textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 921 AM PST Tue Dec 30 2025

- Rain returns Wednesday, becomes widespread for New Years Eve, and additional rains expected over the weekend and into the next work week.

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

UPDATE

Issued at 921 AM PST Tue Dec 30 2025

Temperatures are gradually warming this morning, yet high clouds advecting across the region from the south may very well limit daytime heating this afternoon. This is especially so across the North Bay and East Bay where low clouds linger and may struggle to reach into the upper 40s to lower 50s. That said, visibilities have improve to above 1/4 mile (except at KSTS) and therefore have cancelled the Dense Fog Advisory for the North Bay and East Bay valleys.

RGass

SHORT TERM

Issued at 432 AM PST Tue Dec 30 2025 (Today and tonight)

Another mostly quiet night so far, with the cooler and dry airmass allowing for temperatures to fall into the mid 30s for the more interior areas. Cold Weather Advisories are in effect for these areas, and Dense Fog Advisories are also in effect for the North and East Bay valleys. The overnight forecast package had a focus on the cool overnight lows and the intrusion of fog from the Sacramento Valley. Additional adjustments were made to winds as well to better capture some of the increases in gusts during the offshore flow as well as the mid week pattern change.

Today's weather continues the trend of a cold morning followed by mostly clear conditions into the afternoon and highs peaking again in the 50s and 60s. Though, the late afternoon will show signs of the upcoming pattern change, as high clouds build from the south. These clouds will fill over the region as the large cut-off low to the southwest re-enters the jet stream and makes its way toward the California coast.

The orientation of this low relative to us will allow warmer and more moist air to work its way up from the south. This will have most areas seeing overnight temps plateauing in the 40s and prevent another round of Cold Weather Advisories. Then the first wave of rain arrives to the southern counties early Wednesday.

LONG TERM

Issued at 432 AM PST Tue Dec 30 2025 (Wednesday through Monday)

Models have been locked in on this cut-off low providing the California coast with another round of rain for a while, but timing and overall rain amounts had been harder to narrow down. The more recent updates and the inclusion of shorter-term, higher resolution models have lead to a better consensus. However, there still seems to be some struggles in model guidance on the finer details, possibly from how uncommon of a set up our next rainmaker will be.

It's interesting to watch, as it is already in motion: Our current ridging pattern and trough to the west has begun transporting a cut- off low northward from around the 30th parallel. This southerly pull of moisture wouldn't be out of place in months like August, but it's fairly rare mid-winter. What will this mean? Quite a bit of rain for SoCal, while light to moderate rain builds into the Central Coast early on the 31st and becoming CWA-wide as we welcome in the New Year.

The low will push inland through the second day of the new year as it gets folded into the building trough ahead of the next, more classic, winter rain system arriving into the end of the week. The time of arrival for the this system could still be delayed, but the current forecast shows a cold front arriving along the coast this Friday with it's parent low building in close behind into that weekend. This looks to offer higher rain rates and much stronger winds than the cut-off low, but does look to move through the area at a good pace, preventing chances for elevated rain rates from staying over one area for too long.

Model agreements splinter through the late weekend and into the next work week, but the ECMWF and GFS outputs do call for a wet January. The big differences between the two are more down to the timing and the paths these systems take, but they are both calling for the jet stream to become a conveyer belt of cold fronts and low pressures moving through the area. This won't leave a lot of time between rain systems and could lead to more of a marathon of rain chances. This will be something worth checking back in on as the forecast evolves.

AVIATION

(18Z TAFS) Issued at 930 AM PST Tue Dec 30 2025

Fog and low stratus persist in the North and East Bay valleys through 19-20Z. Otherwise, the region is generally VFR with extensive mid- to high-level clouds developing across the region through the day. Gentle to moderate offshore breezes will prevail through the day with little chance for showers through the day. Overnight, winds will relax, and the incoming high clouds will aim to disrupt radiative cooling and stratus development. Confidence in the forecast for fog at STS tonight has decreased, but opted to leave the TAF intact for now. Showers will build in from the south on Wednesday morning and spread throughout the region through the day.

Vicinity of SFO... Generally VFR with mid- to high level clouds through the TAF period, with a gentle northeast breeze through the day. Ceilings will lower Wednesday morning in advance of showers expected to arrive late in the morning through the end of the TAF period.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... Gentle to moderate southeast breezes developing through the day with mid- to high level cloud ceilings. Winds will relax overnight in advance of showers arriving in the pre- dawn hours Wednesday morning.

MARINE

(Today through Sunday) Issued at 921 AM PST Tue Dec 30 2025

Moderate to fresh east to northeast winds and moderate seas 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 into the early part of next week.

BEACHES

Issued at 925 PM PST Mon Dec 29 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.

PZ...None.