Marine Weather and Tide Forecast for Mountain View, CA

UPDATE
Issued at 910 PM PDT Thu May 22 2025

Generally clear skies across most of the region, but for the first time in a couple of nights, satellite imagery depicts the formation of patchy stratus along the western slopes of the Marin coastal ranges and the San Mateo hills, as well as a patch near Bodega Bay. These are indicative of a rebuilding marine layer.
Combined with cooler temperatures and continuing onshore flow, this will help alleviate fire weather concerns in the interior, particularly as overnight humidity recoveries will improve through the week. Unfortunately, there was a grass fire that did pop up at the eastern edge of Alameda County today. Forward progress has been stopped, but this is a reminder that the fire season is quickly approaching. As for the forecast, no changes at this time.

DialH

SHORT TERM
(This evening through Friday)
Issued at 252 PM PDT Thu May 22 2025

Strong onshore winds gusting between 30 to 35 mph along the coast, mountain gaps and passes, and northwest/southeast oriented valleys continue overnight into Friday morning. Elevated fire weather concerns persists through this evening with dry conditions across the interior (relative humidity values in the 15 to 30% range). The primary concern continues to be for areas where grasses are cured (grasses have browned/dried out). An approaching upper level trough will help to bring in more moist air and deepen the marine layer to 1500 ft tonight. This increase in moisture will ease the elevated fire concerns that we have seen over the last few days with overnight relative humidity values increasing to 70-90% across the interior. Patchy stratus cover will return to coastal areas and the San Francisco Bay region overnight but is not expected to be widespread. Breezy winds will continue again on Friday, but, they will be weaker than those observed on Wednesday/Thursday. Winds are expected to gust between 20-25 mph on Friday along the coast, through the valleys, and across the elevated terrain. Temperatures across the North Bay hold steady in the upper 70s on Friday while temperatures across the rest of the Bay Area will drop by about 5 degrees. This will bring most locations across the South Bay and East Bay into the upper 60s to mid 70s and into the 50s to 60s along the San Francisco Peninsula. Residents of the interior Central Coast may feel a more substantial drop, with highs to drop from the upper 80s to low 90s on Thursday to the low to mid 80s on Friday. If you find yourself thinking that this is a bit chilly for May, you would be correct in that Friday's forecast temperatures are expected to be around 10 degrees below normal for this time of year.

LONG TERM
(Friday night through next Wednesday)
Issued at 252 PM PDT Thu May 22 2025

Surface high pressure and a positively tilted upper level trough will build in over the weekend into next week over the West Coast.
This will help to keep our temperatures and winds in a fairly stable pattern this week. For temperatures, highs will stay in the 70s to low 80s across the interior and upper 50s to mid 60s along the coastline. Diurnally breezy winds between 20 to 30 mph will continue across the coastline, valleys, and across the elevated terrain through Wednesday. Overall this upcoming week looks pleasant with temperatures running around 10 degrees below normal. That will change by late next week with temperatures looking to rise again and CPC forecasting above normal temperatures from the end of May into June. In the longer run, both the GFS and ECMWF are starting to generate a cut-off low oriented offshore to the southwest of the California coastline. While this is still a ways out, it may be worth keeping an eye on for the possibility of offshore winds across the CWA

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 257 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 until 3 AM PDT early this morning for SF Bay N of Bay Bridge.

Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for SF Bay N of Bay Bridge.

Gale Warning until 3 AM PDT early this morning for Mry Bay- Pigeon Pt to Pt Pinos 0-10 nm.

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

Small Craft Advisory until 9 AM PDT this morning for 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 Warning from 9 AM this morning to 3 AM PDT Saturday for 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 Warning until 3 AM PDT Saturday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

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