FXUS66 KMTR 121558
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
858 AM PDT Sat Sep 12 2026

...New UPDATE, MARINE...

.KEY MESSAGES...
Updated at 856 AM PDT Sat Sep 12 2026

 - Breezy onshore winds Saturday afternoon through Sunday
   afternoon

 - Temperatures near seasonal averages through next week


&&

.UPDATE...
Issued at 856 AM PDT Sat Sep 12 2026

As mentioned in the Short Term section of the AFD below, a weak 
frontal boundary that moved across the North Bay and Bay Area 
yesterday evening scoured out low-level marine layer clouds. 
However, the marine layer on the 12Z OAK Upper Air Sounding reported 
the marine layer depth at around 1,500 feet. Thus, stratus was 
confined to the Monterey Bay Region, down the Salinas Valley and 
just off of the Big Sur coastline. These low clouds are forecast to 
dissipate throughout late morning and early afternoon. All that 
said, the ongoing forecast remains on track at this time with no 
updates anticipated this morning.  

RGass

&&

.SHORT TERM...
Issued at 1017 PM PDT Fri Sep 11 2026
(Tonight through Saturday night)

Satellite imagery reveals something pretty peculiar for this time of 
year, so soon after the marine layer redeveloped after a couple days 
of heat: clear skies across most of the Bay Area and Central Coast, 
as a weak frontal boundary helped to scour out the marine layer 
clouds over the afternoon and evening hours. Observations from the 
Bodega Bay profiler suggest that the marine layer itself is still 
there, hovering around 1000-1500 feet, so it remains to be seen if 
any of the remaining stratus, most notably the patch on the eastern 
side of Monterey Bay, can linger through the night, and whether any 
new stratus can form overnight. Looking at the high resolution 
output, it doesn't seem likely and many of us may see the skies 
remain clear overnight. 

A strong cutoff low hovers off the coast of the Pacific Northwest, 
helping contribute to the cooling trend that started Thursday night 
and continued through the following day. Through Saturday the cutoff 
low is expected to inch its way into the state of Oregon, helping to 
tighten the local pressure gradient and building breezy and strong 
onshore winds in the afternoon and evening hours on Saturday before 
winds ease Sunday morning. Wind gusts will generally reach 25 to 35 
miles per hour, with favored gaps, passes, valleys, and coastal 
areas seeing gusts to 45 miles per hour.

Morning lows will hover in the middle 50s to lower 60s for the lower 
elevations, and into the middle 60s for the higher elevations. 
Afternoon highs range from the upper 70s to middle 80s for the 
inland valleys, up to the 90s in the warmest spots of the far 
interior Central Coast, the upper 60s to the middle 70s close to the 
Bays, and the lower to middle 60s along the Pacific coast.

&&

.LONG TERM...
Issued at 1017 PM PDT Fri Sep 11 2026
(Sunday through next Friday)

The trough axis continues moving eastwards Sunday into the early 
part of next week, helping to relax the pressure gradient and lower 
the wind gusts for Sunday. Despite the trough axis moving into the 
northern Rockies and Plains, some troughing influence will remain 
across the West Coast, keeping temperatures near to slightly below 
seasonal averages. The pattern will remain remarkably stable through 
the remainder of the 7-day outlook. Highs will range from the middle 
70s to the middle 80s inland, the upper 60s into the 70s close to 
the Bays, and the lower to middle 60s along the Pacific coast. Low 
clouds will likely develop overnight into the morning, while breezy 
onshore winds will set up in the afternoon and evening hours. Longer-
term outlooks suggest a lean towards temperatures above seasonal 
averages and precipitation totals near to above seasonal averages 
towards the latter part of September.

&&

.AVIATION...
(12Z TAFS)
Issued at 524 AM PDT Sat Sep 12 2026

It's VFR except for patchy stratus and mist/fog /MVFR-LIFR/ this
morning. Surface to lower level cool air advection on northwest 
winds will increase today, the wind flow trapped beneath a lower 
level temperature inversion resulting in areas of strengthening, 
gusty onshore winds. The SFO-SAC pressure gradient is forecast to 
increase to 4 mb to 5 mb in the afternoon. September sun angle 
surface warming and vertical mixing will erode any remaining 
stratus by late morning. Gusty onshore winds may continue through
the evening before diminishing tonight. 

Vicinity of SFO...VFR. West wind 5 knots increasing to 25 to 35
knots in the afternoon, continuing through the evening and may
take to 3 am Sunday before diminishing to 15 knots. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR except patchy stratus and mist/fog
/IFR-LIFR/ nearby during the morning. Onshore winds 5 knots
increasing to 10 to 20 knots with occasional gusts to 25 knots in
the Salinas Valley late morning, afternoon and early evening.
Winds diminishing to 10 knots tonight and Sunday morning.

&&

.MARINE...
(Today through Thursday)
Issued at 856 AM PDT Sat Sep 12 2026

Hazardous conditions for small craft prevail this weekend through
the middle of next week. Winds increase today with a strong
breeze to develop by early Sunday and continue into the middle of
next week. Widespread near gale force gusts are likely Sunday into
early Monday with 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 625 AM PDT Sat Sep 12 2026

The marine layer remains around 1,500 feet in depth per 12Z OAK 
Upper Air Sounding. However, the stratus pattern does not 
represent this as mostly clear sky conditions prevail early this 
morning with stratus hugging the southern portion of the Monterey 
County coastline. However, overnight humidity recoveries have been
good to excellent in elevations generally below 1,500 feet. Above
that, humidity levels remain largely in the teens and twenties as
of 6 AM PDT Saturday. Thus, not expecting much humidity retention
this afternoon with the higher elevations not forecast to exceed
25-35%. The depth of the marine layer will hold steady between 
1,000-1,500 feet through the weekend. Areas above the marine layer
often experience nocturnal drying that will likely continue 
into early next week. 

RGass

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 AM PDT Sunday for SF Bay N of Bay 
     Bridge.

     Small Craft Advisory from 3 PM to 9 PM PDT Sunday for SF Bay N 
     of Bay Bridge.

     Small Craft Advisory until 3 PM PDT Sunday for Mry Bay-Pigeon Pt 
     to Pt Pinos 0-10 nm.

     Gale Warning from 3 PM to 9 PM PDT Sunday for Mry Bay-Pigeon Pt 
     to Pt Pinos 0-10 nm.

     Small Craft Advisory until 3 AM PDT Monday for Pt Arena to Pt 
     Reyes 0-10 nm.

     Small Craft Advisory until 3 AM PDT Monday for Pt Reyes to 
     Pigeon Pt 0-10 nm.

     Small Craft Advisory until 9 PM PDT this evening for Pt Pinos to 
     Pt Piedras Blancas 0-10 nm.

     Gale Warning from 9 PM this evening to 9 PM PDT Sunday for Pt 
     Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory until 9 AM PDT this morning for Pt Arena to 
     Pt Reyes 10-60 NM.

     Small Craft Advisory from 3 PM Sunday to 3 AM PDT Monday for Pt 
     Arena to Pt Reyes 10-60 NM.

     Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Monday 
     for Pigeon Pt to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Canepa
MARINE...Kennedy

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Prepared by Boulder-Creek.com Weather at: Sat Sep 12 10:30:04 PDT 2026