Marine Weather and Tide Forecast for San Mateo, CA

UPDATE
Issued at 717 AM PDT Wed May 13 2026

Stratus continues to linger across the SF Bay Area and Central Coast as a decaying cold front moves across the region, helping to mix out the lower layers. Breezy winds continued overnight and into the morning across favored ridgelines and coastal regions, with the winds expected to pick up through the day.

DialH

SHORT TERM
Issued at 1204 AM PDT Wed May 13 2026 (Today and tonight)

A disjointed marine layer is trying to reform overnight per satellite fog product. Where it is reforming it's rather deep at 1500-2000 ft. The complicating factor in development of the marine layer is the passing upper low well to the north in OR and a trailing vort max/shortwave trough passing over region. Lastest guidance continues to advertise some expansion of the marine layer through sunrise, but it never completely fills in the "standard" marine layer footprint. Morning low clouds will give way to afternoon sunshine, even the coastal locations. The coastal clearing today will be enhanced by the increasing northerly gradients and stronger winds. SFO-ACV will ramp up to over 5 mb, which is decent. Winds will be strongest over the coastal waters this afternoon and immediate coastline with gusts of 25-45 mph possible. Despite some sunshine temperatures will be close to or below normal for mid May with highs in the 60s to lower 70s coast/bays and 70s to mid 80s inland. It will be the coldest day of the next seven.

For tonight, not expecting a ton of marine stratus due to lingering stronger northerly flow and a departing upper level trough.

LONG TERM
Issued at 1204 AM PDT Wed May 13 2026 (Thursday through Tuesday)

By Thursday zonal flow develops over the region as high pressure begins to build, but is tampered by a trough near the Gulf of AK.
The semi-zonal flow will continue through Friday. As such, a gradual warming and drying trend will develop. A blip in the longwave pattern with a sagging upper level trough over CA on Saturday will drop temperatures back to near or below seasonal averages. The sagging trough deepens and develops a low that sweeps into the Great Basin. Why is this important for our area? Pattern recognition points to bursts of offshore flow over the higher terrain each night into morning hours beginning Sunday into next week. This will lead to marginal humidity recovery at night. Not a big fire concern at this point, but something we'll need to monitor over the next few days. ERC charts are catching on with a trend line back toward daily maxes.

More uncertainty for next week is around max temps Mon/Tue. While the longwave pattern shows troughing to the east and a ridge over the EPac it doesn't scream heat. The NBM is showing some rather warm temps with interior 90s again. Call it recency bias, but 850 mb not 20C+ gives me pause on max temps from the NBM. Other ens guidance is on the colder side and did verify better during our most recent warm spell. That being said, we'll need to watch this as well and trend temps down if needed
Stay tuned

AVIATION
(12Z TAFS)
Issued at 610 AM PDT Wed May 13 2026

AVIATION
Widespread moderate winds will impact the Bay throughout the day due to the tightening pressure gradient driven by the dry cold front passing through our region. Currently MVFR-IFR ceilings for most terminals that will scatter out by 17-19Z (10am-12pm PDT). Model guidance is not giving a strong signal on the return of a expansive marine layer tonight. There may be some low-level stratus in the coastal areas this evening though the marine layer is not expected to expand far inland.

Vicinity of SFO...Borderline MVFR-IFR ceilings persist through late morning Wednesday with moderate to fresh breezes. Wednesday afternoon will bring gusts up to 30kts that will continue through the evening. VFR conditions are expected throughout the day with some low-level clouds beginning to creep in overnight. Winds should also ease overnight.

SFO Bridge Approach...Current satellite (13Z) is showing a gap amidst surrounding MVFR-IFR ceilings. Should become completely VFR by the late morning and winds should match the general pattern of KSFO with gusts up to 25kts.

Monterey Bay Terminals.. MVFR ceilings persist through Wednesday morning and are expected to mix out by the afternoon. Westerly winds are also expected to increase through the day with VFR conditions forecast through the end of the TAF period. Low to medium confidence that a prominent marine layer will re-develop Wednesday evening as we are currently in a transitional period. GFS LAMP and MOS guidance are leaning more pessimistic meanwhile HRRR is leaning towards a few to scattered stratus deck. KMRY will continue to experience low clouds Wednesday evening due to its proximity to the coast, though it is unclear whether KSNS will join them.

MARINE
(Tonight through next Sunday)
Issued at 443 PM PDT Tue May 12 2026

Hazardous marine conditions develop midweek and will continue into next week. Winds increase through the remainder of the week with strong to near gale force winds and occasional gale force gusts Wednesday and Thursday. Wind driven seas will build to between 10 to 12 feet Wednesday and Thursday. Surface high pressure will then strengthen over the eastern Pacific Friday into next week.
This will result in a strong coastal jet, widespread gale force to potentially severe gale winds, and very high, wind driven seas between 12 to 17 feet expected.

MTR WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Thursday for Mry Bay.

Small Craft Advisory until 9 AM PDT Thursday for Pt Arena to Pt Reyes 0-10 nm.

Gale Warning from 9 AM Thursday to 3 AM PDT Friday for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

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

Small Craft Advisory until 3 AM PDT Friday for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM.

Small Craft Advisory until 9 AM PDT Thursday for Pt Arena to Pt Reyes 10-60 NM.