126
FXUS66 KMTR 270412
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
912 PM PDT Sat Sep 26 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1204 PM PDT Sat Sep 26 2026

 - Cooler conditions through Sunday

 - Warmer temperatures return Tuesday through the next week

&&

.SHORT TERM...
Issued at 1204 PM PDT Sat Sep 26 2026
(This evening through Sunday night)

The stratus deck has mixed out to the immediate coast of Marin
County and the Ocean Beach side of San Francisco and lurking near or
just off the coast of San Mateo County. High clouds continue to flow
over the North Bay and will continue to do so through the day, as
the stratus deck returns to many of the coastal valleys this evening
into the overnight period.

A developing trough with an axis around 600 miles west of Cape
Mendocino is approaching the West Coast, digging deeper into the
upper level flow as it does so and eventually dropping deep enough
to cross into the California coast, where it should further develop
into a cut-off low somewhere around the North Coast and the northern
half of the Central Valley through the latter portion of Sunday. The
influence of the cut-off low will bring cooler and more moist
conditions to the region. High temperatures will range around 5 to
15 degrees below seasonal averages for today and Sunday, with highs
in the inland valleys reaching the middle 70s to lower 80s today and
the 70s on Sunday. High temperatures in the warmest portions of
southern Monterey County will range from the middle 80s to lower 90s
today, and the upper 70s to middle 80s on Sunday. Meanwhile, the
Bayshore regions should expect highs in the upper 60s to upper 70s
on Saturday and the middle 60s to middle 70s on Sunday, while the
Pacific coast remains relatively cool with highs in the upper 50s to
middle 60s on both days.

As the cut-off low moves across the state through the weekend,
cooler temperatures and some incoming moisture should result in a
wetter mid-layer, around the 300-500 mb layer. Exceedingly dry lower
layers should cause the evaporation of most precipitation that may
result, but can`t rule out a few sprinkles overnight for the coastal
regions and the highest peaks.

&&

.LONG TERM...
Issued at 1204 PM PDT Sat Sep 26 2026
(Monday through next Friday)

Ridging should return to the region on Monday as the low moves into
the Mojave Desert, setting up pushes of higher elevation offshore
flow each morning from Monday to Wednesday, chiefly across the North
and East Bay interior mountains. The strongest push looks to be on
Tuesday morning with wind gusts of 25 to 35 mph possible in the
interior mountains of the North Bay. The potential for wind gusts
above 35 mph is greatest at the ridgeline of the Vaca Mountains
along the eastern border of Napa County.

Otherwise, the arrival of the ridge should allow for temperatures to
warm for the next week. By Tuesday, highs should reach the middle
80s to middle 90s in the inland valleys, the middle 70s to the
middle 80s for the Bayshore regions, and the 60s to the lower 70s
for the Pacific coast. These highs should basically remain stable
through the rest of the 7-day outlook as ensemble model means and
cluster guidance suggest that the ridging pattern should stick
around in some shape or form into the upcoming weekend and possibly
beyond.

&&

.AVIATION...
(06Z TAFS)
Issued at 848 PM PDT Sat Sep 26 2026

A mix of VFR and MVFR as the marine layer begins to gradually
strengthen out ahead of an advancing upper trough. Moderate
confidence that a majority of the terminals see MVFR/IFR ceilings,
with plenty of uncertainty in the extent and exact timing for the
North Bay and Bay Area sites.

Vicinity of SFO...The KOAK sounding showed a weak marine layer
around 1000ft, but should continue to gradually strengthen and
organize. There is dry air aloft mixing to the surface which
provides uncertainty on the extent and exact timing. Went on the
more pessimistic side of most guidance, bringing MVFR ceilings in
the in the pre-dawn hours, but may not happen until after sunrise
Sunday. Expect some coastal drizzle where stratus develops. Once
the stratus lifts by late morning Sunday, VFR for a majority of
the forecast period thereafter.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Stratus ceilings will hover around
MVFR/IFR until mid/late Sunday morning with possible drizzle,
with VFR for the remainder of the afternoon and early evening.
MVFR ceilings expected to return around sunset Sunday evening.


&&

.MARINE...
(Tonight through next Friday)
Issued at 848 PM PDT Sat Sep 26 2026

Moderate north winds will persist through the weekend, becoming
strong and gusty as high pressure builds over the the EPAC which
will result in a tightening pressure gradient over the coastal
waters, with the strongest gusts occuring along the outer coastal
waters from Monterey Bay south to Big Sur. Tropical activity will
produce long period southerly swell by the middle of the week.

&&

.FIRE WEATHER...
Issued at 420 AM PDT Sat Sep 26 2026

Our diffuse cold front continues to slowly move southward through
Southern California. In its wake, some areas have benefited from
the cooler and slightly more "moist" conditions this morning. The
exception, however, is across the higher terrain of the Santa
Cruz Mountains as well as the Santa Lucia and Diablo Ranges where
RH recovery remains poor (20-40%). Afternoon humidity will remain
under 40%, largely for areas away from the coast. A push of
onshore flow is expected later this evening into Sunday morning
resulting in the marine layer deepening to around 2,000 feet ahead
of an upper trough. This moisture push should diminish the areal
coverage of poor RH recovery Sunday and Monday morning. A few
sprinkles cannot be ruled out along the highest peaks associated
with this upper low Sunday AM. Dry and modest offshore breezes
will be a possibility Tuesday and into Wednesday, with the
potential for wind gusts above 35 mph being greatest across the
higher terrain of the North Bay in the wake of this upper low.
Farther south across the Central Coast, the primary impact from
this low will be a return to widespread poor RH recovery with some
locales across the Santa Lucia Range struggling to see max RH
above 30% Wednesday morning.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM Sunday to 3 AM PDT Monday for Mry
     Bay-Pigeon Pt to Pt Pinos 0-10 nm.

     Small Craft Advisory until 9 PM PDT Monday for Pt Pinos to Pt
     Piedras Blancas 0-10 nm.

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

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

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...JM
MARINE...JM

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