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 06:30:03 PDT 2026
From the National Weather Service
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