995
FXUS66 KMTR 111755
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1055 AM PDT Thu Sep 11 2025

...New AVIATION...

.KEY MESSAGES...
Issued at 1053 AM PDT Thu Sep 11 2025

 - Unsettled weather continues into Thursday

 - Drier and slightly warmer weather Friday and Saturday.

 - Unsettled weather may return to the Bay Area on Sunday.

&&

.UPDATE...
Issued at 834 AM PDT Thu Sep 11 2025

Satellite imagery shows extensive stratus coverage across the Bay
Area and Central Coast, expected to continue diminishing through
the morning hours. Main focus for today remains the chances for
showers in the North Bay through the afternoon and evening hours.
Chances remain slight but still pretty significant (15-30%
probability) across northern and central Sonoma and Napa Counties,
but accumulations should remain below a tenth of an inch.
Meanwhile, not expecting as much of a dip in temperatures on
Sunday with the models showing more of a zonal upper level flow
over central California, as opposed to a slightly more pronounced
troughing pattern which was depicted in model runs at this time
yesterday. No other changes to the forecast.

DialH

&&

.SHORT TERM...
Issued at 239 AM PDT Thu Sep 11 2025
(Today and tonight)

Quick recap - Afternoon/evening precip has diminished. There are a
few lingering echoes about 60 miles west over the ocean and near
Monterey Bay, but they`re fading fast. KMUX has been returned to
surveillance/clear air mode. Decent September rainfall amounts
recorded over the last 12-18 hours with a trace to nearly three
quarters of an inch. One notable rainfall total is San Jose, with
0.41 inches, which sets a new daily record.

Today and tonight: We`ve got one more day of precip chances
around the Bay Area. The reason? A double-barrel upper low
continues to spin over far NorCal, which is embedded in a
positively tilted upper level trough. Model guidance has been
rather persistent in keeping precip over the North Bay once again
this afternoon. Wednesday there were concerns of excessive
rainfall and thunderstorms, but that threat has shifted farther N
and E with better dynamics today. So is there a low chance for
thunderstorms again this afternoon? SPC brings the day one outlook
just to the Napa county line. Further analysis of CAMS reveals
some solid instability at the surface and just above the surface.
However, lapse rates aloft are meager at best from 700-500mb.
Additionally, point soundings show a weak cap/inversion around
650mb depending on your model of choice. Given the positive tilt
of a weakening trough don`t think that will be enough to tip the
scales toward thunder. Therefore, will keep precip mention to
showers over the North Bay. There could some build ups over the
Diablo and Gabilan ranges, but will not mention precip at this
time.

Otherwise, satellite fog product overnight shows a psuedo-marine
layer or more like strato-cu layer blanketing the Bay Area and
Central Coast. This layer will thin by late morning/early
afternoon, but given the lift nearby some afternoon clouds will
linger. Speaking of the satellite. One can still see a pronounced
heat signature from the Garnet Fire in the Sierra.

Any precip will diminish by tonight as the low/trough move
eastward and weakens further. In its wake subsidence develops
with a redeveloping marine layer around 2k feet.

&&

.LONG TERM...
Issued at 259 AM PDT Thu Sep 11 2025
(Friday through Wednesday)

Warmer and drier conditions develop on Friday and into Saturday
thanks to shortwave ridging that develops behind the departing
upper low. Night and morning marine layer clouds will return, but
compressed slightly. Temperatures return to the 70s and 80s with
interior Central Coast reaching the 90s.

A little bit of a roller coast temp-wise as temps dip slightly on
Sunday thanks to a passing front to the north. A few showers over
the northern coastal waters, but by the time they reach the North
Bay they fall apart.

Early next week longwave pattern continues to favor ridging over
the west with a low/trough Northern Rockies. A few of the
ensembles even show some weak offshore flow around Sept 16.

&&

.AVIATION...
(18Z TAFS)
Issued at 1053 AM PDT Thu Sep 11 2025

MVFR/VFR conditions across the region this morning expecting to lift
to VFR by this afternoon. Onshore winds will increase this afternoon
before diminishing after sunset and more so into Friday morning.
There is moderate to high confidence for MVFR ceilings to return
this evening, potentially lowering to IFR early Friday morning
across the Monterey Bay terminals. Ceilings are forecast to lift by
Friday afternoon to VFR with increasing onshore winds.

Vicinity of SFO...MVFR currently expected to return to VFR by early
afternoon with increasing onshore winds. Moderate to high confidence
for MVFR ceilings to return late this evening and persist through
the night. There is low confidence for sub-MVFR ceilings early
Friday morning before ceilings lift to VFR by Friday afternoon.
Onshore winds increase Friday afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...High confidence for VFR conditions to
return to the region by this afternoon and persist through late
afternoon or early evening. Then, high confidence for MVFR ceilings
to return and potentially lower to IFR early Friday morning.
Moderate confidence in timing of transition from MVFR to IFR
overnight tonight into Friday morning.

&&

.MARINE...
(Today through Tuesday)
Issued at 834 AM PDT Thu Sep 11 2025

Northwest winds increase beginning Thursday, becoming moderate to
fresh across the majority of the coastal waters. Localized strong
gusts are possible across the northern outer waters. Moderate to
rough seas develop Friday and persist into next week. Conditions
temporarily improve Saturday, as winds decrease and seas ease,
before another round of fresh to strong NW winds returns Sunday
into next week with the strongest winds located across the far
northern outer waters.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM to 9 PM PDT Friday for Mry Bay-
     Pigeon Pt to Pt Pinos 0-10 nm-SF Bay N of Bay Bridge.

     Small Craft Advisory from 9 PM this evening to 3 AM PDT Saturday
     for Pt Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory from 9 PM this evening to 9 AM PDT Friday
     for Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory from 3 PM Friday to 3 AM PDT Saturday for
     Pigeon Pt to Pt Pinos 10-60 NM-Pt Pinos to Pt Piedras
     Blancas 0-10 nm.

     Small Craft Advisory from 3 PM this afternoon to 3 AM PDT
     Saturday for Pt Arena to Pt Reyes 10-60 NM.

     Small Craft Advisory from 9 PM this evening to 3 AM PDT Friday
     for Pigeon Pt to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...RGass
MARINE...RGass

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