220
FXUS66 KMTR 032330
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
430 PM PDT Wed Sep 3 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1228 PM PDT Wed Sep 3 2025

 - Gradual cooling trend through the remainder of the week.

&&

.SHORT TERM...
Issued at 1228 PM PDT Wed Sep 3 2025
(This evening through Thursday)

Zonal flow continues through the remainder of Wednesday before
giving way to a weak upper level trough early Thursday morning.
Temperatures will continue their subtle downwards trend Wednesday to
Thursday with highs dropping another 2-4 degrees across the region.
High temperatures on Thursday will generally be in the mid 70s to
80s across the interior and 60s to low 70s along the coastline. The
exception will be for our typical hotspots (far interior North Bay,
Byron, and interior Central Coast) where highs will continue to be
in the upper 80s to mid 90s. Winds will stay diurnally breezy across
the region with gusts to around 25 to 30 mph across the Salinas
Valley and Altamont Pass region.

The marine layer is expected to remain between 1000-1500 ft tonight
into early Thursday morning. This is expected to bring drizzle and
patchy fog along the coastline. The marine layer is set to deepen to
around 1800-2000 ft by Thursday night as zonal flow gives way to
weak upper level troughing. This will result in morning coastal
drizzle being a daily occurrence into this weekend.

&&

.LONG TERM...
Issued at 1228 PM PDT Wed Sep 3 2025
(Thursday night through next Tuesday)

Upper level troughing will deepen over the West Coast Friday into
next week. Temperatures continue to cool Friday into the 70s to mid
80s across the interior. Temperatures will cool another 1-3 degrees
Saturday (70s to low 80s) across the interior and remain relatively
stable in that range through the remainder of the forecast period.
As mentioned in the short term discussion, upper level troughing
will allow the marine layer to deepen, bringing daily coastal
drizzle and allowing for improved overnight humidity recoveries.
This will slightly reduce fire weather concerns across the interior
Bay Area with ERC values (measure of how much energy is available
for a fire) to drop and fuel moistures to rise slightly. As the
upper level trough deepens next week, the GFS shows potential for
rain to develop across northern CA. This is expected to remain well
north of our CWA with only 2 out of 30 GFS ensemble members showing
more than a tenth of an inch at STS next week (4 out of 30 show a
trace at STS, 24 out of 30 show nothing at STS). The CPC 6-10 day
outlook shows near to below normal temperatures and a chance for
above normal precipitation continuing through September 13th.

&&

.AVIATION...
(00Z TAFS)
Issued at 429 PM PDT Wed Sep 3 2025

Currently VFR at all terminals with the exception of HAF. Moderate
to high confidence on the return of sub-VFR ceilings to bayshore and
coastal terminals - lower confidence inland. High confidence in
widespread VFR by tomorrow afternoon.

Vicinity of SFO...Currently VFR with northwesterly 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 VFR with westerly flow at MRY and
VFR with northwesterly flow at SNS. Moderate to high confidence on
the return of IFR ceilings to the terminals tonight. Onshore winds
will prevail through the TAF period.

&&

.MARINE...
(Tonight through next Monday)
Issued at 429 PM PDT Wed Sep 3 2025

Moderate to fresh northwesterly breezes will prevail through
Saturday. Wind gusts become fresh to strong by Thursday through
Saturday along the favored coastal jet regions, these conditions
be hazardous to small craft. Moderate seas will prevail through
Friday and become low for the upcoming weekend. Winds decrease
some on Sunday morning and become gentle to moderate for the rest
of the weekend.

&&

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

&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...Sarment
MARINE...RGass

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