744
FXUS66 KSTO 151927
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
1227 PM PDT Fri May 15 2026
For additional details on weather and expected impacts over the
next 7 days, please visit weather.gov/sto/briefing.
.KEY MESSAGES...
- A Red Flag Warning is in effect for the Valley and Delta below
1000 feet from 5 AM Saturday until 8 PM Monday.
- Critical fire weather concerns for the Valley & Delta, with
gusty north winds and low humidity. Strongest winds Saturday
night through Sunday along and west of the I-5 corridor.
- Above-normal temperatures continue through the forecast period
with Minor HeatRisk.
&&
.DISCUSSION...
....Today...
Weak ridging and westerly flow aloft will promote above-normal
temperatures and Minor HeatRisk across the area today. Highs are
expected to be in the upper 80s to low 90s across the Valley, with
mountain/foothill highs in the upper 70s to 60s. North winds will
be breezy in the northern/central Sacramento Valley, with gusts 15
to 25 mph, increasing closer to 30 mph by this evening. Further
south, the Delta Breeze will bring westerly winds into the
southern Sacramento Valley and northwest winds into the northern
San Joaquin Valley this afternoon, before winds shift to the
north overnight. Relative humidities will begin to trend lower
today into the weekend as north to northwest winds increase with
daytime RH values in the low teens to mid 20s in the Valley.
...Saturday through Monday...
Ensemble guidance depicts a trough digging into the Great Basin
this weekend, which will increase north to northwest winds through
the Valley through Monday. Winds will begin to pick up Friday
night in the northern/central Sacramento Valley before
strengthening Saturday night through Sunday. Daytime relative
humidities are expected to fall into the single digits to low
teens during this time period leading to critical fire weather
conditions. As a result, a Red Flag Warning has been issued for
the Valley & Delta from 5 AM Saturday until 8 PM Monday. Sustained
wind gusts are forecast between 20 to 30 mph with gusts 35 to 45
mph. Gusts may approach 50 mph through the Delta and far western
Sacramento Valley. Winds will begin to trend weaker on Monday,
however daytime relative humidities are still expected in the
single digits. Overnight maximum humidities will be slow to
recover Sunday night into Monday, with values in the 30s to 50s.
Over the mountains and through gaps and canyons, north to east
winds will gust 35 to 50 mph Sunday and Monday as well.
Probability of Valley Wind Gusts > 40 mph:
- Saturday`s Chances: 20-50%
- Sunday`s Chances: 65-95%
- Monday`s Chances: 10-35%
...Tuesday-Thursday...
Heights begin to rise as the trough exits the Great Basin which
will lead to gradually warming temperatures through midweek. Minor
HeatRisk will continue to be widespread, with Valley high
temperatures pushing into the mid to upper 90s. Daytime minimum
RHs will remain in the low teens to low 20s below 1000 ft
(potentially into the single digits), additionally daytime values
in the mountains and foothills will be in the 20 to 30s as well.
The continued low RHs combined with the warmer temperatures may
bring elevated fire weather conditions to the Valley next week.
Please continue to practice fire safety and monitor your latest
forecast to stay up to date at weather.gov/sacramento
&&
.AVIATION...
VFR conditions are expected over the next 24 hours. North-
northwest 8 to 15 kts and gusts 20-25 kts through Saturday 18z
with increasing winds over the northern & central Sacramento
Valley after 00z Saturday with gusts 20-35 kts. West winds over
the Sierra until 03z Friday, weakening and turning to the east
overnight.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 5 AM Saturday to 8 PM PDT Monday 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-Eastern Colusa
County-Eastern Glenn County-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 Metro-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.
&&
$$
