539
FXUS66 KMTR 070016
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
416 PM PST Sat Dec 6 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1200 PM PST Sat Dec 6 2025

 - Benign conditions through the next seven days with no
   precipitation expected and a gradual warming trend

 - Impacts from Tule Fog continue in the North Bay and interior
   East Bay valleys, with potential for expansion across the rest
   of the Bay Area tonight

 - Next chance for rain towards the middle of the month

&&

.SHORT TERM...
Issued at 1200 PM PST Sat Dec 6 2025
(This evening through Sunday)

The current satellite image shows dissipating stratus across the
Santa Clara Valley and the San Francisco Bay Shoreline, while the
City and the valleys of the North Bay and interior East Bay remain
socked in the spillover from the Tule Fog across the Central Valley.
Towards the western parts of Sonoma and Marin counties, the Tule Fog
spillover merges with marine layer stratus. The trend of the last
couple of days has been the models struggling to accurately reflect
the evolution of the Tule Fog in the North and East bay valleys.
Model output shows the stratus deck beginning to dissipate over the
North Bay valleys now, but that does not appear to be happening. I
have tamped down the highs for today and tomorrow across the Bay
Area in response to the model`s struggles. The current forecast has
today`s highs in the upper 50s across the Bay Area valleys, with
central and eastern Contra Costa County and far eastern Alameda
County seeing highs in the lower to middle 50s. This does assume
that the stratus does eventually mix out this afternoon, and if
the stratus lingers through the day, the North and East bay
valleys might not get out of the 40s. Tomorrow`s forecast
currently has the highs warming by a couple of degrees, within a
couple degrees of 60 for most of the area, but this is highly
dependent on how the Tule Fog evolves tonight into Sunday morning,
and could also need to be dropped if the stratus sticks around
long enough tomorrow.

Meanwhile, over in the Central Coast the skies are clear, have
remained generally clear this morning, and will remain clear during
the afternoon and evening hours. Model output is showing some
possibility for stratus to develop in the Monterey Bay region and
northern Salinas Valley tonight. While is some reason to second-
guess the model output, for the reasons stated above, those reasons
lean towards more stratus being present than the current forecast.
However, any influence from the Tule Fog will be limited to the far
eastern reaches of San Benito and southern Monterey Counties, where
the Gabilan Range abuts the Central Valley. Highs in the Central
Coast reach the middle to upper 60s in the inland valleys, to the
lower to middle 60s closer to Monterey Bay, perhaps into the lower
70s in some of the sheltered valleys within the Santa Lucia and
Gabilan ranges.

&&

.LONG TERM...
Issued at 1200 PM PST Sat Dec 6 2025
(Sunday night through next Friday)

Ridging will dominate the weather patterns through the rest of the 7-
day outlook, enabling a gradual warming trend across the region. The
highs will peak around the later part of the upcoming work week with
highs in the inland valleys reaching the middle 60s to middle 70s,
around 8 to 13 degrees above the seasonal average. As with the short
term forecast, the biggest source of uncertainty will be how the
Tule Fog develops every night and morning, impacting the
temperatures across the North and East Bay valleys. The
deterministic forecast has the East Bay interior valleys remaining
in the lower to middle 60s, but depending on how the Tule Fog
evolves the temperatures could easily vary by around 10 degrees on
either side of the current forecast.

A couple of storm systems will approach the West Coast during the 7-
day outlook, but the ridging pattern will deflect the brunt of the
storms to the Pacific Northwest and leave us with a chance of
drizzle in the coastal waters while land areas remain dry. Longer
range model guidance suggests a possible change in the weather
pattern towards the middle of the month. Ensemble model cluster
analysis continues to show some of the model members (somewhere
around 30-40% of the ensemble members) depicting a breakdown of the
ridge. however, most of the ensemble members and the ensemble means
point to the ridge persisting over the western United States, or
flattening out into a zonal flow pattern. Uncertainty remains rather
high in this part of the forecast and we will keep an eye on what
the trend from later model runs turns out to be.

&&

.AVIATION...
(00Z TAFS)
Issued at 416 PM PST Sat Dec 6 2025

Low clouds and fog continue in the North Bay and interior East Bay.
Expect cloud cover in these areas to lower further into the night
and the fog to become thicker. The SF Bay terminals as well as SJC
see CIGs arrive overnight with some slight reductions in
visibilities. Winds stay mostly light to moderate through the
morning, with wind directions determined by more localized affects.
Cloud cover and fog will be slow to erode into Sunday, but
conditions look to improve into the afternoon. However, the North
and East Bay will continue to struggle with low clouds and fog,
causing some doubt for clearing at STS and LVK, while APC doesn`t
look to clear for Sunday afternoon. While over sites see less
chances for low clouds and fog into that afternoon, pockets of haze
will affect much of the region.

Vicinity of SFO...VFR lasts into early Sunday morning. Moderate
northerly winds become lighter and more westerly into the night
before becoming more variable into early Sunday morning as IFR CIGs
fill over the terminal. CIGs scatter in the mid morning, and
moderate northwest winds arrive that afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the TAF period. Winds stay
light for MRY through the TAF period, while SNS sees moderate
northwest winds become light into the early night. Expect winds to
turn southeast overnight. Northwest winds return Sunday afternoon
with the potential for haze along the coast.

&&

.MARINE...
(Tonight through next Friday)
Issued at 416 PM PST Sat Dec 6 2025

Strong to near gale force gusts will be possible through the end
of the weekend, with breezy northwest winds lasting into the
middle of next work week. Moderate seas with wave heights 6 to 8
feet across the outer waters this weekend. 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 Sunday for CAZ006-506-508-
     529-530.

PZ...Small Craft Advisory from 3 PM to 9 PM PST Sunday for Pigeon Pt
     to Pt Pinos 0-10 nm.

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

     Small Craft Advisory from 9 AM Sunday to 3 AM PST Monday for Pt
     Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory until 3 AM PST Sunday for Pigeon Pt to Pt
     Pinos 10-60 NM.

     Small Craft Advisory from 9 AM to 9 PM PST Sunday for Pigeon Pt
     to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Murdock
MARINE...Murdock

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