Swell Matrix

Area Forecast Discussion

National Weather Service San Francisco Bay Area

331 am PST Tue Jan 18 2022


Mostly dry and mild weather conditions will prevail through midweek with subtle warming late in the week. Breezy to gusty offshore winds are expected in the higher terrain of the North Bay, East Bay and San Francisco Peninsula on Wednesday and Thursday.


As of 03:02 AM PST Tuesday, Isolated lingering rain showers continue to be detected on KMUX Radar this morning moving southward across the Los Padres National Forest. Otherwise, most of the high-based rain showers associated with the mid/upper level low to the south have ended. That said, humid and mild temperatures persist over the Central Coast with temperatures still in the 50s early this morning in response to modest moisture advection. Low clouds have also been on the increase this morning along the coast with patchy fog developing across interior valley locations (particularly in Marin and Sonoma counties).

Dry weather conditions will return region-wide today as high pressure builds over the eastern Pacific in wake of the exiting mid/upper level feature to the south. This will result in daytime temperatures peaking in the upper 50s to mid 60s with a mix of Sun and clouds. Similar conditions are likely to persist through midweek along with minimum temperatures dropping into the upper 30s in the colder interior valleys to the 40s for most other areas. As a mid/upper level trough pushes into the Pacific Northwest and then dives southward into the Great Basin, offshore winds will develop over much of the Bay Area from Wednesday into Thursday. The strongest winds are likely to be confined to the higher terrain of the North Bay, East Bay and San Francisco Peninsula with gusts potentially in excess of 40 mph. Something worth keeping an eye on in the coming days.

Otherwise, building high pressure off of the West Coast will result in a gradual warming trend late in the week and into the upcoming weekend. Could see more widespread mid/upper 60s or even lower 70s (interior Central Coast) by week's end. Forecast ensembles indicate high confidence in continued dry weather conditions through at least the next 10 days.


As of 03:31 AM PST Tuesday, For the 12Z TAFs. Patchy low clouds are bringing LIFR conditions to terminals in the North Bay, with MVFR conditions around the Monterey Bay. It will likely take at least until 18Z to get any clearing to VFR for these terminals. The rest of the stratus lurks out over the ocean. The remainder of the area if VFR, staying that way through Tuesday. A FEW low clouds may pass near terminals Tuesday morning but not expecting impacts. Breezy northwest winds Tuesday afternoon before diminishing in the evening. As high pressure grows, low clouds return to the North Bay terminals and Monterey Bay terminals overnight into Wednesday with a slight chance for them to spread into the SF Bay.

Vicinity of KSFO, Stratus clouds lurk just on the west side of the peninsula, but other than a FEW/SCT low clouds conditions are forecast to remain VFR Tuesday. Winds are light and will become breezy out of the northwest around 10 knots in the afternoon. As winds diminish, there's a chance for some low clouds to move into the bay Wednesday morning, but for now, there was too low confidence to add it to the TAF but will be monitored.

KSFO Bridge Approach, Similar to KSFO.

Monterey Bay, MVFR conditions as stratus clouds have developed over the terminals. Expect them to linger through most of Tuesday morning. Models are indicating some clearing Tuesday afternoon as northwest winds become breezy; however, the clouds should return quickly after 00Z with chances of IFR conditions into Wednesday morning.


As of 02:34 AM PST Tuesday, Moderate northwest winds will increase Tuesday afternoon and into the evening, becoming hazardous for smaller vessels through Wednesday, mainly over the outer waters. The west-northwest swell with a moderate period continues through the forecast period.

Watches, Warnings, Advisories

Today, sca, pt arena to pigeon pt 10-60 nm from 3 pm

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