Marine Weather and Tide Forecast for Mountain House, CA

UPDATE
Issued at 906 PM PDT Thu Jun 19 2025

We recorded much cooler high temperatures across the more inland areas today. It was around 5-10 degrees cooler for the North Bay Valleys, San Jose, and interior Monterey Co. The biggest departures included Concord, Redwood City, and Livermore all of which were around 20 degrees cooler as the onshore flow increased today.

In spite of these cooler conditions, humidities away from the coast only saw small improvements. That, mixed with our stronger winds still keeps the interior (specifically the higher elevations) in fire weather danger. Luckily, the humidities continue to improve into the weekend, and the winds back off in the second half of the weekend. Until then, sure to stay fire weather aware!

-Murdock

SHORT TERM
(This evening through Friday)
Issued at 202 PM PDT Thu Jun 19 2025

Satellite imagery reveals stratus clouds lingering across the western San Mateo Peninsula and patches of the Monterey Peninsula.
These patches of cloud may be slow to mix out this afternoon, and some inland stratus development is possible tonight through Friday morning. A developing upper level low off the coast of British Columbia is approaching the Pacific Northwest, with an associated cold front cooling temperatures across the region by as much as 10 degrees compared to this time yesterday. Highs will reach the middle 70s to lower 80s in the inland valleys, the lower to middle 90s in the southern reaches of Monterey and San Benito counties, the 60s along the Bayshore, and the middle 50s to lower 60s along the Pacific coast. Coastal drizzle is possible tonight into Friday morning, with low temperatures generally in the middle 40s to the middle 50s. Friday's high temperatures will generally be similar to today's with further cooling in the inland valleys of the North Bay and Central Coast, with high in the upper 60s to the middle 70s across the inland valleys and the lower to middle 80s in the southern reaches of Monterey and San Benito Counties.

The deepening upper level low to the north is causing a tightening of the pressure gradient across the region, leading to strong and gusty northwest winds developing through the day and lasting into Friday. Gusts for this afternoon and evening will reach 25 to 40 mph across the region, with the highest gusts along the coast, across the ridgelines, through the gaps and passes, and within the Salinas Valley. Particularly favored locations such as the Altamont Pass and favored locations in the Salinas Valley may get gusts up to 50 mph this afternoon and evening.

LONG TERM
(Friday night through next Wednesday)
Issued at 202 PM PDT Thu Jun 19 2025

The strong gusts will continue into Saturday with the winds expected to peak Friday evening. Through the weekend, the low pressure system will begin to split, thus slackening the pressure gradient, with some of its energy moving off into the Canadian prairie provinces, leaving behind a more open trough across California. This open trough will stick around for a few days with a strong upper level ridge over the eastern United State blocking its path to the due east. As a result, there will be a gradual warming trend into the early part of next week, but nothing resembling a heat wave is expected, with the high temperatures generally around seasonal averages of the lower to middle 80s inland and the upper 60s to the middle 70s along the Bayshore, while cooler conditions continue along the Pacific coast with highs temperatures in the upper 50s to middle 60s.

AVIATION
(06Z TAFS)
Issued at 935 PM PDT Thu Jun 19 2025

Cold air advection, a deepening marine layer, upsloping winds and radiative cooling favor coastal stratus /MVFR/ redevelopment with local inland intrusions tonight and Friday morning. Drier air arrives from the north and northwest Friday with clearing /VFR/ from north to south. Areas of strong and gusty west to northwest winds continue through the evening, with some relaxation in winds overnight then strengthening west to northwest winds redeveloping Friday during the day. Based on recent HRRR output, expect mainly VFR except areas MVFR ceilings along the immediate coastline Friday night and early Saturday morning.

Vicinity of SFO...Gusty onshore winds gradually easing overnight then west wind strengthening again Friday with gusts to 35 knots.
BKN-OVC ceiling prevailing tonight to 15z-16z Friday. Radiative cooling tonight will help restore a stratus feed to SFO for the overnight.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Onshore winds, cold air advection, nocturnal cooling and a deepening marine layer support MVFR stratus ceilings tonight and Friday morning. Stratus mixing out to VFR by late Friday morning and SCT-BKN low clouds return Friday evening and night. Onshore winds 10 to 15 knots with occasional gusts to 20 knots.

MARINE
(Tonight through next Wednesday)
Issued at 906 PM PDT Thu Jun 19 2025

Gale force winds will bring fresh swell, steep winds waves, and hazardous conditions to the coastal waters through Friday. Onshore flow will bring windy conditions to the bays as well. Winds will be strongest across the outer waters and for the inner coastal waters north of Point Reyes and south of Point Sur, where coastal jets are expected to develop. Significant wave heights build to 10 to 12 feet across the coastal waters Thursday into the weekend before abating early next week.

FIRE WEATHER
Issued at 202 PM PDT Thu Jun 19 2025

Elevated fire weather conditions are setting up today across the interior, with widespread RH values below 30% observed across the interior of the East Bay south through the Gabilan Range, along with the Santa Lucia mountains, combined with gusts of 20 to 25 mph.
Gusts are expected to increase to 25 to 40 mph across the interior later this afternoon and evening, with strong gusts resuming Friday and Saturday afternoon. Brief periods of critical fire weather conditions are possible with daytime relative humidities of 15 to 25% in the interior. However, continuing marine layer influence, especially during the night, and the fact that winds remain onshore, mean that widespread critical fire conditions do not develop across the district. Gusty winds begin to subside on Saturday, but the upper level pattern will lead to more northerly winds developing across the region. As with today's fire weather threat, widespread critical fire weather conditions are not expected within the district, although the fire weather threat will increase for areas closer to the Central Valley. The fire weather threat will continue to diminish Sunday into the early part of next week with the gusty winds further relaxing, although humidity values in the interior will be slow to rise.

DialH

MTR WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Friday for Mry Bay-SF Bay N of Bay Bridge.

Small Craft Advisory from 1 PM to 9 PM PDT Friday for Mry Bay-SF Bay N of Bay Bridge.

Gale Warning until 9 PM PDT Friday for Pigeon Pt to Pt Pinos 0- 10 nm-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.

Gale Warning until 3 PM PDT Friday for Pigeon Pt to Pt Pinos 10- 60 NM.