textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1256 PM PST Tue Dec 9 2025

- Tule fog and stratus return tonight for Bay Area valleys.

- Quiet weather continues, with high temperatures increasing through Friday.

- Light rain remains possible early next week.

SHORT TERM

Issued at 1256 PM PST Tue Dec 9 2025 (This evening through Wednesday)

Another day of watching the stratus slowly erode across the Bay area. The North Bay Valleys seem to be on track to erode by mid to late afternoon, which should keep high temperatures fairly chilly up there. It's been fun, yet challenging and humbling experience to try and nail the stratus erosion timing and high temperature forecast. This will continue to be the trend into Wednesday, though hopefully we get a little more compression from the high pressure system and perhaps slightly stronger offshore flow. If that happens, we could see warmer temperatures than forecast; however, I trended with a slightly more pessimistic forecast for Wednesday. If your'e outside the East and North Bay areas, warmer weather is on tap for Wednesday.

The area area to watch will be interior Central Coast temperatures tonight. Ended up tweaking the values in these area based on the past few nights being a touch colder than expected.

LONG TERM

Issued at 1256 PM PST Tue Dec 9 2025 (Wednesday night through next Monday)

Heights will build into for the later portion of the work week, leading to high temperatures climbing a few degrees each day. The question will be, what does that mean for our friends who have been stuck with stratus? The ridge should limit the spread of the stratus and fog, due to the marine layer compressing. If any clouds and fog do form, they should at least erode faster leading to smaller warming trend for these areas. High temperatures falter a few degrees as we head towards the weekend as upper level ridging slides eastwards. The next chance for rain may occur early next week. The dates of when this occurs seem to continue to be pushed back, so stay tuned.

AVIATION

(00Z TAFS) Issued at 602 PST Tue Dec 9 2025

Additional warming occurred today in the lower levels of the atmosphere per recent Oakland upper air sounding data and Bodega Bay profiler data. This strengthened the lower level temperature inversion today, however the difference between ground level and the base of the temperature inversion did not change much at both of these locations, at least not yet. The SAC-SFO pressure gradient is 1.7 mb and the WMC-SFO 0.9 mb. The WMC-SFO gradient is forecast to strengthen tonight and Wednesday, both gradients support ongoing offshore winds tonight and Wednesday.

The synoptic pattern remains favorable for plentiful tule fog and low stratus to continue over the Central Valley, corresponding to ongoing chilly temperatures and higher surface pressures in the valley. There'll be very little if any interference in outgoing radiative cooling tonight; it's dry above the lower level temperature inversion and cirrus clouds will be at a minimum tonight. Expect redevelopment of fog and stratus /LIFR-IFR/ in our area including the potential for dense tule fog /VLIFR/ to be transported into the Bay Area on light offshore winds tonight and Wednesday. Key to mix out times, if they are earlier tomorrow than recently observed, will be the base of the lower level temperature inversion, if it does not move downward much then it's a persistence forecast with late day break out times if at all. In areas where VFR has prevailed recently the probability of VFR or mixing out from late night and morning fog and stratus /VFLIFR-IFR/ is greater for Wednesday. This is a very challenging forecast, forecast confidence regarding mix out times Wednesday is low.

Vicinity of SFO...Low confidence VFR forecast tonight, with ongoing light offshore surface winds these winds may transport stratus ceilings and fog to SFO tonight and Wednesday morning. The difference between the air temperature and dew point temperature is small, radiative cooling and advection may work together to bring the atmosphere back to saturation i.e. stratus and fog development. Offshore winds continue for the 00z TAF.

SFO Bridge Approach...Slant range visibility may be moderate to poor at sunrise and sunset due to trapped hazy conditions. Light offshore winds may also bring low stratus and fog to the SFO approach, bringing a cloud ceiling and reducing the visibility anyhow. It's a low confidence VFR forecast for SFO and the SFO approach.

Monterey Bay Terminals...The highest probability of VFR is here, though radiative cooling may result in patchy fog to patchy dense fog /LIFR-VLIFR/ in the Salinas Valley tonight and Wednesday morning. Cold air drainage winds will result in southeasterly winds tonight and Wednesday, possibly shifting to light and variable temporarily Wednesday afternoon.

MARINE

(Tonight through next Monday) Issued at 408 PM PST Tue Dec 9 2025

Northerly flow remains over the waters with high pressure off the coast. Winds are locally stronger south of Point Pinos leading to hazardous conditions today. Winds will strengthen across all outer waters by midweek. A new, long period northwesterly swell is expected by midday Wednesday, lasting into the early weekend.

BEACHES

Issued at 132 AM PST Tue Dec 9 2025

Long period swell will impact the coast Wednesday - Friday. This energy brings strong rip currents, an increased risk for sneaker waves, and large breaking waves. NW swell around 8 feet with a 15 second period will translate to breaking waves up to 15-20 feet. These conditions may warrant a Beach Hazards Statement, particularly with the warm weather likely luring more people to the Beach.

MTR WATCHES/WARNINGS/ADVISORIES

CA...Beach Hazards Statement from Wednesday morning through Friday evening for CAZ006-505-509-529-530.

PZ...Small Craft Advisory until 9 AM PST Wednesday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

Small Craft Advisory until 3 AM PST Thursday for Pt Arena to Pt Reyes 10-60 NM.

Small Craft Advisory until 3 PM PST Wednesday for Pigeon Pt to Pt Pinos 10-60 NM.