Marine Weather and Tide Forecast for Napa, CA

SHORT TERM
Issued at 1218 PM PST Sun Dec 7 2025 (This evening through Monday)

Today is looking to be very similar to yesterday, right down to the satellite imagery showing outgrowth from the Tule Fog across the Bay Area, slowly dissipating south of the Golden Gate and west of the Berkeley-San Leandro Hills and the eastern Santa Clara Mountains, and lingering across the North Bay and interior East Bay valleys.
Indeed, if you compared the current satellite image and the one from yesterday, you could only them apart by the lack of coastal stratus today. As a point of curiosity, while there are no radiosonde observations over the Central Valley, aircraft soundings from the region suggest that the saturated lower atmosphere -- the "Tule fog" layer, if you will -- extends 1500-2000 feet above the ground. The Central Coast remains mainly clear.

The remarkably similar evolution of the stratus from yesterday through today has lowered confidence in the clearing of stratus from the Santa Rosa Plain and the rest of the North Bay valleys. I've tamped down the high temperatures today even further in those regions, into the upper 40s to the lower 50s, and even then the expected highs are still a little warmer than the observed highs yesterday. Across the rest of the region, temperatures range from the middle 50s to lower 60s across the Bayshore, the Bay Area Pacific Coast and the Santa Clara Valley, while the sun-blessed Central Coast sees highs in the lower to middle 60s in the Monterey Bay region and the Hollister area, and the upper 60s to lower 70s inland.

Tomorrow, the ridge over the West Coast will strengthen and continue a general warming trend across the region. For the Central Coast, the temperature forecast should be similar to today's. The uncertainty increases across the Bay Area and especially in the North and East Bays, where the impacts of the building ridge on the Tule Fog remain uncertain. In general, a building ridge will tend to compress the inversion layer, and limit the extent that the Tule Fog can extend across the region. (We see this happen during our marine layer season as well, when building ridges compress the marine layer and prevent it from coming inland.) If the inversion layer does compress enough, the Tule Fog could find itself hitting a proverbial wall before it reaches the Bay Area. On the flip side, for those areas still impacted by the Tule Fog, ceilings and visibilities will tend to drop. This makes the temperature forecasts highly uncertain.
For now, tamped down the temperatures slightly so that the North and East Bay valleys see highs in the middle 50s to lower 60s, while the rest of the Bay Area valleys see highs in the lower to middle 60s, but this might be quite optimistic indeed.

LONG TERM
Issued at 1218 PM PST Sun Dec 7 2025 (Monday night through next Saturday)

Ridiculously resilient ridging will dominate the weather pattern through the rest of the week with the ridge crawling through the Western United States, such that over the next 6 days the ridge axis moves from just off the coast of the Pacific Northwest to the Oregon- Idaho border area. Over the Central Coast the impacts are most certain with a gradual warming trend in the forecast. The warmest days are expected Wednesday through Saturday with highs reaching the upper 60s to the middle 70s across the inland valleys. The Bay Area in general and the North and East Bay valleys in particular remain tied to the evolution of the Tule Fog. Impacts are expected to persist into the early part of the work week before diminishing with the continuing ridging across the region.

The pattern change for the middle of the month is beginning to come into the very end of the 7 day outlook. The early indications are pointing more towards a zonal flow pattern for the Western United States and any rain storms that develop generally being deflected into the Pacific Northwest. Beyond the 7-day outlook, the ensemble model clusters suggest that a return to a wetter pattern is possible around 9-10 days out, and the CPC's 8-14 day outlook shows a slight lean towards rainfall totals above seasonal averages for the third week of December
I have heard that before this month

AVIATION
(18Z TAFS)
Issued at 955 AM PST Sun Dec 7 2025

Tough forecast given the Tule fog and associated stratus have not been handled well by the models. In fact, most of them for today are fairly optimistic, which seems unlikely for much of our service Bay Area terminals. The marine layer looks to be 1000-1500ft, with the Valley being socked in as of this discussion. Expect cloudy conditions to prevail for most sites, with CIGS varying from LIFR to IFR. The exception might be KOAK, KSFO, and KSJC where onshore flow might be able to mix things out. Where skies are clear, KHAF, elevations above 1500ft, and the majority of the Central Coast, VFR conditions will prevail.

Vicinity of SFO...Low to medium confidence in the forecast here as most models have indicated some clearing by now and what we have seen so far is a slight lift in CIGs . Satellite imagery shows some clearing over the San Francisco Bay, but outside of that there doesn't appear to be much movement. The most pessimistic of forecasts looks to be the MOS guidance from the EC, which has loosely been incorporated in the TAF for clearing around 21Z. After that, opted to keep the previous forecaster's TAFs in shape if the onshore flow pans out. Should it not, and we stay socked in. The question if that happens will be how long do we stay with IFR cigs? Low to medium confidence on this forecast.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Light and variable offshore winds become onshore by this afternoon, before circling back to offshore or light variable tonight. No VIS or CIG concerns, thus VFR prevail.

MARINE
(Today through Friday)
Issued at 900 AM PST Sun Dec 7 2025

Moderate to fresh north to northwest winds hold for much of the waters today with strong gusts focused on the southern waters.
Moderate seas with wave heights 6 to 8 feet across the outer waters today, subsiding to around 4 to 6 feet for Monday. Winds increase on Tuesday, with strong to near gale force gusts possible for much of the waters. A new, long period northwesterly swell is anticipated by Wednesday of next week.

MARINE
(Tonight through next Friday)
Issued at 248 PM PST Sun Dec 7 2025

Moderate to fresh north to northwest winds hold for much of the waters through tonight with strong gusts focused on the southern waters. Moderate seas with wave heights 6 to 8 feet across the outer waters will subside to around 4 to 6 feet for Monday. Winds increase on Tuesday, with strong to near gale force gusts possible for much of the waters. A new, long period northwesterly swell is anticipated by Wednesday of next week.

MTR WATCHES/WARNINGS/ADVISORIES
CA...Coastal Flood Advisory until 3 PM PST this afternoon for CAZ006- 506-508-529-530.

PZ...Small Craft Advisory from 3 PM Monday to 3 AM PST Tuesday for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

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

Small Craft Advisory until 3 AM PST Tuesday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

Small Craft Advisory until 9 PM PST this evening for Pigeon Pt to Pt Pinos 10-60 NM.