697
FXUS66 KSTO 051841
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
1141 AM PDT Mon Oct 5 2026
For additional details on weather and expected impacts over the
next 7 days, please visit weather.gov/sto/briefing.
.KEY MESSAGES...
- Heat Advisory now in effect till 10 PM Friday for the
Sacramento Valley, Delta, northern San Joaquin Valley, and
adjacent foothills.
- Widespread Moderate HeatRisk with areas of Major HeatRisk
through Friday for the Delta, Valley, and Foothills.
- Confidence is increasing for a cooling trend over the
weekend, with some potential for unsettled weather.
&&
.DISCUSSION...
...Today through Friday...
While some mid to high level clouds are lingering this afternoon
following last night`s foothills and mountain thunderstorm
activity, mostly clear skies currently prevail across much of
interior NorCal on GOES West satellite imagery. Slight chances
remain for further isolated thunderstorm activity in the Sierra
this afternoon, but chances decrease as we head into the evening,
and activity that does occur is primarily expected along and east
of the Sierra crest.
Despite the brief dip in temperatures yesterday, highs in the
Valley return to the upper 90s and low 100s today. These
unseasonably hot temperatures will continue through Friday in the
Valley, foothills, and Delta, along with widespread Moderate
HeatRisk and areas of Major HeatRisk. Overnight lows will remain
warm as well, in the mid 60s to mid 70s, with warmest lows in the
foothills. This means there will be limited overnight relief from
the daytime heat through the end of the week. Winds will
primarily be light and variable, helping maintain these warm
conditions. As such, a Heat Advisory remains in effect through 10
pm on Friday for the Valley, foothills, and Delta. Try to limit
outdoor activities, check on neighbors, family, friends, and
animals, and stay hydrated.
...Saturday and Sunday...
A more noticeable cooling trend begins over the weekend as a
trough potentially moves through the west coast, though there is
a significant amount of uncertainty with how significant the
cooling and troughing will be. The spread of possible
temperatures between the 25th and 75th percentiles of the NBM is
around 15 degrees, meaning highs over the weekend could be cooler
but still well above normal, or they could cool all the way to
near normal. Ensemble guidance also shows a wide spread of
possible upper level patterns, with some solutions showing deep
troughing over California, and others showing continued high
pressure (though with less pronounced ridging than what we are
currently experiencing). Solutions that do show troughing also
indicate a trough progression that will bring breezy to gusty
north to east winds starting late Saturday and continuing through
Sunday. As model guidance comes into better agreement in the
coming days, we will have a better idea of impacts, including any
potential for gusty winds, significant cooling, and even possible
precipitation.
&&
.AVIATION...
VFR conditions through the TAF period, with light northerly winds
everywhere in the Valley, less than 12kts. Some gusts up to 20
kts in portions of the foothills and mountains through 15z
Tuesday, particularly in southwest oriented canyons.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 10 PM PDT Friday 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.
&&
$$
