textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 226 PM PST Mon Dec 29 2025

- Cold overnight conditions for interior and valley locations again tonight.

- Rain returns Wednesday and lasts through the weekend.

- Coastal flooding from King Tides is expected Wednesday through Sunday.

SHORT TERM

Issued at 226 PM PST Mon Dec 29 2025 (This evening through Tuesday)

An upper level high is positioned across the northern part of California while a cut-off low pressure is in place off of southern California. This has allowed for offshore flow in the higher terrain which is expected to continue into Tuesday. As such, cold temperatures are expected across interior spots of the Bay Area and Central coast where overnight low temperatures are forecast to be as low as 33 degrees F, isolated colder spots are likely in the wind sheltered valleys. Thus, a Cold Weather Advisory has been issued for most locations away from the immediate coastline, bay shoreline, and the Santa Clara Valley.

Tuesday will feature increasing mid-to-high level clouds from a weather system approaching from the south as the aforementioned cut- off low advects moisture from the south northward. However, dry conditions are expected to prevail with temperatures similar to those this afternoon.

LONG TERM

Issued at 226 PM PST Mon Dec 29 2025 (Tuesday night through next Sunday)

The mid/upper level low pressure will advect enough moisture northward to spread rainfall across the Central Coast by Wednesday, but then will gradually spread northward across the Bay Area by Wednesday afternoon. Rainfall amounts will be generally light to occasionally moderate with the heaviest being across the Santa Lucia and Sierra de Salinas ranges where there is a marginal risk for excessive rainfall on Wednesday. Given the recent rain over the past week or two, this will lead to nuisance flooding for poor drainage areas and urban areas, as well as rises on flashy creeks/streams. That low pressure is forecast to shift inland over southern California with lingering rain likely into Thursday.

By Friday, an atmospheric river is forecast to move across the North Bay and then progress southward bringing additional rainfall to the region and a 10-15% chance for thunderstorms. This is when we are expecting the heaviest of rainfall, however the boundary does not appear likely to stall at any given point. At this point there is a marginal risk for excessive rainfall on Friday across the interior Bay Area and Central Coast. Rainfall amounts will be more refined as we near late week and get closer to the event. Unsettled conditions look to prevail into the weekend and potentially into early next week as the pattern aloft remains troughy.

AVIATION

(00Z TAFS) Issued at 404 PM PST Mon Dec 29 2025

10.6 mb WMC-SFO and 1.6 mb SAC-SFO offshore pressure gradients support ongoing offshore winds, dry conditions and high confidence VFR into the evening. Low clouds and tule fog /VLIFR-IFR/ are forecast to redevelop over the Central Valley and reach into the Delta late tonight and Tuesday. Patchy valley fog /VLIFR-IFR/ will also develop due to radiative cooling tonight and Tuesday morning. The 500 mb upper level ridge is forecast to move eastward to Nevada late tonight and Tuesday which will shift lower, mid and upper level winds to a southerly direction, advecting in high clouds starting Tuesday.

Vicinity of SFO...VFR. Southeast to east wind 5 to 9 knots tonight and Tuesday becoming light and variable by early Tuesday evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR. Winds mainly east to southeast 5 to 10 knots.

MARINE

(Tonight through next Saturday) Issued at 348 PM PST Mon Dec 29 2025

Moderate northerly winds and moderate seas will prevail through Wednesday. Fresh to strong southerly breezes return Thursday into Friday with gale force gusts likely. Seas build to become rough Thursday into Friday. Rain returns Wednesday and lasts through the weekend.

BEACHES

Issued at 945 AM PST Sun Dec 28 2025

Perigean spring tides (king tides) return Wednesday - Sunday. This is due to the combination of the full moon on 1/3, lunar perigee on 1/1, and perihelion on 1/3. In other words all three planetary bodies are lined up and close to each other. In addition to the high astronomical tide, the incoming low pressure system will bring strong onshore winds, generating some storm surge. The combination of these factors will bring minor coastal flooding to the low-lying areas near shorelines and tidal waterways during high tide Wednesday through Sunday. At the San Francisco tidal gauge, high tide is expected to be 1.5 ft above normal at 7:51 AM Wednesday, 1.7 ft above normal at 8:41 AM Thursday, 1.8 ft above normal at 9:34 AM Friday, 1.8 ft above normal at 10:26 AM Saturday, and 1.6 ft above normal at 11:18 AM Sunday. These predictions include 0.5 feet of storm surge that will enhance the astronomical tide and flooding threat. High tide varies up to 90 minutes earlier or later along the Pacific Coast and through the San Francisco Bay, respectively.

MTR WATCHES/WARNINGS/ADVISORIES

CA...Coastal Flood Advisory from 5 AM Wednesday to 2 PM PST Sunday for CAZ006-505-506-508-509-529-530.

Cold Weather Advisory from 1 AM to 9 AM PST Tuesday for CAZ504- 506-510-514>518.

PZ...None.