Marine Weather and Tide Forecast for Sunnyvale, CA

SHORT TERM
Issued at 1234 PM PST Sun Nov 9 2025 (This evening through Monday)

Another warm day is in store for the region as mostly sunny skies prevail (just a few passing high clouds). As such, temperatures are forecast to warm into the the low-to-mid 80s across the interior with the warmest spots across the interior Central Coast approaching 90 degrees F. Near the coast and in the coastal adjacent valleys, expecting low 70s to low 80s. A southerly surge is moving northward along the Big Sur coastline, yet should mostly impact locations along the immediate coast across this region.

Tonight, expecting low clouds and/or fog near the coast as a shallow marine layer deepens slightly to around 500 feet. However, weak offshore winds prevail across the higher elevations will keep drier conditions in those areas.

Monday is forecast to be our warmest day of the week (especially inland). Any low stratus and/or fog that does develop will quickly retreat to the coast by late morning or early afternoon. However, onshore flow is likely to keep coastal temperatures a few degrees lower and inland temperatures a few degrees warmer than what is forecast for this afternoon.

LONG TERM
Issued at 1234 PM PST Sun Nov 9 2025 (Monday night through next Saturday)

On Tuesday, the ridge begins to shift eastward which will start a cooling trend as onshore winds become more widespread (even in the higher elevations). However, afternoon temperatures will remain 5-15 degrees above seasonal averages.

By Wednesday, high level clouds will increase across the region ahead of an approaching weather system bringing temperatures closer to seasonal averages. Rain looks to be greatest from Wednesday night through early Thursday morning as an atmospheric river takes aim on the Bay Area and Central Coast. The coastal ranges and inland hills/mountains in the Bay Area and North Bay have the greatest potential (60%+) of seeing greater than 2.00" from 4 AM Wednesday through 4 AM Friday. The North Bay Valleys and San Francisco could see up to 1.50" with generally less than or around 1.00" for the the remainder of the region. Given this is an atmospheric river, the rain shadowed valleys may receive much less with respect to rainfall. Southerly winds will increase ahead of the cold front, but exact strength of these winds still remain in question. However, expect the strongest winds to be along the coastline and in the higher elevations across the region. There is also a less than 15% probability of thunderstorms Wednesday night and into Thursday as the main band of convection moves across the region. Once we get in the range of the higher resolution forecast models, we will be able to nail down the details (wind, rainfall amounts, thunderstorm potential, etc).

From the previous forecaster: "After the main rain band moves out late Thursday, an extended period of lighter rain, possibly showery in nature, lingers Friday into the upcoming weekend. The axis of the upper level trough crosses into the state early on Friday, promoting unstable conditions resulting in the possible development of convectively driven showers. There is also a chance that a cut-off low could develop off the coast of southern California, which could enhance the rain potential across the Central Coast. That said, with the moisture tap moving to the south and into southern California and Baja California, there will be less moisture for the showers to tap into, and the rain totals for this part of the system trend lower than those on Wednesday and Thursday. The precipitation chances start out around 40-60% on Friday morning and steadily decrease into Saturday.

Beyond the 7 day outlook, ensemble model means are suggesting another trough may develop somewhere around the Day 8-9 (the 16th and 17th) timeframe, bringing another chance of rain to the region.
This far out, attempting to tease out any further details is a fool's errand."

AVIATION
(00Z TAFS)
Issued at 340 PM PST Sun Nov 9 2025

VFR conditions at all terminals through early tonight. The challenge for the next 24 hours will be the surge sneaking up the coast. Not expecting impacts to the big three, but we'll need to watch HAF,MRY,SNS closely. Highest conf now are low cigs impacting HAF, SNS.

Vicinity of SFO...VFR. Light winds now getting a onshore push this evening. Light winds tonight then another onshore push Monday.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...southerly surge sneaking up the coast looks to keep VFR through early tonight before low cigs move into SNS first then MRY overnight.

MARINE
(Tonight through next Friday)
Issued at 340 PM PST Sun Nov 9 2025

A southerly surge moving northward will bring a shift in winds and patchy dense fog south of the Golden Gate, especially near shore, through tonight. Areas of north of the Golden Gate will remain light to moderate winds and out of the north. Southerly surge ends Monday with northerly flow all waters. Unsettled weather returns midweek with increasing southerly winds. These winds, combined with a building NW swell, will generate rough seas across the waters. Winds are expected to decrease Friday, but the high swell continues to build with significant wave heights reaching up to 15 feet before diminishing through the weekend.

MTR WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...None.