textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1211 AM PDT Thu Sep 17 2026

- Cooler temperatures through Thursday

- Warming trend Friday into the weekend

SHORT TERM

Issued at 1211 AM PDT Thu Sep 17 2026 (Today and tonight)

Satellite imagery once again shows stratus hugging portions of the coast and beginning to move inland. As noted in the evening update, this isn't a classic marine layer. It has a more strato-cu vibe due to the proximity of cold upper level low near Pt Arena. Do expect stratus to eventually fill in along a majority of the coast by sunrise. The lower heights aloft have also allowed the cloud deck to deepen 2500-3000 ft per profilers and ACARs sounding. Given the nearby low,onshore flow, and deep layer drizzle remains in the forecast as well.

Outside of drizzle chances - similar to yesterday the main weather highlights for today will be below normal temperatures and gusty onshore flow. Generally speaking - max temps today will be a few warmer than yesterday, but still below seasonal averages. Highs will top out in the 60s to near 70 along the coast and 70s to mid 80s interior. Onshore gradients aren't overly impressive overnight, but still seeing some gusts 30-45 mph for the Delta and E Bay Hills. These gusty conditions will lingering through the early morning hours before easing through the afternoon/evening hours.

Thursday night: the upper low begins to lose its grip on the Bay Area as it slowly moves to the northeast. Behind the departing low shortwave ridging builds. A more classic marine layer will develop with solid stratus along the coast and inland valleys. Cannot rule out some patchy drizzle.

LONG TERM

Issued at 107 AM PDT Thu Sep 17 2026 (Friday through Wednesday)

Friday will be a transition day as the upper low fully exits to the northeast and shortwave ridging builds overhead. Once the morning marine layer rolls back to the coast a marked warming trend will develop to kick off the weekend. 5-10 degrees of warming are expected. The warming trend will continue through Saturday with temperatures reaching above normal by Saturday. A few low 90s will return Saturday afternoon across the interior Central Coast. Temperatures will also get a boost on Saturday with a few bursts of offshore flow. Nothing overly strong, but a switch nonetheless. Offshore winds will be most realized over the higher terrain of the N and E Bay. The warm up will be short-lived as the ridge gets replaced by yet another upper low moving in from the west on Sunday. Marine layer will likely deepen and temperatures cool 5-10 degrees.

Monday and beyond is still on the lower end of confidence. Tonight's 00Z model suite is starting to show a roller coaster of temps next week. A slight warming up and then a slight cool down. Uncertainty on the shoulder seasons is actually pretty common. Cluster analysis doesn't provide a lot of additional clarity except that models are split. Not expecting rain per se the uncertainty is around temperatures.

AVIATION

(12Z TAFS) Issued at 421 AM PDT Thu Sep 17 2026

A patchwork of VFR to IFR conditions prevails over the region with stratocumulus persisting over the Bay Area and parts of the Central Coast through the pre-dawn hours. The cloud deck should retreat back to the coastal regions through the late morning and afternoon hours, with a gentle to moderate onshore breeze developing in the afternoon. This evening and overnight, the marine layer will begin to compress, which should result in lower ceilings although confidence in ceiling heights and timing is moderate at best.

Vicinity of SFO... Low-end VFR to high-end MVFR clouds continue through the late morning hours, with a moderate west breeze developing in the afternoon. The clouds should return in the evening to overnight hours, with moderate confidence in timing and ceilings height.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... The southern Monterey Bay region has generally remained clearer than areas to the north but the latest satellite imagery shows the cloud deck moving into the region with MVFR ceilings expected to develop imminently. Clouds will retreat back to the immediate coast through the late morning hours with a gentle west-northwest wind developing in the afternoon. Winds will become light overnight with indications that MVFR clouds will return, although confidence in timing is moderate.

MARINE

(Today through Tuesday) Issued at 421 AM PDT Thu Sep 17 2026

Gentle to moderate breezes continue across the waters through Friday, when hazardous conditions for small craft return and persist into the weekend due to fresh to strong northwesterly breezes. Slight to moderate seas will prevail through Sunday.

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 to 9 PM PDT Friday for Pt Pinos to Pt Piedras Blancas 0-10 nm.