textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 107 PM PDT Tue Sep 1 2026

- Cooler weather continues through the week

- Beneficial wetting rain expected in the North Bay through Thursday

UPDATE

Issued at 517 PM PDT Tue Sep 1 2026

The 00Z sounding measured the marine layer at 5,200 ft. That's about as deep as possible before it loses it's structure. In fact cumulus clouds are surviving within the marine layer. The deep marine layer also allowed temperatures to climb higher than expected in the coastal areas. If the marine layer survives the night we will see a double inversion pattern. Meanwhile light rain is approaching the North Bay and should be there Wednesday morning.

SHORT TERM

Issued at 107 PM PDT Tue Sep 1 2026 (This evening through Wednesday night)

Mostly clear sky conditions have returned to the Central Coast with scattered low clouds across the Bay Area and North Bay. There are also high clouds associated with an approaching frontal boundary across the North Bay. As such, temperatures today will be 5-15 degrees below normal as the 850 mb temperature drops below 10C/50F for the first time since May. Additionally, there is a chance for for light rain and/or drizzle across the North Bay tonight into Wednesday morning with pre-fronatal coastal drizzle for areas to the south.

Low clouds will spread back inland overnight and into Wednesday morning with temperatures generally the 50s across much of the region and in the 40s in the higher elevations. Similar conditions are forecast for Wednesday with another disturbance moving in from the northwest Wednesday night into Thursday. This will bring increasing potential for light rain across the North Bay and portions of the Bay Area. The greatest potential to see greater than 0.25" will be in the coastal ranges of the North Bay and 0.10" in and around Santa Rosa and the Sonoma County valleys by Thursday morning. Rainfall amounts drastically drop off the further south you go.

LONG TERM

Issued at 107 PM PDT Tue Sep 1 2026 (Thursday through next Monday)

Heading into this upcoming weekend, there is the potential we see a slight warming trend high pressure over the central United States builds westward. However, troughing off of the West Coast will main cooler than average temperatures throughout the weekend.

Ensemble clusters diverge heading into next week. As such, still keeping an eye on tropical development over the eastern Pacific Ocean for any northward movement of tropical moisture. However, the latest guidance is indicating the track of TS Marie should stay well to our south, potentially bringing impacts to southern California. For more information on tropical developments visit nhc.noaa.gov.

AVIATION

(00Z TAFS) Issued at 426 PM PDT Tue Sep 1 2026

VFR is expected to prevail through the remainder of today and tonight with MVFR ceilings possible after midnight for the coastal terminals. A fairly well mixed marine layer was measured at ~5000ft by the 00z KOAK balloon and is not expected to change much through the forecast period. Gusty winds will ease after sunset.

Vicinity of SFO...VFR is expected to prevail through the remainder of today and tonight with a chance for MVFR ceilings after midnight, especially at KOAK if winds become light and variable, with clearing expected around sunrise.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...MVFR ceilings are the primary concern after midnight into the early morning hours Wednesday, with VFR expected by mid-morning with increased mixing under a ~5000ft marine layer.

MARINE

(Today through Sunday) Issued at 915 AM PDT Tue Sep 1 2026

Light northwesterly breezes will persist through the week with occasional moderate breezes. Slight to moderate wind driven seas will continue through the week with tropical cyclone activity producing long period southerly swell by the end of the week into the weekend.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...None.