467
FXUS66 KSTO 151907
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
1207 PM PDT Thu Oct 15 2026
For additional details on weather and expected impacts over the
next 7 days, please visit weather.gov/sto/briefing.
.KEY MESSAGES...
- Red Flag Warning in effect until 10 AM PDT Friday for the
Sierra and adjacent foothills.
- Dry and warm weather with gusty east-northeast Sierra winds
through the end of the week.
- Gradual cool down through the weekend with renewed
precipitation chances early to mid next week.
&&
.DISCUSSION...
...Rest of Today-Friday...
Mostly clear skies observed across interior NorCal at the time of
this writing. Upper level pattern reveals a ridge of high pressure
deepening inland and weak troughing developing to the southeast of
the area. Pattern will continue to allow for gusty north to east
winds in the Sierra Nevada and adjacent foothills, north winds in
the Valley, and low humidity values. Some observation points in
the higher elevations have recorded wind gusts of 40 to 45 mph
this morning, as well as morning RH values in the teens to low
20s, creating critical fire weather conditions. As the ridge and
low deepen, winds will once again increase as we move into the
evening and overnight areas. The Red Flag Warning will continue in
the Sierra and adjacent foothills through at least 10 AM Friday.
NBM probabilities of wind gusts greater than 40 mph in the
mountains are around 70-90% this evening and overnight, as the
resultant pressure gradient will be the strongest. Overnight RH
recoveries will remain in the low 20s to 30s, similar to what we
saw this morning.
Elsewhere in the Valley, periods of breezy north to east winds
will develop; strongest along and west of the I-5 corridor today
and Friday. Locally stronger wind gusts of 30 to 40 mph in Colusa,
Yolo, and northwestern Solano Counties will develop Friday as
well. Elevated fire weather conditions will continue in the Valley
and areas listed above tomorrow when winds are the strongest and
humidity values are at their lowest. High temperatures will
continue to warm today and Friday, with highs reaching the low 90s
across much of the Valley. Ridge axis will begin to slowly move
to the east, while a weak cut-off low forms in SoCal by Friday,
keeping those dry and breezy to gusty conditions lingering through
the afternoon/evening.
...Weekend into Next Week...
By Saturday, the ridge moves further east, and cut-loff low
remains off the coast of SoCal. Pattern will allow for slight
cooling to begin across the region, but only by a few degrees
keeping temperatures above normal with continued dry conditions.
Offshore winds will ease as well as the upper air pattern
continues to evolve. Sunday, a notable pattern change will begin
as the aforementioned SoCal cut-off low will factor more into our
weather pattern, allowing onshore flow to return to the area. High
temperatures will cool to the low 80s across NorCal on Sunday and
humidity values will see much better recoveries. Low pressure
will also develop in the PacNW and begin to dig further south
Sunday afternoon/evening.
Further southerly movement of the PacNW low and associated
offshore troughing will cool temperatures further Monday through
Wednesday, as well as introduce some slight shower chances to the
region. Uncertainty remains relatively high on where the PacNW low
will track, but recent ensemble runs are trying to keep the
parent low offshore. Pattern would suggest better precipitation
chances in the mountains and foothills, and the NBM probabilities
reveal the best chances (50-70%) of 0.10" of measurable rain will
be in the higher elevations. We will continue to monitor the track
and strength of this system, but overall a cooldown and return of
onshore flow are very likely early next week.
&&
.AVIATION...
VFR conditions continue across interior NorCal next 24 hours.
Light to locally breezy north winds less than 12 knots at Valley
TAF sites. North wind gusts up to 15 to 20 knots at RDD and RBL
beginning roughly 20z today and continuing through the forecast
period Friday. East to northeast wind gusts of 30-45 knots along
the Sierra next 24 hours. Additional north wind gusts of 20-30
knots in Yolo and Colusa counties 20z today.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 10 AM PDT Friday for Central Motherlode
1000-3000 ft-N. Motherlode 1000-3000 ft-Sierra (Cal-Tuo) 3000-
5000 ft-Sierra (Cal-Tuo) Above 5000 ft-Sierra (El Dorado-Amador)
Above 5000 ft-Sierra (Sierra-Placer) Above 5000 ft-Sierra
(Tehama-Plumas) 1000-3000 ft-Sierra (Tehama-Plumas) Above 3000
ft-Sierra (Yuba-Placer) 3000-5000 ft-Sierra 3000-5000 ft-
Southern Motherlode 1000-3000 ft.
&&
$$
