FXUS66 KMTR 291237
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
537 AM PDT Sat Aug 29 2026

...New UPDATE...

.KEY MESSAGES...
Updated at 909 PM PDT Fri Aug 28 2026

 - Clear skies and cool temperatures today

 - Cooler weather continues into next week

&&

.UPDATE...
Issued at 535 AM PDT Sat Aug 29 2026

A Dense Fog Advisory has been issued for the Sonoma County
valleys, particularly along Highway 101 from healdsburg to Novato,
through 9 AM today. Observations from the Sonoma County, Petaluma,
and Novato airport weather stations and webcam images from the
Highway 101 corridor support the presence of dense fog with
visibilities of one quarter of a mile or less. Drivers should slow
down, use low-beam headlights, and leave plenty of space in front
of their vehicles.

DialH

&&

.SHORT TERM...
Issued at 909 PM PDT Fri Aug 28 2026
(Tonight through Sunday)

While there were some light showers Friday, the lightning never 
happened and that threat is now over. The 00Z sounding measured 
1.32" of precipitable water. That's well over the 90th percentile
(1.04"), and near the maximum recorded for this date (1.38").
Despite this near record moisture, dry air is moving in from the 
northwest remarkably fast. The ECMWF ensemble mean predicts the PW
will drop from 1.38" Friday to around 0.5" Saturday. That means
the atmospheric moisture is decreasing from well over the 90th 
percentile all the way down to the 10th percentile in only 12-24 
hours.

As a result of the much drier air, the skies will be mostly clear
Saturday. The marine layer is trying to re-organize, but any 
stratus will likely be patchy and evaporate in the mid to late morning.
The mid and high level clouds are already clearing and will not 
return anytime soon. Despite the sunshine, temperatures will
remain several degrees cooler than normal this weekend.

&&

.LONG TERM...
Issued at 909 PM PDT Fri Aug 28 2026
(Sunday night through next Friday)

Upper level troughing will persist through the week, with a few
embedded shortwave features bringing some early rain to the 
Pacific Northwest. In the Bay Area, rain is less likely, but the 
cooling trend will continue through at least the middle of the 
week. Max temperatures will be roughly 10-15 degrees below normal
from Monday through Wednesday. The 850 mb temperature is expected
to drop below the 25th percentile (16.1C) by Tuesday morning.  

&&

.AVIATION...
(12Z TAFS)
Issued at 421 AM PDT Sat Aug 29 2026

IFR-LIFR stratus is developing into the Sonoma County valleys, 
through the Golden Gate into the SF Bay Area, and across Monterey 
Bay and into the northern Salinas Valley. Limited further expansion 
is forecast tonight as the marine layer remains relatively 
compressed at around 1000-1500 ft deep. Stratus will retreat to the 
immediate coast after sunrise with moderate onshore pattern winds 
developing in the afternoon and evening hours. Tonight, lower 
confidence in the ceiling heights as a deepening marine layer should 
result in some higher ceilings, but otherwise the stratus deck 
should return to most of the areas that it currently covers.

Vicinity of SFO... IFR stratus over the immediate terminal area will 
persist through the post-sunrise hours, moderate confidence on the 
clearing time. Moderate west-northwest winds with strong gusts will 
develop in the afternoon and evening, with stratus returning to the 
terminal area tonight. 

SFO Bridge Approach... Lower confidence for stratus development 
along the approach path through the morning. Otherwise similar to 
SFO.

Monterey Bay Terminals... LIFR stratus and patchy fog continue 
through the morning. Gentle to moderate northwest winds will develop 
in the afternoon and evening hours, with stratus returning somewhat 
early in the evening hours.

&&

.MARINE...
(Today through Thursday)
Issued at 421 AM PDT Sat Aug 29 2026

Fresh northwest breezes with occasional near gale force gusts and
a long period southerly swell continue through the weekend. The
long period southerly swell peaks today around 17 to 18 seconds
and gradually diminishes by Sunday night. Wind driven seas briefly
build to rough this afternoon into Sunday and gradually subside
to moderate through the next week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Dense Fog Advisory until 9 AM PDT this morning for CAZ506.

PZ...Small Craft Advisory from 9 AM this morning to 3 AM PDT Sunday 
     for Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm.

     Small Craft Advisory until 6 AM PDT early this morning for 
     Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 
     NM-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.

     Small Craft Advisory from 9 AM this morning to 3 AM PDT Monday 
     for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 
     NM.

     Small Craft Advisory from 9 AM this morning to 9 PM PDT Sunday 
     for Pigeon Pt to Pt Pinos 10-60 NM-Pt Pinos to Pt Piedras 
     Blancas 0-10 nm.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...DialH
MARINE...DialH

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Prepared by Boulder-Creek.com Weather at: Sat Aug 29 08:30:02 PDT 2026