Marine Weather and Tide Forecast for Napa, CA

UPDATE
Issued at 853 PM PDT Thu Mar 19 2026

The forecast remains mostly on track, however adjusted max temperatures for portions of the South Bay that haven't been getting as hot as their surrounding areas, likely due to the seabreeze not making it as far south as central San Jose and mixing the warmer inversion temperatures just above down to the surface. The Heat Advisory will expire at 8 PM PDT tomorrow evening, and we're currently not anticipating extending it into the weekend. Despite the cool down of about 10 degrees area wide on Saturday, max temps will remain 10-15 degrees above normal through the extended forecast.

SHORT TERM
Issued at 105 PM PDT Thu Mar 19 2026 (This evening through Friday)

Definitely a day of nuanced details and micro-climates around the Bay Area and Central Coast. In the big picture it's still hot around the region with temperatures well above for late March. The details however show many locations are running colder than yesterday and some of these locations will fall short of their forecast high temperature. The shallow marine layer from early this morning was enough to cause havoc on max temps with any marine influence. All that being said, did tweak a few temperatures this afternoon, but didn't completely give up on hope for a warm up. A quick shift of the wind direction could allow for a late day bump in temps. The airmass does support it as the OAK sounding was 19.55C at 850mb at 12Z this am.

For tonight through Friday...marine layer from this morning has faded and pretty much dissipated per satellite. Offshore flow is gradually developing just above the surface. This will persist overnight and actually strengthen a bit leading to better mixing and some drying flow in the BL. Hi-res guidance shows this as well with lower moisture at the surface. Some patchy clouds are possible near the coast, but thinking less than last night.
Friday will be a transition day as the anomalously upper ridge begins to slowly ease eastward. 500mb heights may decrease slightly, but 850mb will likely reach their peak. As such, inland areas have the potential of seeing some of their warmest temps yet. Just like today however, coastal areas will be tricky again with subtle temp differences due to marine influence late in the day. Will keep Heat Advisory as is for now. Even if a few spots near the coast/bays fall a little short of forecast highs heat impacts are a cumulative effect.

LONG TERM
Issued at 105 PM PDT Thu Mar 19 2026 (Friday night through next Wednesday)

The large area of high pressure continues its eastward push Friday night into Saturday as an upstream trough/cold front moves in. At the surface, local WRF model shows the rebuilding of the marine layer Friday night. The cold front is expected to push through day putting an end to the heat wave and bringing much needed relief. The fropa will bring a 5 to 10 degree drop on Saturday with an additionally 5 degrees on Sunday. Despite the temp drop for Saturday and Sunday, temperatures will still be well above normal for March. Temperatures moderate through the first half of next week, but stay above normal with zonal flow over the region. Previous forecast had precip brushing the N Bay around the 25th of March, but latest guidance continues with a drier solution. If this chance of precip is looking less when does confidence increase? Longer range ensemble forecast show a few members producing rain around the beginning of April. As they say, April showers bring May flowers. We'll see...

AVIATION
(06Z TAFS)
Issued at 951 PM PDT Thu Mar 19 2026

VFR. Model guidance is less confident that a shallow marine layer will return tonight with the most recent buoy observations supporting this change. Winds are largely easing with most sites becoming more variable overnight. Moderate onshore winds (10-15 knots) are expected tomorrow afternoon/evening before weakening again tomorrow night. Moderate confidence that a shallow marine layer (around 500 ft) will return Friday night into Saturday.
Current HRRR and WRF guidance support more widespread stratus coverage tomorrow night starting around 06Z (potentially earlier for coastal sites).

Vicinity of SFO...VFR. Winds ease overnight before moderate onshore winds return late tomorrow afternoon and continue into the evening.
Initial guidance is suggesting stratus will reach SFO between 09-12Z Saturday night with the potential for IFR CIGs to develop.
Confidence is currently low to moderate that stratus will make it to SFO (slightly higher for OAK) but guidance is signaling increasing potential for the marine layer and stratus to return tomorrow night.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR. Removed the mention of stratus for coastal sites given that marine conditions are not supportive of it developing and models have backed off. Confidence is slightly higher in the marine layer and stratus returning Friday night into Saturday as a shallow (500 ft) marine layer looks to develop. A SE drainage wind will develop at SNS early Friday morning before winds shift onshore for both airports during the afternoon/evening hours.

MARINE
(Tonight through next Wednesday)
Issued at 951 PM PDT Thu Mar 19 2026

A gentle to moderate northwesterly breeze continues across the coastal waters. Northwest winds start to increase tonight across the outer waters before spreading across the inner waters Friday into the weekend. Hazardous seas return by Friday night due to strengthening winds. Gale force gusts are expected across the outer waters late Saturday into early Sunday.

CLIMATE
Issued at 1021 PM PDT Thu Mar 19 2026

The following are the record high temperatures at the long term sites for March 20th.

Location Mar 20

Santa Rosa 84 in 2004 San Rafael 82 in 1960 Kentfield 82 in 2001 Napa 86 in 2004 Richmond 81 in 2004 Livermore 87 in 1915 San Francisco 78 in 2004 SFO Airport 78 in 2004 Redwood City 82 in 2004 Half Moon Bay 75 in 2010 Oakland Museum 78 in 2001 San Jose 78 in 2004 Salinas Airport 80 in 1934

The following are the record high temperatures at the long term sites for the entire month of March.

Location

Santa Rosa 92 March 19, 2026 San Rafael 89 March 19, 2026 Kentfield 91 March 28, 1923 Napa 92 March 17, 1914 Richmond 88 March 18, 2026 Livermore 90 March 25 and 26, 2025 San Francisco 87 March 11, 2005 SFO Airport 85 March 25, 1952, March 17, 2026, March 19, 2026 Redwood City 93 March 17, 2026 Half Moon Bay 83 March 31, 2000 and March 17, 2004 Oakland Museum 89 March 17, 2026 San Jose 89 March 14, 2015 Salinas Airport 93 March 18, 2026

MTR WATCHES/WARNINGS/ADVISORIES
CA...Heat Advisory until 8 PM PDT Friday for CAZ006-502>506-508>510- 512>518-528>530.

PZ...Small Craft Advisory from 3 PM Friday to 9 AM PDT Saturday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

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