FXUS66 KMTR 241206
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
506 AM PDT Thu Sep 24 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1103 AM PDT Wed Sep 23 2026

 - Warming trend continues into Thursday bringing pockets of
   moderate HeatRisk across parts of the Bay Area and north 
   Central Coast.

 - Cooler conditions arrive Friday into the weekend.

 - Near seasonal temperatures early next week.

&&

.SHORT TERM...
Issued at 1157 PM PDT Wed Sep 23 2026
(Tonight through Friday)

There is a large variation in temperatures across our forecast
area, with 50s in a shallow marine layer along the coastline and 
60s, 70s and near 80 inland and at elevation. The warmth is due 
to ongoing thermal and height ridging aloft while a narrow channel
of cooler air over the coastal waters is undercutting the ridge. 
There is very little to no stratus or fog over the coastal waters 
since there is also warmer surface to near surface air temporarily
mixing in on northwest winds. Even though it's dry aloft i.e. 
good conditions for outward radiative cooling to help stratus and 
fog develop, the air/sea interface is not thermodynamically 
supportive of stratus/fog at the current time. However, 1000 mb 
NAM forecasts a rapidly southeastward moving cooler air mass 
arriving in our coastal waters between midnight and Thursday 
morning, which may briefly fall into syncopation with the 
remaining rhythm of radiative cooling in the early morning. This 
combination will likely help produce a few areas of coastal 
stratus and fog, while inland areas stay clear since the marine 
layer depth is forecast to remain near steady.

Daytime highs on Thursday will warm up similarly to Wednesday's
daytime highs with mid 60s to 70s near the immediate coastline,
70s/80s bayside to the 90s well inland. 

The ridge will weaken Friday with onshore winds deepening, sending
cooler air inland. Daytime highs Friday will range from the 60s/70s
coastside to the 80s well inland.

&&

.LONG TERM...
Issued at 1157 PM PDT Wed Sep 23 2026
(Friday night through next Wednesday)

For the weekend, 500 mb troughing will return once again which
will keep temperatures cooler than normal for late September. It
should be a beautiful weekend temperature-wise. After the weekend
cooling trend, temperatures will warm up again by the middle of 
next week.

&&

.AVIATION...
(12Z TAFS)
Issued at 445 AM PDT Thu Sep 24 2026

Not much in the way of a marine layer this morning. In fact, 12Z
TAFs are much more optimistic with mostly VFR. There is some early
morning clouds/fog trying to develop, but definitely struggling.
Highest likelihood for LIFR to IFR impacts will be HAF and MRY.
Breezy onshore this afternoon. Low conf for CIGs late tonight as
weak front approaches from the NW.

Vicinity of SFO...VFR through the period. 10-20 pct chc of low
CIGs toward the end of the TAF with a passing front. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...early morning LIFR CIGs trying to 
develop around Monterey Peninsula with impacts possible through 
16-17Z. VFR this afternoon.

&&

.MARINE...
(Today through Tuesday)
Issued at 445 AM PDT Thu Sep 24 2026

Light to moderate northerly breezes expected through early
Thursday night. Building high pressure after a passing cold front
will usher in fresh to strong breezes Friday into Saturday for
most of the waters. The stronger winds will lead to an elevated
sea state and hazardous conditions for small craft.

&&

.FIRE WEATHER...
Issued at 450 AM PDT Thu Sep 24 2026

Marine layer is pretty much non-existent overnight. That led much
less RH recovery across the district at both lower and higher
elevations. NGFS gave us a hit earlier in the night as the Timber
Fire had an northern perimeter flare up. Even FireGuard showed the
heat as well. Not completely surprised given temps in the 70s and
RH recovery around 30 pct near Timber. Otherwise, notes for today
will be another mild and dry day across the district. Hottest and
driest across the interior portions. Do expect an uptick with 
winds late tonight and Friday as a dry front moves through. Cooler
and wetter for Friday and over the weekend.

MM

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 5 AM PDT early this morning for 
     Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory until 3 AM PDT Thursday for Pt Arena to Pt 
     Reyes 10-60 NM.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM to 9 PM PDT Friday for Mry Bay.

     Small Craft Advisory from 9 AM Friday to 9 AM PDT Saturday for 
     Pigeon Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm-
     Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory from 9 PM this evening to 9 AM PDT Saturday 
     for Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory from 9 AM Friday to 3 PM PDT Saturday for 
     Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 
     NM.

&&

$$

SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...MM
MARINE...MM

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Prepared by Boulder-Creek.com Weather at: Thu Sep 24 06:30:03 PDT 2026