FXUS66 KMTR 111151
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
451 AM PDT Fri Sep 11 2026
...New AVIATION, MARINE, FIRE WEATHER...
.KEY MESSAGES...
Updated at 1201 AM PDT Fri Sep 11 2026
- Temperatures near seasonal averages through the next week
- Breezy onshore winds this weekend
&&
.SHORT TERM...
Issued at 1201 AM PDT Fri Sep 11 2026
(Today and tonight)
What a difference a day makes. The continuing development of a
cutoff low off the coast of British Columbia has led to a remarkable
cooling through the evening and overnight hours, the return of a
marine layer of around 500-1000 feet, and a stratus deck over the
coastal regions and through the Petaluma Gap and the Golden Gate. As
of midnight, temperatures across the Bay Area and Central Coast are
running around 5 to 25 degrees below what they were 24 hours prior.
Through the day, the aforementioned cutoff low will strengthen as it
parallels the coast of the Pacific Northwest. Morning lows will
range from the middle 50s to lower 60s in the lower elevations, and
the middle 60s to the middle 70s in the higher elevations, while
afternoon highs will top out in the middle 80s to the lower 90s in
the inland valleys, the upper 90s to the triple digits in the
warmest spots of southern Monterey County, the upper 60s to the
lower 80s close to the Bays, and the lower to middle 60s along the
Pacific coast.
&&
.LONG TERM...
Issued at 1201 AM PDT Fri Sep 11 2026
(Saturday through Thursday)
The cooling trend continues into the weekend as the cutoff low moves
into the Pacific Northwest, allowing for further development of the
onshore flow and marine layer to take place. By the weekend, highs
will drop into the middle 70s to middle 80s inland and the upper 60s
to upper 70s close to the Bays. Breezy onshore winds are expected
through the weekend as the passing cutoff low tightens the pressure
gradient over the northern half of California. Regarding the SFO-WMC
gradient, model output has kept the peak gradient somewhere in the
10 to 15 mb range late on Saturday, with widespread gusts of 25 to
35 mph possible Saturday evening into Sunday morning. Favored gaps,
passes, and coastal regions could see gusts to 45 mph.
The trough axis should move into the northern Rockies and the
northern Plains for the early part of next week, but the general
pattern should remain rather zonal for the remainder of the 7-day
outlook, and temperatures should remain more or less stable with
highs near or slightly below seasonal averages.
&&
.AVIATION...
(12Z TAFS)
Issued at 429 AM PDT Fri Sep 11 2026
As expected the marine layer has returned and is bringing IFR to
LIFR stratus to the coastal terminals. The 12Z balloon just
measured the marine layer depth at 1600 feet, which is deep enough
to reach SJC, but not LVK. APC is still VFR, but could go either
way at this point. The stratus will clear around 18-19Z for all
but the coastal terminals. HAF will likely stay IFR or worse
through the entire TAF period. Stratus will return to most
terminals overnight.
Vicinity of SFO...The terminal is reporting IFR ceilings, which
will persist through at least 17Z, and possibly through 19Z before
VFR conditions return through the afternoon. A moderate onshore
breeze will arrive this afternoon. Stratus is likely to return
between 06Z and 12Z tonight.
SFO Bridge Approach...Ceilings will clear a couple hours earlier
than the terminal, and form a couple hours later.
Monterey Bay Terminals...LIFR conditions will persist through the
morning. SNS will very likely clear by late morning, but MRY is
more of a toss up. If there is any clearing at MRY, it will only
last for 6 hours or so before the marine layer stratus returns.
&&
.MARINE...
(Today through Wednesday)
Issued at 429 AM PDT Fri Sep 11 2026
A moderate to fresh NW breeze will increase over the next 24
hours, with a fresh to strong breeze expected through the weekend
and into next week. Seas are currently moderate and will build to
rough by Monday in response to the stronger winds.
&&
.FIRE WEATHER...
Issued at 429 AM PDT Fri Sep 11 2026
A new weather pattern will influence conditions over the Timber
and Plaskett Fires in Monterey County. The marine layer has
returned and is 1,600 feet deep as measured by the 12Z balloon.
This height should be fairly consistent through the day before
some expansion this weekend as the trough moves through. While the
marine layer brings much cooler and more humid conditions to the
coast, areas above the marine layer often experience nocturnal
drying as the dry air above the clouds rolls in simultaneously
with the low clouds. In the late morning the clouds will mix out
as the layers become less stratified, often increasing dew point
during the warmest part of the day.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM to 3 PM PDT Saturday for Mry Bay-
Pigeon Pt to Pt Pinos 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm-
SF Bay N of Bay Bridge.
Small Craft Advisory until 3 PM PDT Saturday 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.
Small Craft Advisory from 9 AM this morning to 9 PM PDT this
evening for Pigeon Pt to Pt Pinos 0-10 nm.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Flynn
MARINE...Flynn
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Prepared by Boulder-Creek.com Weather at: Fri Sep 11 06:30:03 PDT 2026
From the National Weather Service
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