618
FXUS66 KSTO 081947
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1247 PM PDT Tue Sep 8 2026

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

.KEY MESSAGES...

  - Drying and warming trend through Thursday, with areas of
    Moderate to Major HeatRisk Wednesday and Thursday.

  - Heat Advisory is in effect 10 am Wednesday - 10 pm Thursday
    for the Delta, Valley, and foothills.

  - Cooling temperatures late week into the weekend.

  - Breezy onshore winds Friday-Saturday followed by gustier north
    winds Sunday-Monday.

&&

.DISCUSSION...

Today-Thursday:
A fluctuating weather pattern is setting up across the region
today with split flow aloft currently over interior NorCal. Desert
Southwest ridging is beginning to creep eastward however;
introducing rising heights aloft and the anticipated warming trend
through the middle of the week. High temperatures start to climb
into the 90s throughout the Valley today, jumping up to the upper
90s to triple digits on both Wednesday and Thursday. With
predominantly light to breezy offshore winds accompanying the
pattern, overnight low temperatures are expected to remain
relatively stagnant in the mid 60s to 70s as well. As result, a
Heat Advisory remains in effect from 10 am Wednesday through 10 pm
Thursday for the majority of the Delta, Valley, and foothills
with widespread Moderate HeatRisk and areas of Major HeatRisk in
the forecast through Thursday.

Dry weather and periodically breezy north to east winds are also
on track to accompany the warming trend over the next few days.
Wind gusts generally look to remain around 15-20 mph through
Wednesday, strongest overnight and into late Wednesday morning.
Lighter north winds are then anticipated into Thursday morning
with south to west onshore winds of a similar magnitude increasing
by Thursday afternoon. Daytime humidity values in the teens, with
some single digits possible, and poor overnight recovery
alongside these breezy winds will yield elevated fire weather
conditions across the region through Thursday.

Friday Into Early Next Week...
Ridging and high heights aloft will begin relaxing by late
Thursday as a longwave trough starts to drop down from interior
British Columbia. This is expected to lead to an abrupt cool down
to more seasonable high temperatures by Friday with a trend toward
slightly below normal temperatures through the weekend and into
early next week. Breezy onshore winds look to return as well with
this pattern shift introducing some improvements to daytime
humidity and overnight recoveries.

There continues to be increasing confidence within ensemble
guidance for the aforementioned trough to dig south through the
end of the weekend before ejecting eastward into early next week,
although some uncertainty regarding the exact trajectory remains.
Despite this, periods of breezier onshore winds are currently on
track for Saturday before shifting to gusty north to east winds
Saturday evening through Sunday. Currently, probabilities for
northerly wind gusts greater than 30 mph sit around 20-40% on
Sunday, highest along and west of the Interstate 5 corridor. While
exact details remain uncertain, some potential for elevated fire
weather concerns will be possible late weekend into early next
week.

&&

.AVIATION...

VFR conditions prevail at TAF sites across the forecast period.
Breezy north to east winds are expected at times, although
remaining 12 kts or less, with strongest winds through the Valley
and Delta in the late morning and afternoon hours, especially
after 15z Wednesday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 10 AM Wednesday to 10 PM PDT Thursday for
Butte County Below 1000 ft-C. San Joaquin County including
Stockton-C. Solano County including Fairfield-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-
Eastern Colusa County-Eastern Glenn County-N. Motherlode 1000-
3000 ft-N. Sac Valley in Tehama County-NE San Joaquin Valley
Below 1000 ft-SW Solano County including Vallejo-Sac Metro/W. El
Dorado/Amador County-Sacramento County Delta-San Joaquin County
Delta-Sierra (Tehama-Plumas) 1000-3000 ft-Southern Motherlode
1000-3000 ft-Sutter/Yuba counties below 1000 ft-Tracy Triangle
Below 1000 ft-W. Stanislaus County Above 1000 ft & I-5-W. Yolo
County including Capay/I-505-Yolo / Solano County Hills.

&&

$$