FXUS66 KMTR 112316
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
416 PM PDT Fri Sep 11 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1201 PM PDT Fri Sep 11 2026
- Temperatures near seasonal averages through the next week
- Breezy onshore winds this weekend
&&
.SHORT TERM...
Issued at 1201 PM PDT Fri Sep 11 2026
(This evening through Saturday night)
The return of the marine layer (around 1600 feet per 12Z OAK
Upper Air Sounding) resulted in widespread coverage of stratus
this morning, with the exception of the East Bay interior valleys.
Since then, clouds are quickly retreating to the coast and are
forecast to linger off of the Central Coast for much of the day.
However, a weak frontal boundary approaching the North Bay is
likely to bring a return of clear skies off of the North Bay coast
this afternoon.
Despite mostly sunny sky conditions across the interior, today
will be much cooler than previous days as the region remains in
between mid/upper level cut-off low off of the British Columbia
coast and high pressure confined to southern California, Nevada,
and Arizona. Less confidence tonight in the amount of stratus that
returns to the region as the aforementioned frontal boundary
moves southward and then weakens.
The cut-off low will shift southward before moving into the
Pacific Northwest Saturday night and into Sunday. As such,
westerly to northwesterly winds will increase tomorrow afternoon
and persist through Saturday night ahead of yet another frontal
boundary. The strongest wind gusts will be between 25 to 35 mph
with favored gaps, passes, and coastal regions gusts up to 45 mph.
This cold front will sweep across the North Bay and Bay Area
Saturday night into Sunday with no measurable precipitation
forecast.
&&
.LONG TERM...
Issued at 1201 PM PDT Fri Sep 11 2026
(Sunday through next Thursday)
In wake of the frontal passage, offshore flow is forecast from
Sunday night and into Monday night as 925 mb winds become
northerly to northeasterly. However, the offshore flow is not
forecast to be much greater than 20 kt (23 mph) at 925 mb,
limiting fire weather concerns. Onshore winds are forecast to
persist in the lower elevations with the strongest in the early
afternoon and through the evening hours. Thus, the marine layer
looks to hold around 1500 feet in depth through the weekend. As
mentioned in the Fire Weather section of the AFD below, areas
above the marine layer often experience nocturnal drying (during
the overnight hours). That will be the case during this offshore
event. The trough axis is forecast to move into the northern
Rockies and the northern Plains early next week, diminishing the
offshore wind potential.
Lingering troughiness along the West Coast will maintain cooler
than average temperatures for much of next week. This will give
way to temperatures warming into the 60s to lower 70s along the
northwest facing coastal locations and low to upper 70s around the
Santa Cruz region, bayshore, and coastal adjacent valleys.
Meanwhile, interior valleys are forecast to reach into the upper
70s to mid 80s with the warmest interior valleys of the Central
Coast reaching into the low 90s.
&&
.AVIATION...
(00Z TAFS)
Issued at 416 PM PDT Fri Sep 11 2026
IFR-MVFR stratus lingers at the immediate coast, with satellite
imagery revealing clearing skies associated with a weak frontal
boundary lurking offshore. Will need to monitor the clearing as it
pertains to stratus development this evening and overnight. As it
is, the current forecast has a moderate confidence that the stratus
moves inland this evening as the marine layer remains around 1000-
1500 feet. High resolution models are a little more optimistic in
terms of keeping inland terminals VFR, but opted to maintain
continuity with the previous forecast. Any stratus that forms will
dissipate back to the immediate coast through the course of Saturday
morning. Moderate onshore pattern winds with some strong gusts will
continue through the evening hours, turning lighter overnight before
resuming Saturday afternoon.
Vicinity of SFO... VFR through the day with moderate confidence that
VFR conditions persist through the TAF period. Moderate northwest
winds persist into the evening, with wind speeds slightly decreasing
overnight before strong and gusty winds come to the terminal
Saturday afternoon.
SFO Bridge Approach... Similar to SFO.
Monterey Bay Terminals... VFR with moderate northwest winds through
the evening, moderate confidence that LIFR ceilings develop
overnight at the terminals as winds become light. Stratus retreats
back to the immediate coast on Saturday morning with moderate
northwest winds resuming in the afternoon.
&&
.MARINE...
(Tonight through next Wednesday)
Issued at 416 PM PDT Fri Sep 11 2026
Hazardous conditions for small craft will prevail late this
weekend through mid next week. A moderate to fresh NW breeze will
increase today into tomorrow to a strong breeze by early Sunday
and continue into the early work week. Near gale force gusts to
occasional gale force gusts are expected along the inner waters
from Pigeon Point to Point Piedras Blancas, the Monterey Bay, and
in portions of the San Francisco and San Pablo Bays. Moderate
seas will build, becoming 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.
Flynn
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM to 9 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 9 PM PDT Saturday for Pt Arena to Pt
Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt
to Pt Pinos 0-10 nm.
Small Craft Advisory until 9 AM PDT Saturday for Pt Arena to Pt
Reyes 10-60 NM.
&&
$$
SHORT TERM...RGass
LONG TERM....RGass
AVIATION...DialH
MARINE...Kennedy
Visit us at www.weather.gov/sanfrancisco
Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea
Prepared by Boulder-Creek.com Weather at: Fri Sep 11 20:30:03 PDT 2026
From the National Weather Service
|