FXUS66 KMTR 301202
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
502 AM PDT Wed Sep 30 2026

...New FIRE WEATHER...

.KEY MESSAGES...
Updated at 1231 AM PDT Wed Sep 30 2026

 - Elevated fire weather conditions across the higher terrain
   through Thursday

 - Areas of moderate HeatRisk across the interior through Tuesday

 - Minor coastal flooding for bayshore locations along the San Francisco,
   San Pablo, and Monterey Bays Monday through Thursday

&&

.SHORT TERM...
Issued at 1231 AM PDT Wed Sep 30 2026
(Wednesday through Thursday)

With ridging nosing in from the Eastern Pacific Ocean and a low 
across the Desert Southwest, the upper-level pattern will support 
northerly/offshore flow through Thursday. Northerly/offshore winds 
will be strongest during the overnight periods and in the higher 
terrain. Mt. St. Helena gusted to 48 mph Tuesday morning with gusts 
of 25-35 mph elsewhere, similar conditions can be expected during 
the overnight periods through Thursday morning. The combination of 
dry and windy conditions will result in elevated fire weather 
conditions across the higher terrain through Thursday. Temperatures 
will be 5 to 10 degrees above normal with the marine layer 
struggling to form. If it is able to form, it will be compressed 
around 500 feet and remain confined to the coast. Minor coastal 
flooding for bayshore locations along the San Francisco, San Pablo, 
and Monterey Bays will continue during the highest high tides 
through Thursday.

&&

.LONG TERM...
Issued at 1231 AM PDT Wed Sep 30 2026
(Friday through Tuesday)

Global ensemble clusters are in agreement that anomalously high 
heights will be across our area through Tuesday. 500 mb heights and 
850 mb temperatures are forecast to be near the 90th percentile for 
the first week of October, which is 588 decameters and 21 degrees 
Celsius, respectively. Saturday will likely be the peak of the heat 
as upper-level longwave ridging drifts in from the Eastern Pacific 
Ocean. Nonetheless, temperatures will be 10 to 15 degrees above 
normal with moderate HeatRisk away from the immediate coast through 
Tuesday. The marine layer will likely still struggle to form; if 
it's able to form, it will be compressed around 500 feet and remain 
confined to the coast.

&&

.AVIATION...
(12Z TAFS)
Issued at 443 AM PDT Wed Sep 30 2026

It's VFR except for patchy low stratus and fog /IFR-LIFR/ over the
Monterey Bay and along the shoreline. A few additional patches of
low stratus and fog /IFR-LIFR/ will develop during morning otherwise
VFR will prevail today. Areas of coastal low stratus and fog /IFR-LIFR/
will redevelop tonight and Thursday morning.

Vicinity of SFO...VFR today, then stratus /IFR/ develops by mid 
evening and prevails tonight to 18z Thursday. Light northeast wind
this morning, shifting to westerly 10 to 20 knots in the afternoon.
Wind decreasing to 5 knots tonight and Thursday morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Low stratus and fog /IFR-LIFR/ develops 
through mid to nearly late morning then mixes out for the afternoon
to early evening. Low stratus and fog /IFR-LIFR/ return tonight
and Thursday morning. Light easterly to southeasterly cool air
drainage winds in the morning, shifting to onshore near 10 knots
in the afternoon and early evening.

&&

.MARINE...
(Today through Monday)
Issued at 430 AM PDT Wed Sep 30 2026

Hazardous conditions for small craft will continue through tonight
mainly across the outer waters. Conditions will improve later this
week and weekend as northwesterly breezes diminish to become
gentle to moderate. Rough to very rough seas today will subside to
moderate by Friday.

&&

.FIRE WEATHER...
Issued at 502 AM PDT Wed Sep 30 2026

A high pressure system will move in from the west and compress the
marine layer to approximately 500 feet. Hot and dry conditions
will prevail through late week and weekend. Expect poor overnight
humidity recoveries, with overnight relative humidities as low as
20-30% above the marine layer.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 5 PM PDT Thursday for CAZ006-506-
     508-529-530.

PZ...Small Craft Advisory until 3 AM PDT Thursday for Pigeon Pt to Pt 
     Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

     Gale Warning until 9 AM PDT this morning for Pt Arena to Pt 
     Reyes 10-60 NM.

&&

$$

SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Canepa
MARINE...Canepa

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Prepared by Boulder-Creek.com Weather at: Wed Sep 30 08:30:03 PDT 2026