219
FXUS66 KMTR 041743
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
943 AM PST Thu Dec 4 2025

...New AVIATION...

.KEY MESSAGES...
Updated at 831 AM PST Thu Dec 4 2025

 - Cold Weather Advisory for southern Monterey and San Benito
   counties midnight to 8 AM Friday

 - Benign conditions and with only a few showers over the coastal
   waters expected through the next seven days

 - Slight warming trend begins Friday through the weekend

&&

.UPDATE...
Issued at 831 AM PST Thu Dec 4 2025

Satellite imagery shows the Tule Fog extending into the interior
East Bay and parts of the North Bay valleys, with a largely
separate band of stratus impacting the southern Salinas Valley.
The Cold Weather Advisory for the North Bay valleys was allowed
to expire at 8 AM, but chilly conditions could continue in some
places for another couple of hours. The Cold Weather Advisory in
the interior Central Coast continues through 8 AM Friday. This may
need to be reevaluated if cold conditions persist longer than the
current forecast. No changes to the forecast at this time.

DialH

&&

.SHORT TERM...
Issued at 327 AM PST Thu Dec 4 2025
(Today and tonight)

Longwave pattern over the EPac through Plains is complicated with:
two upper lows (one west of Baja and the other east of Hawaii), a
large area of high pressure off the CA coast extending into the
PacNW, and a shortwave trough sweeping through the 4-corners.
Despite the complexity, pretty quiet weather across the Bay Area
and Central Coast with minor to moderate impacts. Satellite
imagery continues to show widespread mid-high level clouds
streaming the northern periphery of the ridge and spilling over
the Bay Area. The high clouds initially limited radiational
cooling, but gradual thinning over the last few hours had led to a
steady drop in temperatures. A Cold Weather Advisory has been
issued for the North Bay Valleys, and Interior Central Coast (S
Monterey/San Benito) through 8 AM for cold temps 33 to 36 degrees.
Even seeing a few 20s across interior San Benito. This is the
first Cold Weather Advisory of the season. Areas outside of the
advisory are chilly and in the upper 30s and 40s - low 50s coast.
Winds were stronger yesterday, but still seeing some gusty winds
in the hills of the North Bay with Mt St Helena still shows gusts
35-45 mph. The larger offshore gradient is still on track to relax
during the afternoon leading to weakening winds over the North Bay
Mts. Despite the chilly start in some locales, today`s temps will
warm into the 50s and 60s or seasonal averages . One last item in
the near term is pesky Tule Fog developing in the Central Valley
again. Fog was initially slow to get going (likely due to some of
the high clouds), but now it`s in full force in the West Delta
and interior East Bay Valleys. Clouds and locally dense fog will
be the main impacts.

For tonight, slight warm up, but still chilly across the interior.
Coldest temperature will be over the interior Central Coast and
therefore have extended the Cold Weather Advisory through Friday 8
AM for that location with lows in the 33 to 36 degree range.

&&

.LONG TERM...
Issued at 400 AM PST Thu Dec 4 2025
(Friday through Wednesday)

The ridge to our west shifts east Thursday night into Friday. As
such, a gradual warming of the airmass is expected. Still a
chilly start to the day Friday, but afternoon temperatures will
rebound and be up 3-5 degrees from Thursday. Additional warming is
expected over the weekend. One other thing we`ll be keeping an
eye on heading into the weekend will be precip chances. A few weak
systems pass to the north and get buffeted by the ridge overhead.
As such, precip chances remain highest north of the region. The
exception will be tail ends of decaying cold fronts bringing
precip chances to the coastal waters Friday and Saturday.

The ridge does flatten, but then remains parked off the SoCal
coast through the middle of next week. That means high and dry
conditions for the Bay Area and Central Coast. Interior Central
Coast may even hit the mid 70s by next Wednesday.

Longer range ensemble guidance better precip return by the middle
of the month.

&&

.AVIATION...
(18Z TAFS)
Issued at 942 AM PST Thu Dec 4 2025

VFR trough the TAF period, with the exception of KLVK which is
currently IFR this morning and forecast to improve to VFR by early
afternoon. Light to moderate offshore winds prevail this morning
before becoming north-northwesterly this afternoon across the Bay
Area and Monterey Bay terminals. Friday morning, there is a low
probability (less than 25% chance) of LIFR ceilings and/or
visibilities for KSTS. Winds diminish overnight with greater
probability of onshore winds by Friday afternoon.

Vicinity of SFO...VFR through the TAF period. Offshore winds
prevail this morning and are expected to become north-
northwesterly by mid- to-late afternoon. Winds diminish overnight
with greater probability of onshore winds by Friday afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the TAF period. Light to
southerly winds prevail this morning and are forecast to become
onshore by early-to-mid afternoon. Winds diminish overnight and
become southerly early Friday morning.

&&

.MARINE...
(Today through Tuesday)
Issued at 831 AM PST Thu Dec 4 2025

Winds are diminishing and seas are subsiding. Expect mostly calm
conditions into the night before breezy to gusty northwest winds
return with rebuilding seas up to 8 feet by Friday. Winds stay
breezy into the next work week, but seas abate in the early week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 3 PM PST Sunday for CAZ006-506-508-
     529-530.

     Cold Weather Advisory until 8 AM PST Friday for CAZ516-518.

PZ...Small Craft Advisory from 9 AM Friday to 3 AM PST Saturday for
     Pt Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory from 9 PM this evening to 3 AM PST Saturday
     for Pt Arena to Pt Reyes 10-60 NM.

     Small Craft Advisory from 3 AM Friday to 3 AM PST Saturday for
     Pigeon Pt to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...RGass
MARINE...RGass

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