562
FXUS66 KMTR 041125
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
425 AM PDT Thu Sep 4 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1252 AM PDT Thu Sep 4 2025

 - Quiet weather into the weekend with breezy afternoon onshore winds
   each day.

 - Cooling trend this weekend into next week as upper level system
   approaches West Coast.

 - Unseasonably cool and moist airmass appears likely next week.

&&

.SHORT TERM...
Issued at 1252 AM PDT Thu Sep 4 2025
(Today and tonight)

Mostly rinse and repeat with slightly cooler temperatures today in
the North Bay and SF Bay Area due to more robust Pacific moisture
under a deep marine layer. Mostly clear this afternoon with
breezy onshore gap winds in favored locations such as the Golden
Gate, Altamont Pass, and the Salinas Valley. Highs generally in
the 70s to lower 80s across the Bay Area, 60s along the coast.

&&

.LONG TERM...
Issued at 1252 AM PDT Thu Sep 4 2025
(Friday through Wednesday)

Medium range guidance is hinting a bit of a pattern shift through
this weekend into next week. An active upper level pattern in the
NEPac shifts southward with several weak disturbances affecting
the West Coast. This is anticipated to bring in a much more
"winter-like" (for us) airmass with deep moisture and much cooler
temperatures aloft. Confidence is reinforced by ensemble cluster
analysis representing a fairly even spread across very similar
solutions. Of note with this airmass; guidance is advertising 850
mb temps of about 12.5 C and PWAT of just above 1.0" by early to
mid next week, which falls around the 25th and 90th percentiles
for this time of year, respectively. What will likely be missing
with these systems is a consistent source of forcing. Thus, we
aren`t expecting "rain" out of this...sticking with the "heavy
drizzle" terminology for now. Stay up to date for updates
regarding this potential pattern change.

&&

.AVIATION...
(12Z TAFS)
Issued at 412 AM PDT Thu Sep 4 2025

LIFR-MVFR ceilings are blanketing all TAF sites this morning. The
typical pattern of clearing in the late morning is expected for
all but the most coastal sites (HAF, MRY) where clouds may linger
through the day. The marine layer will likely deepen over the
next 24 hours as a trough approaches the coast. This will keep the
cooling trend going with extensive low cloud coverage and periods
of mist in the morning at the typical terminals.

Vicinity of SFO...It took a while, but clouds have finally filled
in the entire bay with ceilings in the IFR-MVFR range. With
boundary layer averaged winds out of the SW, there is high
confidence in clearing around 20-21Z. Surface winds will increase
to a moderate breeze this afternoon before ceilings return
sometime this evening, but the exact timing is uncertain at this
time due to significant model spread.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR ceilings are expected through the
morning with a good chance for the visibility to periodically drop
below 2 miles at both MRY and SNS this morning. There will be some
clearing in the late morning, but some guidance indicates MRY will
keep a ceiling all day. The TAF leans optimistic for now, but
it`s essentially a coin-flip.

&&

.MARINE...
(Today through Tuesday)
Issued at 412 AM PDT Thu Sep 4 2025

Moderate NW winds and moderate seas will prevail through Friday
with locally strong gusts in the vicinity of Point Sur. Winds will
diminish to a gentle breeze over the weekend, allowing seas to
subside below 5 feet by Sunday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Friday
     for Pt Pinos to Pt Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...Flynn
MARINE...Flynn

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