Swell Matrix

Area Forecast Discussion

National Weather Service San Francisco CA

413 am PDT Wed apr 15 2026

Short Term

, Issued at 1214 AM PDT Wed Apr 15 2026 (Today and tonight)

A weak fetch of onshore flow at the surface is struggling to maintain patches of low stratus along the SF Peninsula and the Salinas Valley late tonight. Progressive ridging aloft has resulted in very dry air in the mid/upper levels, that will persist into the early afternoon. A sharpening trough to our north will reach the North Bay tonight behind the exiting ridge, with a weak associated moisture gradient out ahead. However, increasing low and mid-level onshore flow will result in a moderate increase in cloud cover this afternoon. Breezy west winds out ahead of the dry surface boundary will eventually become northerly overnight as the upper trough pivots east and south. Temperatures today will be similar to yesterday, maybe a few degrees warmer inland where less cloud cover is expected. Temperatures tonight will still be on the cool side across the North Bay and higher elevations across the East Bay Hills with weak cool advection behind the dry surface boundary late tonight.

Long Term

..issued at 1214 AM PDT Wed Apr 15 2026 (Thursday through Tuesday)

Gusty offshore flow will gradually spread south across our area after sunrise Thursday. The strongest winds will be at higher elevations, especially in the North Bay and East Bay Hills, but not expected to exceed 40mph. Temperatures on Thursday will be similar to Wednesday, right around normal in the 60s to low 70s. Temperatures overnight Thursday into Friday will be chilly once again with cooler air aloft lingering behind the exiting trough and surface wind fields easing simultaneously under clear skies leading to efficient radiational cooling. Thursday night should be an excellent night for star gazing. Progressive, yet high amplitude ridging bumps temperatures up Friday and Saturday, before the next trough arrives from the Pacific Northwest on Sunday. Consensus diverged in deterministic guidance from this time last night, thus confidence in timing, location and intensity of rainfall is still low. However, it still looks most of our area will see at least some light rain Sunday through Tuesday.

Aviation

(12z TAFS) Issued at 413 AM PDT Wed Apr 15 2026

There are a few areas of low clouds /VFR-MVFR/ including patchy mist/fog /IFR-LIFR/ this morning. Conditions improving to VFR today. Low clouds /MVFR/ increasing ahead of a cold front from the northwest tonight and early Thursday morning.

Vicinity of SFO, VFR-MVFR. West wind increasing to 15 to 20 knots in the afternoon, continuing tonight and Thursday morning.

SFO Bridge Approach, Similar to SFO.

Monterey Bay Terminals, VFR-MVFR. West winds 5 to 15 knots.

Marine

(today through Monday) Issued at 353 AM PDT Wed Apr 15 2026

Fresh northwest breezes and moderate seas will continue over the coastal waters through today. A mostly dry cold front will push through tonight followed by gusty northwesterly winds Thursday. These winds will build rough seas of 10-12 feet across the exposed coastal waters. Winds will ease back to moderate northwest breezes Friday through Saturday, allowing seas to gradually subside.

Watches, Warnings, Advisories

Ca, None. PZ, Small Craft Advisory from 3 PM to 9 PM PDT Thursday for Mry Bay.

Small Craft Advisory from 9 PM this evening to 9 PM PDT Thursday for Pigeon Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm.

Small Craft Advisory from 3 PM this afternoon to 9 PM PDT Thursday for Pt Reyes to Pigeon Pt 0-10 nm.

Small Craft Advisory until 3 AM PDT Friday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

Small Craft Advisory from 9 PM this evening to 3 AM PDT Friday for Pt Arena to Pt Reyes 10-60 NM.

Small Craft Advisory from 3 AM Thursday to 3 AM PDT Friday for Pigeon Pt to Pt Pinos 10-60 NM.

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