244
FXUS66 KMTR 040904
AFDMTR

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

...New SHORT TERM, LONG TERM...

.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...
(06Z TAFS)
Issued at 929 PM PDT Wed Sep 3 2025

Currently a mixed bag of IFR-VFR at the terminals with high clouds
streaming in from a low pressure system in the Eastern Pacific
Ocean. Moderate confidence in IFR/MVFR ceilings returning to most
of the terminals tonight with confidence lowering the farther
inland the terminal is. The pattern will change through the TAF
period as the longwave upper-level ridging shifts east from
approaching upper-level shortwave troughing. This will allow the
marine layer to deepen and penetrate farther inland tomorrow
night.

Vicinity of SFO...Currently VFR with westerly flow. Moderate
confidence on the return of a ceiling (likely on the cusp of
IFR/MVFR) to the terminal tonight. Westerly winds will prevail
through the TAF period.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently IFR with westerly flow at MRY and
MVFR with northwesterly flow at SNS. Brief VFR is expected tomorrow
afternoon with low stratus sticking close to the coast.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 929 PM PDT Wed Sep 3 2025

Moderate to fresh northwesterly breezes will prevail through
Saturday, slowly diminishing into Sunday. Locally strong gusts are
expected along the coastal jet regions through the week. Moderate
seas will prevail through the week.

&&

.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...Sarment
MARINE...Sarment

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