Marine Weather and Tide Forecast for Millbrae, CA

UPDATE
Issued at 937 AM PDT Fri May 23 2025

As we head into this holiday weekend we have two things to keep in mind. The first is that although air temperatures will be warm, ocean temperatures are still chilly in the low to mid 50s. These temperatures can cause incapacitation within a few minutes for even experiences swimmers and result in cold water drowning. The second is a reminder that a lot of our smaller fuels (i.e. grasses) are either dry or in the process of drying out. If you are outdoors using a campfire or some sort of stove remember to exercise caution and prevent sparks from flying. One less spark, one less wildfire! Otherwise the forecast remains on track with seasonal temperatures and breezy afternoon/evening winds.

SHORT TERM
(Today and tonight)
Issued at 358 AM PDT Fri May 23 2025

Subtle upper level trough set to move through today amid a robust NW flow regime, which has been keeping us rather breezy through this week. Today will largely be a fair weather day aside from the breezy conditions this afternoon along the coast and NW-SE oriented valleys. Cooler temps as well today just a few degrees below seasonal normals across the region. As the recent few days have shown, grasses and fine fuels are cured and ready to burn, despite onshore wind and relatively cool temps. It won't take much for grasses to light up and spread quickly while the winds are breezy.

LONG TERM
(Saturday through Thursday)
Issued at 358 AM PDT Fri May 23 2025

Another breezy day Saturday, albeit less so. Gust NW flow lingers into the weekend but continues to wind down as high pressure builds aloft. From Saturday, we'll kick off a subtle warming trend that lasts through the extended period. Ensemble guidance basically advertises a subtle ridge-trough-ridge pattern with a stronger ridge building over the western US into Canada by the end of the month. It is advertised well by cluster analysis (high confidence) that there is a high likelihood of above average temperatures by the end of the current 7 day forecast period.
We'll reassess when we get closer, but until then, heavier fuels and timber and actually in decent shape in terms of moisture. As previously mentioned, however, grasses are becoming very dry as we have seen with a few grass fires over the past few days. Now is the time in the season to prepare before we have anything more to worry about. Understand your risk, evaluate your defensible space, stay weather aware, and remember, "one less spark!"

AVIATION
(12Z TAFS)
Issued at 254 AM PDT Fri May 23 2025

A few areas of coastal stratus /MVFR-IFR/ are forming early this morning, including some inland formation of stratus clouds /MVFR/ as well, otherwise it's VFR. The northerly and westerly pressure gradients (and winds) will be weighted more equally today with the gradients approx 3 to 4 mb from ACV to SFO and from SFO to SAC. Surface to near surface cool air advection predominates from the San Francisco Peninsula over to the East Bay and the South Bay to the northern Monterey Bay Area early this morning which is helping to bring the air to saturation forming areas of stratus.
During the daylight hours, mixing will increase and reduce the areal coverage of stratus, then with cooling tonight and early Saturday coastal stratus and fog /IFR-LIFR/ will develop; the lower level temperature inversion strengthening and compressing the marine layer.

Vicinity of SFO...Gusty west wind will transport stratus /MVFR- IFR/ to the terminal this morning until mixing out to VFR at 16z.
West wind gusty today with gusts near 30 knots during the afternoon and early evening. HRRR output shows stratus /IFR/ returning tonight and Saturday morning. The marine layer will compress tonight and Saturday morning increasing the probability that the stratus ceiling will be IFR.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Stratus /MVFR-IFR/ is continuing to form early this morning. MVFR-IFR until later this morning with stratus then mixing out to MVFR-VFR for the afternoon, then HRRR output shows stratus /IFR/ redeveloping this evening and continuing overnight to Saturday morning. Onshore winds 5 to 10 knots except 10 to 20 knots in the afternoon and early evening.

MARINE
(Today through Wednesday)
Issued at 937 AM PDT Fri May 23 2025

Hazardous marine conditions continue across the waters as strong northwesterly breezes with near gale to gale force gusts and rough seas persist. Fresh to strong northwesterly breezes and moderate to rough seas will prevail through Monday.

MTR WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for SF Bay N of Bay Bridge.

Small Craft Advisory until 9 PM PDT this evening for Mry Bay- Pigeon Pt to Pt Pinos 0-10 nm.

Gale Warning until 3 AM PDT Saturday for Pt Arena to Pt Reyes 0- 10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

Small Craft Advisory until 9 PM PDT Saturday for Pigeon Pt to Pt Pinos 10-60 NM.