468
FXUS66 KMTR 120058
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
558 PM PDT Fri Jul 11 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1242 PM PDT Fri Jul 11 2025

 - Moderate HeatRisk across portions of interior Bay Area today

 - Cool trend starts this weekend

 - Gusty onshore winds through gaps in terrain each afternoon may
   cause any grass fires to run

&&

.SHORT TERM...
Issued at 1242 PM PDT Fri Jul 11 2025
(This evening through Saturday)

It is really hard to choose any other ways to describe our weather
than Goldilocks weather. It is simply just right, as far as
summer weather goes. The afternoon satellite imagery shows a pile
of low clouds along the immediate coast, with a nice eddy north of
Point Reyes. There`s also a low cloud finger trying to thread the
needle of the golden gate, but eroding quickly past Angel Island
due to warm air. In addition to the low clouds at the coast smoke
from the Nor Cal fires is drifting overhead around the Bay Area.
Looking at fire.airnow.gov, it does not look like the smoke is
reaching the ground, but rather the sun combining with pollutants
at the surface are causing moderate air quality in populated
areas. Winds are forecast to become more onshore this afternoon,
all the way through 850 hPa, which should shove the smoke to the
east, but will also bring the low clouds in.

Looking at box and whisker plots around the area, temps tomorrow
start to show a cooling trend with a fairly tight spread on the
box. This gives some confidence that models are catching on to the
pattern well. The caveat is that temps aloft do stay warm,
sitting on top of the onshore marine push. As such, Max T for
Saturday above 500 feet was made by blending the official forecast
with NBM 75th percentile. This brought temps up a few degrees
over the previous forecast.

Beyond this, the pattern remains quiet and, well, Goldilocks
weather like. Just right.

&&

.LONG TERM...
Issued at 1242 PM PDT Fri Jul 11 2025
(Saturday night through next Thursday)

Rinse. Lather. Repeat. Summertime in the Bay Area and along the
central coast can be repetitive and the weekend through next week
looks to be that. An upper ridge will remain near our region, but
a quasi-permenant shortwave trough looks to be embedded in the
ridge right over the Bay Area and Central Coast. This means that
we`ll sit, surrounded by heat, with onshore flow and seasonable to
below seasonable temperatures. If you have friends or family that
live in the other parts of California, expect a text from them
soon asking if they can come stay with you for a bit.

&&

.AVIATION...
(00Z TAFS)
Issued at 558 PM PDT Fri Jul 11 2025

Stratus and fog continue to pull away from the coastal North Bay
where the marine layer depth is shallower at approximately a few
hundred feet. Wildfire smoke from northernmost California
continues to enter the mix, smoke may add to reducing surface
visibilities in hazy or foggy conditions in the Bay Area tonight
and Saturday morning. Southward from Point Reyes along the coast
the marine layer depth is somewhat greater at approximately 1200
feet and satellite imagery shows stratus and fog coverage is
continuous. Where there is coastal stratus and fog conditions are
mainly IFR. Onshore winds will usher stratus and fog /IFR-LIFR/
inland tonight and Saturday morning. The ACV-SFO northerly
pressure gradient is 4.8 mb juxtaposed to a SMX-SFO 3.0 mb and
SBA-SFO 2.2 mb southerly pressure gradient setting up a surface
wind pattern favoring weak and stationary surface troughing over
the coastal waters. The onshore component SFO-SAC 2.9 mb supports
onshore winds. A few patches of light coastal drizzle are possible
tonight and Saturday morning. Farthest inland and across the
southern half of the forecast areas is where VFR will have the
best chances to continue.

Stratus, fog, wildfire smoke, patchy light drizzle /IFR-LIFR/
improving to MVFR-VFR by late morning and/or afternoon, while
MVFR-VFR continues farthest inland. Coastal stratus, fog, wildfire
smoke, patchy light drizzle combination returns Saturday night and
Sunday morning.

Vicinity of SFO...Moderate to high confidence VFR continues through
the evening and tonight. West winds are mainly focused through the
Golden Gate to Angel Island, limiting wind flow through the San Bruno
Gap to SFO currently. Will continue to monitor wind flow through the
Golden Gate north of the Bay Bridge and across the San Francisco
Peninsula in general as any shift in the surface pressure gradient
and winds may favor a stronger west wind at SFO, however not seeing
that set up currently since a nearly stationary surface trough is
setting up over the nearby coastal waters. Otherwise the marine
layer depth ~ 1200 feet in the vicinity of SFO does support a gusty
west wind, but as mentioned not quite as robust in strength at SFO
as compared to north of the Bay Bridge and to Oakland Airport.

SFO Bridge Approach...Similar to SFO. Otherwise incoming wildfire
smoke may restrict slant range visibility especially at sunset and
sunrise.

Monterey Bay Terminals...A different kind of complex wind flow and
transport of stratus and fog /IFR/ currently is going on around the
Monterey Peninsula. A southwest wind continues at KMRY with the
marine layer depth ~ 1200 feet supports downsloping and drying
which should keep VFR going a little while longer. This wind flow
is likely in response to the aforementioned SMX-SFO and SBA-SFO
pressure gradients favoring a southerly wind component. Meanwhile
the surface wind is W-NW at KSNS favors the transport of stratus
and fog /IFR/ there this evening, ceiling and visibility lowering
to LIFR tonight and Saturday morning. Likewise at KMRY conditions
will eventually lower to LIFR tonight and Saturday morning. Patchy
light drizzle possible tonight and Saturday morning, may amend to
include in the TAFs later in the evening. Winds mainly onshore 5
to 10 knots tonight and Saturday morning. Conditions improving to
MVFR-VFR by late Saturday morning and afternoon. HREF output shows
stratus /MVFR- IFR/ nearby just after the 00z TAF cycle for Saturday
evening and night.

&&

.MARINE...
(Tonight through next Thursday)
Issued at 507 PM PDT Fri Jul 11 2025

Strong northerly breezes with gale force gusts and rough to very
rough seas will continue for the far northwestern portion of the
northern outer waters through Saturday. Gusty afternoon and early
evening onshore winds will continue mainly north of the Bay Bridge
each day through the weekend. Elsewhere, a gentle to moderate
breeze with moderate to rough seas will prevail.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 PM PDT this evening for SF Bay N of
     Bay Bridge.

     Small Craft Advisory until 3 PM PDT Saturday for Pt Arena to Pt
     Reyes 10-60 NM.

&&

$$

SHORT TERM...BFG
LONG TERM....BFG
AVIATION...Canepa
MARINE...Canepa

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