446
FXUS66 KSTO 171906
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
1206 PM PDT Sat Oct 17 2026
For additional details on weather and expected impacts over the
next 7 days, please visit weather.gov/sto/briefing.
.KEY MESSAGES...
- Elevated Fire Weather Conditions continue in the Sierra and
adjacent foothills, portions of the Sacramento Valley through
this evening.
- Gradual cool down begins Sunday with renewed precipitation
chances by the middle of next week.
- Onshore flow returns Sunday evening, providing temperature
relief and improved overnight/daytime humidity values Monday
through next week.
&&
.DISCUSSION...
...Rest of Today - Sunday...
Mostly clear skies once again across interior NorCal this morning.
High temperatures beginning to climb into the lower 70s across the
Valley floor, with continued warming into the upper 80s/low 90s
expected. Upper level pattern reveals high pressure moving further
north and east out of our area, with a closed low off SoCal`s
coast being the primary driver of our sensible weather. Pattern
will allow for very dry conditions to persist in the mountains and
foothills today, along with west winds however much weaker
compared to the last few days. With fuels/ERCs still very
dry/high, elevated fire weather conditions will persist through
the mountains and adjacent foothills today. SoCal low will weaken
Sunday, while a PacNW trough begins to dig south ushering in the
return of onshore flow to the region by Sunday evening. Highs will
still be in the 80s in the Valley with slightly improved
humidities throughout the day. Overnight humidity recoveries will
improve significantly as well, helping mitigate some of the fire
weather concerns in the Valley and higher elevations.
...Monday-Tuesday...
By Monday, closed low has developed and will continue to dig south
off the coast. Monday and Tuesday we will see our high
temperatures fall significantly into the upper 60s to low 70s in
the Valley with enhanced onshore flow. Wind gusts up to around 35
mph in the Delta, upslope gusts up to 40 in the mountains along
the peaks and ridges. Ensembles continue to show the low pressure
further west off the coastline, which may inhibit some of the
precipitation chances early next week. Nonetheless, NBM keeps
slight chances of Valley showers in the forecast late Monday night
into Tuesday, but confidence is very low on any activity at this
time. Better precipitation and isolated rumbles of thunder arrive
on Wednesday.
...Wednesday - Late Next Week...
Low pressure still meanders off the coast, but subtle eastward
movement on Wednesday may increase the precipitation chances
across the area Wednesday and Thursday. Latest NBM run has removed
most of the QPF totals from the Valley, with most less than 0.10"
total rain south of Sacramento. Higher rain totals still forecast
in the foothills and mountains Wed-Thu, along with best chances of
t-storms on Wednesday as a shortwave trough ejects from parent low
and moves inland. Trends continue to push precipitation chances
further along in the week, so confidence remains low on activity
developing. Snow levels look to remain above 8000 feet, and NBM
runs reduced snow totals to below 4 inches, south of HWY-50 Tue-
Thu. High confidence in pattern change, more fall like
temperatures, onshore winds returning; with low confidence on
precipitation chances and totals next week.
&&
.AVIATION...
VFR conditions prevail across interior NorCal next 24 hours. Light
surface winds in the Valley generally below 12 knots. Occasional
wind gusts up to 20 knots in higher elevations next 24 hours.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
