FXUS66 KMTR 020444
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
944 PM PDT Tue Sep 1 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 107 PM PDT Tue Sep 1 2026

 - Cooler weather continues through the week

 - Beneficial wetting rain expected in the North Bay through 
   Thursday

&&

.UPDATE...
Issued at 517 PM PDT Tue Sep 1 2026

The 00Z sounding measured the marine layer at 5,200 ft. That's
about as deep as possible before it loses it's structure. In fact 
cumulus clouds are surviving within the marine layer. The deep 
marine layer also allowed temperatures to climb higher than 
expected in the coastal areas. If the marine layer survives the
night we will see a double inversion pattern. Meanwhile light rain
is approaching the North Bay and should be there Wednesday
morning.

&&

.SHORT TERM...
Issued at 107 PM PDT Tue Sep 1 2026
(This evening through Wednesday night)

Mostly clear sky conditions have returned to the Central Coast 
with scattered low clouds across the Bay Area and North Bay. There
are also high clouds associated with an approaching frontal 
boundary across the North Bay. As such, temperatures today will be
5-15 degrees below normal as the 850 mb temperature drops below 
10C/50F for the first time since May. Additionally, there is a 
chance for for light rain and/or drizzle across the North Bay 
tonight into Wednesday morning with pre-fronatal coastal drizzle 
for areas to the south. 

Low clouds will spread back inland overnight and into Wednesday 
morning with temperatures generally the 50s across much of the 
region and in the 40s in the higher elevations. Similar conditions
are forecast for Wednesday with another disturbance moving in 
from the northwest Wednesday night into Thursday. This will bring 
increasing potential for light rain across the North Bay and 
portions of the Bay Area. The greatest potential to see greater 
than 0.25" will be in the coastal ranges of the North Bay and 
0.10" in and around Santa Rosa and the Sonoma County valleys by 
Thursday morning. Rainfall amounts drastically drop off the 
further south you go. 

&&

.LONG TERM...
Issued at 107 PM PDT Tue Sep 1 2026
(Thursday through next Monday)

Heading into this upcoming weekend, there is the potential we see a 
slight warming trend high pressure over the central United States 
builds westward. However, troughing off of the West Coast will main 
cooler than average temperatures throughout the weekend. 

Ensemble clusters diverge heading into next week. As such, still 
keeping an eye on tropical development over the eastern Pacific 
Ocean for any northward movement of tropical moisture. However, 
the latest guidance is indicating the track of TS Marie should 
stay well to our south, potentially bringing impacts to southern 
California. For more information on tropical developments visit 
nhc.noaa.gov. 

&&

.AVIATION...
(06Z TAFS)
Issued at 944 PM PDT Tue Sep 1 2026

It's currently VFR at the airport terminals except KHAF reports 
low clouds /IFR/. Mid to upper level troughing will pass across 
the forecast area resulting in variable ceilings /VFR-MVFR-IFR/ 
tonight and Wednesday morning with generally improving conditions 
to MVFR-VFR late Wednesday morning and afternoon.

Vicinity of SFO...VFR-MVFR with low clouds forming overnight and
Wednesday morning. Conditions VFR Wednesday afternoon and early
evening, MVFR with low clouds returning mid Wednesday evening.
Southwest to west wind 5 to 15 knots.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR-MVFR with a few patches of low clouds
forming overnight and Wednesday morning. Conditions VFR Wednesday
afternoon and early evening then low clouds /MVFR/ returns mid
Wednesday evening. Variable winds 5 knots or less becoming west to
northwest 5 to 15 knots Wednesday afternoon and evening.

&&

.MARINE...
(Tonight through next Monday)
Issued at 920 PM PDT Tue Sep 1 2026

Light northwesterly breezes with occasional moderate breezes will
persist through the week with slight to moderate wind driven
seas. Tropical cyclone activity will produce long period southerly
swell for the end of the week into the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...Canepa
MARINE...Canepa

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Prepared by Boulder-Creek.com Weather at: Tue Sep 1 22:30:03 PDT 2026