Marine Weather and Tide Forecast for Belmont, CA

SHORT TERM
(Today and Tuesday) Issued at 100 AM PDT Mon May 12 2025

A cold front with upper-level support will be the name of the game over the next two days. Said cold front remains just off the California Coast with rain just beginning to reach the ground in Mendocino County (just to the north of our CWA). Cloud cover and light rainfall will expand in coverage through the morning.
Rainfall totals will have a northwest to southeast gradient of 0.20" to 0.00" respectively with locally higher totals in the higher terrain of the Bay Area. Interior Monterey and San Benito Counties may not receive measurable precipitation, but light drizzle can be expected, especially in the higher terrain with the help of orographic lift. Strong and gusty onshore winds will continue with the strongest winds expected in the higher terrain, gaps, and passes where gusts up to 40mph are expected. Widespread gusts of 20-30mph can be expected elsewhere. The post-frontal environment will have a low probability (<15%)/high impact threat for thunderstorms. If a thunderstorm were to develop the threats include lightning, small hail, and locally heavy rainfall and gusty winds.

LONG TERM
(Wednesday through Sunday) Issued at 100 AM PDT Mon May 12 2025

Heights will be slow to rebuild Wednesday as the open wave exits to the east. There still remains uncertainty in the extended forecast as an upper-level shortwave ridge building into the Eastern Pacific Ocean Thursday quickly gets flattened by an upper-level shortwave trough in the Gulf of Alaska by Friday. These two features will propagate through the upper-level pattern and are resulting in 33% of global ensemble members suggesting an inside slider like pattern setting up over the weekend with the ECMWF and Canadian as the primary drivers. As of now they are forecasting the upper- level low only reaching the Northern Great Basin and remaining progressive. Any further digging, strengthening, or westward solution will likely result in more impacts if it were to come to fruition.

AVIATION
(12Z TAFS)
Issued at 452 AM PDT Mon May 12 2025

MVFR CIGs are building as showers enter the area. These shower chances become widespread through the morning as CIGs become more consistent. Moderate to breezy southwest winds will move along the edge of the front with the better chances for rain. Winds shift to become more westerly after the frontal passage and become more gusty. CIGs scatter into the afternoon with some lingering scattered showers lasting into the late afternoon and evening. Winds become light into the evening and CIGs reestablish at HAF, LVK, SJC and the Monterey Bay terminals.

Vicinity of SFO...Spotty showers become more consistent into the mid morning as southwest winds increase. Rain rate stay light so visibilities don't look to be largely affected. The front passes in the late morning with breezy to gusty west winds building behind it and CIGs will scatter. Lingering spotty showers last through the afternoon into the evening. Expect winds to reduce into the night and become light by Tuesday morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Light winds and MVFR CIGs last through the morning before CIGs scatter and winds become moderate to breezy for the afternoon. Scattered light showers pass near the terminals in the mid morning, with spotty chances lasting through the evening.
Winds reduce into the evening and MVFR CIGs rebuild into the night.



MARINE
(Today through Saturday)
Issued at 452 AM PDT Mon May 12 2025

A cold front will bring light rainfall and fresh westerly breezes today. There's around a 10% chance for thunderstorms today into tomorrow which would pose the threats of lightning, small hail, and locally heavy rainfall and gusty winds. Hazardous marine conditions are expected through the week with rough seas and gale force gusts expected.

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

Small Craft Advisory from 9 AM this morning to 9 AM PDT Tuesday for Pt Arena to Pt Reyes 10-60 NM.