Marine Weather and Tide Forecast for Castro Valley, CA

UPDATE
Issued at 846 AM PST Tue Mar 3 2026

Low clouds will clear out later this morning and give way to mostly sunny skies this afternoon. The one exception will be around the San Francisco Peninsula where clouds may linger throughout much of the day. With clearing skies, expecting afternoon temperatures to warm into the upper 50s to lower 60s near the coast and mid to upper 60s across much of the interior (and the Santa Cruz area). Isolated spots are forecast to exceed 70 deg F this afternoon, especially across the interior valleys of the Central Coast, areas around Gilroy, Hollister, and Concord, and interior valleys of Napa County.
These areas have a greater than 70% probability of exceeding 70 deg F. No updates are anticipated at this time.

RGass

SHORT TERM
Issued at 121 AM PST Tue Mar 3 2026 (Today and tonight)

With the lunar eclipse underway there is a lot of focus on the cloud cover this morning. The situation is pretty complex.
Boundary layer averaged winds are actually from the NE, but surface winds are still onshore for most locations. The SFO-SAC gradient is +0.9 mb (onshore), but the SFO-WMC gradient is -1.1 mb (offshore). The marine stratus deck is becoming more organized, and it looks like a race against time for the remaining clear skies to stay that way before totality. The best chance is in the interior East Bay and Monterey County, but even those aren't guaranteed as the stratus closes in over the next hour.

A short wave ridge will dominate the pattern today. This will bring afternoon temperatures 2-5 degrees warmer than yesterday. On the other hand, the ridge and warmer air will help support a thermal trough near the coast. This will bring an enhanced sea breeze that will be noticeable for coastal communities. After the clouds burn off late morning it will be a warm, clear, and breezy afternoon.

LONG TERM
Issued at 121 AM PST Tue Mar 3 2026 (Wednesday through Monday)

Another trough moves through on Wednesday, dragging a cold front across the surface. Overcast skies will be a clear sign of the front passing through the afternoon and evening. The rain chances and amounts were already low, but have decreased thanks to the dry air mass. The real story with this front is wind. Very strong high pressure will build behind the front, reaching around 1035 mb in the Eastern Pacific. While high pressure is the norm in the Eastern Pacific, 1035 mb is roughly 15 mb or 1.5 standard deviations above normal for this time of year. The gradient between this high pressure and the ~1007 mb low that supported the cold front will support strong NW winds starting Wednesday and continuing through Friday night. Gusts will very likely reach gale force along the coast and across higher terrain. The wind direction will gradually shift from NW onshore flow to northerly or NE offshore flow as the 500 mb pattern evolves into an inside slider by Saturday. The combination of high pressure and offshore winds will bring a warming trend through the weekend, with most areas easily reaching the 70s from Saturday through Monday. The forecast uncertainty grows by the middle of next week. Most ensemble solutions keep a general ridging pattern, but a few outliers disagree and bring a more active pattern. The most likely outcome is a very dry first half of March.

AVIATION
(18Z TAFS)
Issued at 934 AM PST Tue Mar 3 2026

Lingering MVFR-LIFR stratus and fog continue across the Bay Area and the southern Monterey Bay region, with further dissipation expected through the next few hours barring the immediate coast near Point Reyes and the western side of the San Mateo Peninsula, where the stratus could linger through the day. A light to gentle onshore flow will develop this afternoon, lingering into the evening as the stratus returns to the valleys. The passing of a cold front may result in some sprinkles overnight into Wednesday morning, but the main impact will be to maintain a moderate northwest breeze through the night before winds increase Wednesday afternoon, after the end of the 24-hour TAF period.

Vicinity of SFO... MVFR-IFR stratus lingers for the next couple of hours. A gentle to moderate west-northwest breeze will develop through the afternoon and evening hours, with winds remaining gentle overnight as MVFR stratus returns to the terminal. Stronger winds are expected to develop on Wednesday as a cold front passes.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... Lingering stratus should dissipate within the next hour. A gentle northwest breeze should develop in the afternoon, with light winds this evening as MVFR stratus returns overnight. Winds begin to increase from the north towards the end of the TAF period, with clearing of the stratus around or just after the end of the TAF period.

MARINE
(Today through Sunday)
Issued at 846 AM PST Tue Mar 3 2026

Expect hazardous marine weather conditions Wednesday through Friday. A moderate northwest breeze today increases to a strong northwest breeze on Wednesday and near gale force winds by Thursday. These winds will build very rough seas of 12 to 15 feet across exposed waters Thursday through Friday.

MTR WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PST Wednesday for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Reyes to Pigeon Pt 0-10 nm.

Gale Watch from Wednesday evening through Thursday morning for Pigeon Pt to Pt Pinos 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

Small Craft Advisory from 3 PM this afternoon to 3 PM PST Wednesday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

Gale Watch from Wednesday afternoon through Thursday morning for Pt Pinos to Pt Piedras Blancas 0-10 nm.

Gale Watch from Thursday morning through late Thursday night for Pt Arena to Pt Reyes 10-60 NM.

Gale Watch from Wednesday evening through late Thursday night for Pigeon Pt to Pt Pinos 10-60 NM.