textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 401 AM PST Fri Jan 23 2026

- Morning fog across some Bay Area Valleys and around Monterey

- Gusty offshore winds across higher terrain of the North Bay Saturday

- Potential weak storm system in the middle of the next work week

UPDATE

Issued at 841 AM PST Fri Jan 23 2026

A deeper marine layer around 1500 feet in depth has returned to the region while resulting in widespread low clouds. Meanwhile, tule fog is spreading westward resulting in dense fog across the East Bay Valleys. These conditions are forecast to improve with clouds lifting and eventually clearing out by mid-to-late afternoon, last to be across the Central Coast. Offshore winds will increase late tonight and continue into Saturday in the higher terrain over the North Bay and East Bay. The ongoing forecast remains on track with no updates anticipated at this time.

RGass

SHORT TERM

Issued at 401 AM PST Fri Jan 23 2026 (Today and tonight)

Reducing pressure has brought a stronger return of the marine layer tonight. This along with a reduction of high clouds, some moisture from the Central Valley, and a slight feed of moisture from the south has allowed for a good spread of stratus and developing pockets of fog. Temperatures have slowed their cooling and are almost plateauing for the areas affected by the marine layer.

High-resolution short term models show that these clouds and pockets of fog will be slow to erode. The next developing ridge will begin to push weak northerly flow into the North Bay by the the late morning. The slightly drier air will help to clear the North Bay, while cloud cover farther to the south lingers into the afternoon. High temperatures will be slightly cooler than previous days because of the prolonged cloud cover, but only by a few degrees.

The approaching ridge will compress the marine layer and reduce the additional feeds of moisture tonight, leading less low cloud cover and fog across the area. However the more fog-proned valleys (Sonoma Co, Salinas Valley ect) will still have good chances for fog returning tonight.

LONG TERM

Issued at 401 AM PST Fri Jan 23 2026 (Saturday through Thursday)

The eastern portion of the developing ridge will continue to build into the region into early Saturday, calling for stronger northerly to northeasterly (offshore) flow. The change in winds will lead to widespread drying into Saturday, and a mixing out of the marine layer. Morning clouds and fog will be much quicker to erode across the region and that earlier clearing along with the generally drier airflow will cause slightly warmer temps for Saturday.

Higher elevations look to see breezier and gustier winds as the offshore flow increases into Saturday morning and through the day. Extra adjustments were added to the overnight forecast package to better capture the flow and speed changes, especially in the higher peaks of the North Bay. Localized gusts around 50 mph will be possible on some of the peaks, but luckily it won't be widespread. Humidities in these elevations will suffer from these increased and drier winds, leading to some fire weather concerns with a few areas falling below 20% humidity. Winds look to reduce into that night, but humidities will struggle to recover on the higher peaks. Low cloud cover and fog will struggle to form Sunday morning because of the dry flow, but high clouds enter the area into that afternoon, leading to cooler high temps.

The ridge looks to flatten into Sunday evening, with a zonal jetstream pattern taking its place, and offering more onshore flow. However the jetstream looks to snap back to a quick ridge into the next work week. This means temperatures will and some bounces up and down by a few degrees, and low cloud formation will be spotty.

Despite the quick ridge development, high clouds look to move through the region as a trough develops to the west. The trough formation is well-argeed upon between the longer term models, but the trajectory is a matter of debate. More models point to a cold front, and maybe a weak low pushing through the area, bringing good chances for widespread moderate rains by the mid week. However, the GFS and its ensemble members seem keen on this trough getting pushed up against the ridge ahead of it, and placing all the moisture well to the north. The GFS output looks a bit less firm than other models and the national blend, but is something to keep in mind as the longer term models update. For now, the official forecast places rain chances in the middle of the next work week along the initial front with additional chances possible beyond the forecast period.

AVIATION

(18Z TAFS) Issued at 956 AM PST Fri Jan 23 2026

Satellite imagery shows almost all of the Bay Area and Central Coast socked in with fog and stratus, unless your over 3000 or 4000ft elevation. The question for today becomes, will we be able to mix out? Model guidance has not been the greatest with many showing clearing happening around 18Z. MOS guidance might be the most pessimistic, with some sites potentially being locked in through the day. Opted to trend more pessimistic given the spread of this and the lack of clearing. Should this tule fog and stratus stick around, expect MVFR to IFR cigs at the terminals through the period. If we're able to mix out and get winds a little breezier, we may get some VFR conditions for a few hours.

Tonight, the forecast is difficult once again. Opted to go pessimistic for most TAF sites as well given models have struggled this morning. Look for another night of MVFR to LIFR conditions.

Vicinity of SFO...Moderate to low confidence in the SFO forecast. Opted to trend with cigs clearing later this afternoon and then staying VFR through the period. Given most guidance has low clouds flirting around SFO, opted to keep the mention of FEW015 and SCT010 in the forecast. Some guidance shows 20-40% chance of BKN MVFR cigs overnight, with cigs eroding shortly after sunrise. Will need to keep an eye on the overall forecast given the current cloud deck over the region.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...MVFR to IFR cigs are being observed this morning and these should remain locked in through the period. We should see a brief period of onshore winds this afternoon, otherwise winds look to be light and variable.

MARINE

(Today through Wednesday) Issued at 841 AM PST Fri Jan 23 2026

Fresh to strong northerly breezes will prevail today with near gale force gusts in the northwest waters. Elsewhere, gentle to fresh northerly winds prevail. Seas will build to 8-12 feet across exposed waters today through early Saturday. Conditions will improve this weekend with a gentle breeze and moderate seas.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory until 3 AM PST Saturday for Pt Arena to Pt Reyes 10-60 NM.