the southern Cascades. Additional, there is low chances (10%) for
thunderstorms over the Sierra foothill as well on Thursday.
Elevated fire weather is expected Tuesday through the weekend from
thunderstorm fire starts. Stay tuned for updates!


&&


.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 kts in the Delta from 00Z through 12Z
Monday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 10 PM PDT this evening 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.

&&

$$