textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1122 AM PDT Fri Sep 4 2026

- Hazardous conditions at Pacific Coast beaches Friday through Monday

- Below normal temperatures through the weekend, gradual warming and drying trend kicks off Monday

- Remnant tropical moisture likely Tuesday through Thursday

SHORT TERM

Issued at 1258 AM PDT Sat Sep 5 2026 (Today and tonight)

On Thursday the presence of mid to upper level troughing and a surface cool front brought many (but not all locations) an early rain, in some cases an early September daily record breaking rain. Atypical cool air aloft for early September carried over to Friday and plenty of cool air aloft is still lingering at this hour early Saturday morning. With current temperatures broadly in the 50s/60s, coolest at higher elevations, it's relief e.g. for a time of year here when it can easily be much warmer at higher elevations in the lower level temperature inversion under high pressure aloft. Mountain top air temperatures from Mt St Helena all the way to Chews Ridge are currently in the lower 50s. Mt Hamilton 30 year early Sep normal low for example is 62F.

Recently sea surface temperatures in our coastal waters have bumped upwards to the lower to mid 60s north to south, now 2F to 5F above Sep normals. This is resulting in a warming effect on nearby coastal locations where daily minimums are remaining a few to several degrees warmer than normal. The usual night/morning chill may be noticeably absent in the last few days.

If you're enjoying the daytime temperatures from the coast to far inland, daytime highs today will be similar to maybe a few degrees warmer with 60s/70s coastside/bayside to the upper 70s to lower 80s inland.

LONG TERM

Issued at 1258 AM PDT Sat Sep 5 2026 (Sunday through next Friday)

Forecast daytime highs Sunday will be similar to Saturday's highs, 60s/70s coastside/bayside to the upper 70s to lower 80s inland. Dry weather will continue Sunday. A weakening or break in mid to upper level troughing will begin on Labor Day with thermal ridging developing aloft resulting in a warming trend across the forecast area. This will result in daytime highs warming back to and slightly above normal e.g. 80s to lower 90s inland to far inland locations.

Global models are still showing redevelopment of 500 mb troughing over the eastern Pacific during the middle of next week. 00z guidance however is showing some retrogression of the upper level trough. This will be at the same time remnant tropical moisture moves northward and may get entrained into the trough. Our official forecast shows light rain next week, and it still bears monitoring however the precipitation forecast over our area has trended drier.

AVIATION

(06Z TAFS) Issued at 1010 PM PDT Fri Sep 4 2026

Little change to the forecast this evening as VFR conditions prevail for the time being. Satellite shows some patchy stratus and/or fog developing around Marin County and San Mateo County, with mainly clear skies elsewhere. The forecast remains a bit tricky for later tonight and into Saturday morning. The highest confidence for stratus and patchy fog development remains across the North Bay terminals, where lingering moisture from the rain would promote radiation fog/stratus. Around the Bay Area, some guidance tries to show it develop around KOAK and KSFO while other inland terminals remain VFR. Any low cloud and fog that develops should be short lived, mixing out a few hours after sunrise. VFR conditions are expected to prevail after that. Medium to high confidence in the forecast.

Vicinity of SFO...Clear skies are being observed around most of KSFO this evening, with a few clouds just now popping up around the San Bruno area. The question remains, does KSFO gets stratus tonight? Some hi-res guidance, such as the HRRR and the HREF, now show a 40- 60% chance of development on the west and north side of the San Mateo Peninsula/San Bruno Gap. Opted to keep SCT MVFR cigs in the TAF tonight as a result, with low clouds eroding by mid to late morning. Some mid level clouds may return for the afternoon and evening, which will be accompanied with another round of breezy onshore winds. Medium to high confidence in the stratus forecast, high confidence in the wind forecast.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...The toughest forecast might be around the Monterey Bay tonight, though the question is will the marine layer return? Do we get radiational cooling to promote some stratus development. Confidence is low to medium for the terminals in this area, as hi-res models keep us VFR all night, while MOS, GFSLAMP, and the NBM want to sock us in with stratus. Opted to start lifting/improving the cigs given hi-res guidance has backed off on srrtatus development.

MARINE

(Tonight through next Thursday) Issued at 1010 PM PDT Fri Sep 4 2026

West to northwest breezes will be gentle to moderate through the beginning of next week. There will be occasionally moderate to strong breezes across the San Pablo, San Francisco and Monterey Bays by the end of the weekend into the beginning of next week. Long period southerly swell has arrived with the Point Sur Buoy registering 18 second period early this afternoon out of the SSW. The long period southerly swell will continue through the weekend into the beginning of next week.

BEACHES

Issued at 1010 PM PDT Wed Sep 2 2026

A Beach Hazards Statement is in effect Friday-Monday as the swell from both Hurricane Marie and Hurricane Karina reaches the coast. As these hurricane whip up the ocean, the waves travel over 1,000 miles in all directions, gradually flattening out to low amplitude, but long period swell. These waves aren't very intimidating if you're on a boat in the open ocean, but the long period allows them to push much farther up the beach. Long period swell always increases the chance for sneaker waves, but that's particularly true this weekend since there are 2 different sets of southerly swell, and their energy will periodically combine. In addition to sneaker waves, expect strong rip currents and breaking waves up to 10 ft. As this is a holiday weekend and the weather is otherwise pretty nice, the exposure to the risk is high. Avoid the water if you're not an expert swimmer. If caught in a rip current, swim parallel to shore until you stop feeling the pull. Even on the beach, be prepared for sneaker waves this weekend and never turn your back on the ocean.

MTR WATCHES/WARNINGS/ADVISORIES

CA...Beach Hazards Statement through Monday evening for CAZ006-505- 509-529-530.

PZ...Small Craft Advisory from 9 AM to 9 PM PDT Sunday for Mry Bay.

Small Craft Advisory from 9 AM Sunday to 3 AM PDT Monday for Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.