870
FXUS66 KSTO 082024
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
124 PM PDT Thu Oct 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 until 10 PM tonight for the
Sacramento Valley, Delta, northern San Joaquin Valley, and
adjacent foothills.
- Widespread Moderate HeatRisk with areas of Major HeatRisk
today for the Delta, Valley, and Foothills.
- Pattern change will bring cooler temperatures, unsettled
weather beginning this weekend into early next week
&&
.DISCUSSION...
...Today...
Mostly sunny skies across interior NorCal at the time of this
writing. Temperatures climbing into the 80s across Valley
locations, with continued heating expected to top off in the upper
90s/triple-digits. Moderate HeatRisk with areas of Major HeatRisk
remain the headline for today, as high pressure continues to keep
air stagnant across the region. The Heat Advisory will run through
10 PM tonight, then our upper level pattern will begin to
breakdown as we move closer to the weekend.
...Friday...
Upper level pattern begins to break down as a PacNW trough and
weak closed low form offshore. While high temperatures will still
be above normal Friday, the Delta Breeze and onshore flow will
return to the area later that evening, ushering in relief from the
summer-like temperatures in the evening. Wind gusts in the Delta
are forecast to reach 35 to 45 mph at times Friday night into
early Saturday morning, when the height gradient is expected to be
strongest. Similar gusts are expected across Coast Range gaps and
along the Sierra Crest Friday into Saturday.
...Saturday-Monday...
Gusty winds will continue through most of Saturday and we will see
our first day of more fall-like high temperatures across interior
NorCal. Highs are expected to be in the mid to upper 70s, low 80s
in the northern San Joaquin Valley. Synoptic pattern will see a
PacNW trough phase with a weak offshore low, and some moisture
associated with the remnants of Hurricane Rachel. Recent ensemble
runs are continuing to keep the bulk of tropical moisture south of
our warning area. Some moisture advection will nose into portions
of the Sierra Nevada, mainly on Sunday and Monday. Right now, best
chances of seeing 0.50" of rain remains above roughly 3000 feet
and south of I-80. With the path of the trough and an eventual low
pressure developing/closing off, isolated t-storms will be
possible in the higher elevations Sunday and Monday as well. While
the NBM keeps probabilities at or below 15%, location of the
aforementioned low will provide the lift, cold air/instability
aloft to produce t-storms if enough moisture advects.
Sunday into Monday will continue to see the low dig further south
into NorCal, which will create a north to south pressure gradient
in the Valley. Little to no precip expected in the Valley, but
periods of breezy to gusty north winds will develop; strongest
Sunday afternoon as the low treks across our area. Wind gusts are
forecast to be around 30 to 40 mph in the northern Sacramento
Valley along and west of the I-5 corridor and adjacent foothills.
We will keep the potential for elevated fire weather conditions
based on the north wind gusts, but daytime humidity values on
Sunday and Monday will likely help keep the Valley out of critical
conditions.
Still high level of uncertainty regarding exact impacts, but we
can say for certain cooler temperatures, gusty winds, and light
mountains showers with some rumbles of thunder are expected
within this pattern change.
...Tuesday and Beyond...
By Tuesday, closed low begins to translate eastward, with sensible
impacts of seasonable high temperatures and lingering mountain
showers, mainly south of HWY-50. Ensembles suggest offshore
ridging developing by Wednesday and Thursday, suggesting high
temperatures will climb back into the low to mid 80s by the middle
of the week.
&&
.AVIATION...
VFR conditions continue across interior NorCal next 24 hours.
Surface wind gusts below 12 knots, gusts up to 15 to 20 knots in
the higher elevations beginning 23z today through roughly 07z
Friday.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 10 PM PDT this evening 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-Shasta
County Foothills 1000-3000 ft-Shasta Metro-Sierra (Tehama-
Plumas) 1000-3000 ft-Southern Motherlode 1000-3000 ft-
Sutter/Yuba counties below 1000 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. Stanislaus County
Above 1000 ft & I-5-W. Yolo County including Capay/I-505-Yolo /
Solano County Hills.
&&
$$
