FXUS66 KMTR 100445
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
945 PM PDT Wed Sep 9 2026

...New AVIATION, MARINE...

.KEY MESSAGES...

 - Warming and drying trend will bring widespread moderate to
   major HeatRisk through Thursday

 - Cooler temperatures, closer to normal, Friday into the weekend

&&

.UPDATE...
Issued at 900 PM PDT Wed Sep 9 2026

Temperatures remain very warm for the evening with downtown San
Francisco coming in at 83 as of the last report, while other spots
in the valleys check in at the lower to middle 80s. The latest 
forecast update has bumped up Thursday's afternoon highs and 
morning lows quite significantly, as high clouds from the remnants
of Tropical Storm Marie continue to inhibit radiational cooling 
overnight. This will also increase the risk for heat related 
illnesses as the body will not have much of a chance to cool down 
and recover from the heat tonight, particularly outdoors or in 
buildings without air conditioning. Make sure to drink plenty of 
water and try to cool yourself down any way you can tonight.

DialH

&&

.SHORT TERM...
1231 PM PDT Wed Sep 9 2026
(Today through Friday)

A northward intrusion of mainly mid and high level tropical 
moisture from the remnants of Marie continues through the North
Bay Area with more filling in overnight. Warm temperatures will 
continue tonight with the incoming cloud layers greatly reducing 
radiative cooling. Sub- cloud layer dry air does at times tend to 
stay land- locked over the highly varied terrain of CA, until 
diurnal mixing, diffusion, wind transport and/or precipitation get
going to thoroughly mix in the higher humidity to ground level.
The radar KMUX currently shows showers moving by about 70 miles 
offshore. This bears close monitoring in the nearest term.

No changes to the forecast at this time. A Heat Advisory remains
in effect for the entire forecast area until 10 PM Thursday. Strong
high pressure will result in warm morning low temperatures and 
daytime highs in the 90s to lower 100s over much of the forecast 
area. Along the immediate coastline an afternoon sea breeze may 
help nudge temperatures back down. This is a complex pattern, 
please stay tuned for the latest updates. Cooler, more seasonal 
temperatures are expected by Friday.

From the earlier forecast discussion:

Please remember these tips to help mitigate impacts from heat 
exposure:

-Suspend unnecessary outdoor activities during the extreme heat, but 
if you must be outdoors, take frequent breaks in the shade  or AC 
and drink cool water.
-Know the signs and symptoms of Heat Exhaustion vs. Heat Stroke! 
Heat Stroke can be deadly if not treated immediately by a medical 
professional. Call 911 if you suspect someone is suffering from Heat 
Stroke.
-Wear a life jacket, swim near a lifeguard, and check conditions 
before entering the water if going to a river or ocean to cool off. 
Rivers and the ocean are extremely cold, and Cold Water Shock can 
turn into paralysis and drowning if you are not careful.
-Use a cool and damp towel on your body if you do not have AC and 
are feeling hot. Or, take a cool shower or bath.
-Do not leave kids or pets in a parked car.
-Ensure pets and livestock have access to shade and water.

&&

.LONG TERM...
1231 PM PDT Wed Sep 9 2026
(Saturday through next Wednesday)

The main concern is the short term. 

A weekend cooling trend remains in the forecast. The strong ridge
over our forecast area will weaken. Dry weather is forecast.

&&

.AVIATION...
(06Z TAFS)
Issued at 941 PM PDT Wed Sep 9 2026

VFR through tomorrow evening with some MVFR to IFR cigs 
returning by the end of the TAF period. Overall conf is moderate.

Vicinity of SFO...Onshore flow will ease overnight, but remain 
VFR with high clouds. Onshore kicks up again tomorrow afternoon 
with gusts over 20 kt into the evening rush. Very end of the 30 hr
TAF will see lower cigs return to SF Bay with impacts to SFO/OAK.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through tomorrow afternoon. MVFR to
IFR cigs return tomorrow evening as the marine layer tries to re-
develop.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 941 PM PDT Wed Sep 9 2026

A few lingering showers remain over the northern waters thanks to
passing tropical moisture. Then, gentle to moderate northwesterly
breezes with a smaller sea state will continue through Thursday.
By Friday, northerly winds increase thank to a stronger north to
south pressure gradient. A strong northwest breeze is expected
Saturday and Sunday. A moderate SW swell from distant tropical
cyclones will continue through the week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 1 AM PDT Thursday for CAZ006-506-
     508-529-530.

     Heat Advisory until 10 PM PDT Thursday for CAZ006-502>506-
     508>510-512>518-528>530.

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

&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...MM
MARINE...MM

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Prepared by Boulder-Creek.com Weather at: Wed Sep 9 22:30:03 PDT 2026