textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1225 PM PST Tue Jan 20 2026

- Late night and morning fog across the North and East Bay

- Light rain across the Santa Lucia Range Late Wednesday into Thursday

- Mild and mostly rain-free for the Bay Area and Central Coast

UPDATE

Issued at 606 PM PST Tue Jan 20 2026

Overcast skies will continue through the day Wednesday, keeping temperatures mild. There's a slight chance for drizzle or very light rain through the day as the cut-off low approaches the coast. Most of the precipitation will evaporate before it reaches the ground, but don't be surprised to see a few drops here and there before the low moves south and the clouds start to break up Thursday.

SHORT TERM

Issued at 1225 PM PST Tue Jan 20 2026 (This evening through Wednesday)

Fog continues to gradually dissipate across the region as mid/upper level moisture continues to lift northward. While the cloud shield is expansive, examination of our morning sounding and aircraft sounding data from SFO reveals that the low levels remain quite parched. What this translates to is high confidence that widespread rainfall is unlikely over the short term.

The primary hazard in the short term will be the re-development of fog, largely across the North and East Bay. While mid-level ridging remains in place across the area, surface flow will gradually become more southerly which may support more in the way of onshore flow. At a minimum, this should promote fog development in the favored spots of the North and East Bay, if not give us a higher chance. In fact some of the higher resolution model guidance advertises a repeat of fog across the US HWY 101 corridor across Sonoma County, similar to today.

LONG TERM

Issued at 1225 PM PST Tue Jan 20 2026 (Wednesday night through next Monday)

While general mid/upper level ridging will equate to a largely "quiet" long term forecast period, there will be some brief shifts in the main upper pattern (in addition to morning fog). These shifts will offer slight changes in the day to day sensible weather elements. Late Wednesday into Thursday, model guidance is a bit more honed in on the exact track of an upper low forecast to intensify and move eastward through Southern California. This will induce upslope flow across the higher terrain of the Central Coast. While moistening will transpire, it doesn't appear that the column will completely saturate for a prolonged period of time. In addition, the speed of this upper trough will mean a low residence time across our area. At this time, there doesn't appear to be a significant amount of spread in the track of this feature so confidence is high that overall rain amounts will remain on the light side through Thursday night. In fact, some of the higher end scenarios (90th percentile) paint up to a tenth of an inch of rainfall for this event.

By Friday evening/Saturday morning the main upper low will kick eastward. In the wake of this system, a more defined push of offshore winds is anticipated. At this juncture, the potential for winds above 35 mph is under 10%, though it may be a little higher across some of the favored gaps and passes. The story will be a little different across the marine zones as the surface pressure gradient does tighten. In fact 925mb flow does ramp up here to around 35 knots (40 mph) across Pacific waters west of Marin/Sonoma counties.

Beyond day 7, model guidance remains largely consistent with broad ridging remaining in place. At times, however, storm systems may attempt to dampen out the amplitude of the ridge and place our region within a more zonal pattern. Some of the ensemble guidance systems remain aggressive with rainfall above 1/2." While the upper air pattern depiction is largely similar from ensemble suite to ensemble suite, the spread among individual systems (e.g., EPS) remains rather high as the spread ranges from no rain to three inches of rain in some locales. As always, we'll continue to monitor, message, and adjust as necessary.

AVIATION

(06Z TAFS) Issued at 900 PM PST Tue Jan 20 2026

High overcast skies will persist through the TAF period with some patchy fog developing at the North Bay terminals through the early morning hours. There is a slight chance for very light precipitation through the day Wednesday, but not enough to impact the visibility. Winds will remain light through the night with a gentle onshore breeze developing Wednesday afternoon.

Vicinity of SFO...VMC expected to persist through the TAF period with a light easterly breeze. There is a very slight chance for mist to develop around sunrise, but the confidence is far to low to include anything more than a 6SM BR hint in the TAF.

SFO Bridge Approach...A high overcast layer will gradually lower through the day, but should remain above 8,000 feet through the TAF period.

Monterey Bay Terminals...VMC expected to persist through the TAF period with gentle winds and gradually lowering high clouds. These terminals have the best chance for light rain Wednesday, but there shouldn't be any impact to visibility either way.

MARINE

(Tonight through next Monday) Issued at 900 PM PST Tue Jan 20 2026

A gentle to moderate northerly breeze and moderate seas will continue through Thursday. On Friday winds will increase to a fresh northerly breeze, building rough seas. Conditions will improve over the weekend as a light to gentle breeze settles in and seas gradually subside to slight Sunday - Monday.

MTR WATCHES/WARNINGS/ADVISORIES

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