825
FXUS66 KMTR 030103
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
603 PM PDT Thu Oct 2 2025

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 120 PM PDT Thu Oct 2 2025

 - A slight chance for thunderstorms across the North Bay and
   Central Coast this afternoon and evening

 - Gusty onshore winds develop on Friday

 - Gradual warming trend begins this weekend with moderate offshore
   winds, especially in the higher elevations

&&

.SHORT TERM...
Issued at 120 PM PDT Thu Oct 2 2025
(This evening through tonight)

Showers remain confined to interior areas of San Bentio County as of
this writing. By this afternoon and evening there will be chances
for rain showers and isolated thunderstorms across the North Bay and
Central Coast with potential for rain showers elsewhere across the
Bay Area. This is as MUCAPE values reach up to 500 J/kg across the
Central Coast this afternoon and North Bay this evening and into
early Friday morning. The CAMs (Convection-Allowing Models) also
show indications of this.

Temperatures this afternoon are forecast to range from the mid 60s
near the coast to mid 70s across the warmer interior locations.
Tonight, temperatures will cool into the upper 40s across the
interior Central Coast and North Bay valleys with 50s elsewhere.

&&

.LONG TERM...
Issued at 1254 AM PDT Thu Oct 2 2025
(Friday through Wednesday)

The strong upper level low will move through the state through
Friday, with drier conditions across the region with the moisture
having moved off to our south. A strong pressure gradient over the
Bay Area and Central Coast will enhance northwesterly winds
across the region, with wind gusts reaching 25 to 35 mph at the
immediate coast, within the Salinas Valley, and through favored
gaps and passes across the region. Wind Advisories may prove
necessary if confidence in more widespread gusty winds increases.
Temperatures will be around the same as today for the Bay Area
with a drop expected in the Central Coast, with the southern
Monterey Bay region and northern Salinas Valley seeing highs in
the lower to middle 60s, while the warmest locations in southern
Monterey County reach highs in the lower to middle 70s.

The weekend features a warmup as the upper level low moves off
into the Great Basin. High temperatures range from the middle 70s
to the lower 80s in the inland valleys, the lower to middle 70s
close to the Bays, and the middle to upper 60s along the Pacific
coast. A surface high will develop in the northern Rockies,
setting up the possibility for moderate offshore flow Saturday
through Monday. These would usually raise fire weather concerns,
but the antecedent rainfall and the limited strength of the
offshore flow will mitigate the risk. The latest update of the
PGE-WRF model shows the SFO-WMC gradient reaching -2 to -6 mb,
which will cause some offshore flow, but keep it from being strong
enough to warrant any critical fire weather threats.

Beyond Monday, upper level troughing is expected to persist over
the western United States, at least through the middle part of
next week. CPC outlooks lean towards temperatures and
precipitation totals near the seasonal average into the middle
part of October.

&&

.AVIATION...
(00Z TAFS)
Issued at 603 PM PDT Thu Oct 2 2025

A 500 mb trough located 200 miles west of San Francisco continues
to move eastward. KMUX radar shows scattered showers developing
out ahead of the trough. The 00z evening Oakland upper air
sounding showed 1.02" precipitable water which is near the 90th
percentile in early October. A 700 mb thermal trough will align
with the aforementioned 500 mb thermal trough as it passes over
much of our forecast area tonight and Friday morning, resulting
in additional showers, including a few downpours. Drier weather
arrives from the northwest mainly Friday.

Expect VFR-MVFR with showers, including a few downpours tonight
and Friday morning. Recent global and mesoscale model forecasts
are not showing much precipitation, however the potential is there
for additional wet weather tonight and Friday morning. Lengthening
night-time hours i.e. lengthening potential for night-time radiative
cooling and a largely water vapor rich air mass will favor fog,
including dense fog development. Nocturnal radiative cooling to space
above cloud tops will favor strengthening instability/showers, which
may include isolated lightning. Will closely monitor radar and
satellite through the evening, amending TAFs as needed.

Vicinity of SFO...VFR. Shower activity west of the SF Peninsula
will be monitored for potential additional development due to an
aligning and eventual arrival of a 700 mb to 500 mb thermal trough.
Will amend SFO TAF as needed based on any changes seen e.g. on
radar, satellite and upstream and nearby surface observations.

The presently water vapor rich air mass lingering tonight to the
time of max nocturnal cooling nearest daybreak Friday may present
forecast difficulties with respect to areal coverage of low clouds
and/or fog. Drier conditions arrive Friday improving the chance of
VFR during the day.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR, however post sunset cooling and the
arrival of a 700 mb to 500 mb thermal trough tonight will likely
bring a combination of lowering cloud ceilings and surface
visibilities /IFR/ in addition to temporary mixing winds associated
with passing showers and/or downpours. Similarly to the Bay Area,
the presently water vapor rich air mass lingering tonight to the
time of max nocturnal cooling nearest daybreak Friday may present
forecast difficulties with respect to areal coverage of low clouds
and/or fog. Drier conditions arrive Friday improving the chance of
VFR during the day.

&&

.MARINE...
(Tonight through next Wednesday)
Issued at 519 PM PDT Thu Oct 2 2025

Sparse shower activity lingers in the outer waters into the
night. Winds increase in the late night and through Friday,
causing widespread hazardous conditions for small craft. These
winds will support rough wind waves up to 10 feet through the
weekend. Winds and seas ease into the next work week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM Friday to 3 AM PDT Saturday for
     Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes
     10-60 NM.

     Small Craft Advisory from 3 AM Friday to 3 AM PDT Saturday for
     Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-
     Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon
     Pt 0-10 nm.

&&

$$

SHORT TERM...RGass
LONG TERM....DialH
AVIATION...Canepa
MARINE...Murdock

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