textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1057 PM PDT Thu Sep 17 2026

- Warming trend Friday into the weekend

- Brief cooldown Sunday

- Notable warming trend next week

SHORT TERM

Issued at 1057 PM PDT Thu Sep 17 2026 (Today and Tonight)

Friday will be a transition day as the upper low from the last 24-36 hrs exits to the NE. During this transition we'll see some clouds again Friday morning, but not in the classic marine layer environment. More of a synoptically enhanced strato-cu set up with lingering lift from the departing low. Regardless of the reason, cloudy to start off the day with some patchy drizzle possible again. For what it's worth looking way north toward the OR coast a more marine layer stratus deck is solidifying as the subsidence inversion returns with building high pressure. I digress, the low exits today and shortwave ridging is to follow for Friday into Saturday. Shortwave ridging will kick off a brief warming and drying trend for the Bay Area and Central Coast. Max temps today will see a 5 to 15 degree jump from Thursday's readings. Not a bad way to begin the weekend with highs in the 60s and 70s coast and 70s to upper 80s inland. As high pressure builds in from the N and W and interior heats up we'll see an uptick in winds this afternoon. Strongest winds for the inland valleys and gaps/passes with gusts of 25-35 mph.

Friday will be interesting as the marine layer tries to reform with building high pressure, but a burst of offshore flow also develops over the higher terrain. Not strong by any means, but drying nonetheless. As such, think some stratus will develop along the coast and move inland. The real battle ground will be along the N Bay coast and N Bay Valleys where the offshore flow may win out.

LONG TERM

Issued at 1145 PM PDT Thu Sep 17 2026 (Saturday through next Thursday)

The warm up from Friday continues into Saturday with another few degrees or warming. Warmest inland locations will reach the low 90s. Elsewhere lots of 70s and 80s - immediate coast 60s.

The rest of the long term is a little bit of a roller coast - sensible weather changes, but thankfully not major impactful changes. The shortwave ridge quickly gets replaced by a small fast moving upper level low. The biggest change from the passing upper low will be dropping daytime temps by up to 10 degrees. Monday will be another transition day as the upper low exits initiating a subtle warm up.

For the rest of next week had been rather uncertain with a variety of model solution. A slight trend in the longwave pattern was developing last night and tonight that trend continues. A very notable upper level trough/low develops near the Gulf of Alaska. Downstream of the feature a ridiculous ridge blankets the eastern half of the CONUS with very impressive heights nosing E Canada. This large area of high pressure also oozes westward, including some of CA. As a result, a warming trend kicks in just in time for the fall equinox. The peak of heat appears to happen Wednesday and Thursday. Current forecast has far interior locations reaching the mid to upper 90s with HeatRisk values reaching moderate. Stay tuned...

AVIATION

(06Z TAFS) Issued at 1032 PM PDT Thu Sep 17 2026

A difficult forecast tonight as a well-mixed lower layer has practically eliminated any distinct marine layer and the clouds tend towards more stratocumulus than purely stratus across the region. Some MVFR ceilings have developed along the coast and within topographically favored regions. The rest of the region should generally expect MVFR to low-end VFR ceilings to come in through the night and particularly through Friday morning. The cloud deck should retreat back to the coast through the post-sunrise hours, with gentle to moderate onshore winds expected in the afternoon and evening. Friday evening, the marine layer should redevelop as subsidence returns to the region, and some stratus could return to the coastal terminals before the end of the 24-hour TAF period.

Vicinity of SFO... Transient MVFR ceilings are possible through around 11-12Z, when more persistent ceilings arrive at the terminal. The clouds should clear out around 18Z with a moderate west-northwest wind developing in the afternoon and evening hours. Stratus could return to the terminal region late Friday night into Saturday morning, but confidence in timing is low.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... Generally VFR through the next few hours with patches of MVFR ceilings possible near favored terrain. More extensive cloud coverage arrives in the early hours of Friday morning before the clouds diminish after sunrise. Gentle to moderate northwest winds will develop Friday afternoon. Friday evening, high resolution model output is showing stratus returning to the region, but confidence in development time is low.

MARINE

(Tonight through next Wednesday) Issued at 1032 PM PDT Thu Sep 17 2026

West to northwest gentle breezes become moderate to fresh by Friday afternoon into the weekend. Strong gusts up to 30 kt are possible across the northern coastal waters, Big Sur coastal jet region, and the Monterey Bay region Friday into Saturday. Winds gradually diminish across the southern coastal waters by Saturday evening, but remain elevated across the north. Slight to moderate wind driven seas persist through the weekend and steadily build to rough by early next week.

FIRE WEATHER

Issued at 421 AM PDT Thu Sep 17 2026

The coolest conditions and deepest marine layer are expected through the day today as the upper level low stalls over northern California. Current observations suggest a marine layer depth of over 3000 feet, allowing for moist conditions to reach very high into the higher elevations. As the low moves away on Friday, the marine layer will compress, temperatures will rise, and relative humidities in the higher elevations will start to decrease. Some offshore flow is possible on Saturday morning, but it is not expected to be very strong and the bulk of the offshore influence will be felt on the higher terrain of the North and East Bay.

DialH

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory from 3 PM Friday to 3 AM PDT Saturday for Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm.

Small Craft Advisory from 3 PM Friday to 3 PM PDT Saturday for Pt Arena to Pt Reyes 0-10 nm.

Small Craft Advisory from 3 PM to 9 PM PDT Friday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

Small Craft Advisory from 9 PM Friday to 3 PM PDT Saturday for Pt Arena to Pt Reyes 10-60 NM.