FXUS66 KMTR 241733
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1033 AM PDT Thu Sep 24 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 920 AM PDT Thu Sep 24 2026
- Warming trend persists today bringing pockets of moderate
HeatRisk across parts of the Bay Area and Central Coast.
- Cooler conditions arrive Friday into the weekend.
- Near seasonal temperatures early next week.
&&
.UPDATE...
Issued at 920 AM PDT Thu Sep 24 2026
Thursday is the last day of warm conditions this week, maintaining
moderate HeatRisk across the interior East/South Bay valleys and Big
Sur coastline. A parade of high clouds ahead of a dry cold front
pushes through today with the actual frontal passage occurring
overnight. Early Friday morning, a mix of low and high clouds with
moderate to strong onshore winds, around 15 to 20 mph primarily at
the coast, will result in widespread cooler conditions Friday into
the weekend. No precipitation is expected with this system as it
cruises through the Bay Area and Central Coast.
&&
.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...
(18Z TAFS)
Issued at 1032 AM PDT Thu Sep 24 2026
VFR. The lack of a better defined marine layer has resulted in
VFR conditions regionwide this morning. Onshore winds are forecast
to increase through late morning and become locally gusty at
times this afternoon. Winds ease slightly late in the night before
a dry frontal boundary pushes southward across the region
overnight and into Friday morning. The greatest potential for MVFR
or sub-MVFR conditions will be early Friday morning around HAF,
OAK, and MRY. In wake of the frontal passage on Friday, expecting
an increase north-northwesterly winds.
Vicinity of SFO...VFR through the TAF period. Onshore winds
increase this afternoon and again in wake of the early morning dry
frontal passage. There is a 20-30 percent probability of MVFR
ceilings just before sunrise on Friday, yet the greatest potential
will be over OAK. Thus, have left out of the TAFs at this time.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR. Onshore winds increase this
afternoon and ease after sunset. The greatest probability of sub-
MVFR conditions will be at MRY just before sunrise. Once the dry
frontal boundary passes, any low clouds that do develop will mix
out by around 17Z.
&&
.MARINE...
(Today through Tuesday)
Issued at 1032 AM PDT Thu Sep 24 2026
Light to moderate northerly breezes expected through early
Thursday night. Building high pressure in wake of a passing cold
front will usher in fresh to strong breezes Friday into Saturday
for most of the waters. Near gale force gusts will be possible in
the wind-prone areas nearshore. 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...RGass
MARINE...RGass
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Prepared by Boulder-Creek.com Weather at: Thu Sep 24 12:30:03 PDT 2026
From the National Weather Service
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