FXUS66 KMTR 030541
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1041 PM PDT Wed Sep 2 2026

...New SHORT TERM, LONG TERM, BEACHES...

.KEY MESSAGES...
Updated at 1010 PM PDT Wed Sep 2 2026

 - Beneficial rain Thursday, mainly in the North Bay

 - Hazardous beach conditions this weekend

&&

.SHORT TERM...
Issued at 1010 PM PDT Wed Sep 2 2026
(Tonight through Friday)

The marine layer is gone. A cold front is currently located about 
200 miles west of San Francisco and is supported in the upper levels 
by a 500 mb trough and a meridional jet stream. We saw some pre-
frontal rain in the North Bay on Wednesday. Santa Rosa received 
0.08" and Mt. Tam recorded 0.64". That was just the warm-up. The 
main event will occur Thursday morning as the front moves through. 
Models have been trending wetter, and we're now expected around 1/4" 
in Santa Rosa through the morning and up to 1" in the mountains. 
That's not enough to cause any major issues, but it is real rain,
especially for this time of year. The normal rainfall for the 
entire moth of September is 0.15" at Santa Rosa. Expect slick 
roadways in the North Bay Thursday morning.

As the front continues to march south, the associated rain should 
cross the Golden Gate by midday, but it will be losing upper level 
support and start to rapidly weaken. While a good portion of the 
Bay Area should see some rain, it likely won't be more than a few 
hundredths outside of the coastal mountains. The Central Coast 
will be even drier, and will have to wait until Thursday evening 
to see if any rain will fall.

In addition to rain, this front will bring NW winds with gusts up to 
25 mph for most. Stronger gusts of 30-40mph are expected through 
favored gaps/passes, and in the Salinas Valley. We'll obviously have 
more cloud cover Thursday as well, keeping the temperatures cool
and comfortable.

After the front passes, skies will clear from North to South through 
Thursday evening. As the skies clear, radiational cooling overnight 
will help the marine layer will start to reform. While there is 
still some uncertainty with the timing, marine layer stratus will 
likely return to the North Bay by Friday morning, but may take until 
Saturday or even Sunday to reach the Central Coast.

&&

.LONG TERM...
Issued at 1010 PM PDT Wed Sep 2 2026
(Friday night through next Wednesday)

Speaking of this weekend, a Beach Hazards Statement is in effect 
from Friday through Monday as southerly swell from multiple distant 
hurricanes reaches the coast. Days when it's nice outside but the
ocean is energetic are typically the most deadly. On top of that
it's a holiday weekend. Please refer to the Beaches section below
for more details.

Behind the front the temperature outside of the newly forming marine 
layer will start to warm up through the weekend. At 500 mb the 
trough over the coast will become a pseudo cut-off low. While it 
detaches from the 500 mb flow, a healthy jet finger will continue to 
provide some upper level divergence through the weekend. 
Nevertheless the low pressure will gradually fill. Meanwhile high 
pressure over the Southwest will start to influence the weather, 
allowing temperatures to rebound back to normal by Monday. 

As Hurricane Marie now looks like it will take a more westerly track 
out to sea, the residual moisture impacts are much less likely to 
reach any further north than Southern California this weekend. 
Models are also showing a slug of dry air Sunday over the Central 
Coast that blocks the less dense tropical air mass from moving 
north. The deterministic ECMWF shows 1.8" of PW at Los Angeles 
Sunday afternoon, while Monterey has 0.5". That would give 
Southern California a decent amount of rain, but nothing for the 
Bay Area. It's a similar story with instability. Not a single 
member of the ECMWF ensemble has MUCAPE over 50 J/kg north of Pt. 
Conception. There is always the chance that the tropical moisture 
rides over this dry air mass, opening the door for dry 
thunderstorms. There's no direct support for that in the model 
guidance at the moment, but pattern recognition suggests it's 
worth keeping an eye on. 

While this weekend now looks like it will probably be dry, there is 
a hint in the guidance that the remnants of Marie will eventually 
get caught up in the persistent SW flow if the cut-off low can 
survive long enough. If that happens, we may see some associated 
moisture by the middle of next week.

&&

.AVIATION...
(06Z TAFS)
Issued at 957 PM PDT Wed Sep 2 2026

Minimal changes to the TAF package this evening. The near term 
changes covered stratus that has started to form along the coast 
and in some of the valleys. Outside of that, we await the arrival of 
a cold front. The highest chances for rain will be for the North Bay 
terminals with chances decreasing around the San Francisco Bay.
Heavier pockets of rain may bring reduced visibility at times, but 
most sites will see at least MVFR to potentially IFR cigs with the 
passage of the front. VFR cigs may return as early as the late 
morning areas for some terminals, for North Bay terminals. 
Clearing skies will gradually follow for terminals south of 
there, with a slot for clear skies. Models hint at stratus trying to 
reform late Thursday night into Friday morning but confidence was 
too low to add to most terminals. 

Vicinity of SFO...Stratus formed off the west side of the San 
Francisco Peninsula and around KOAK this evening; however, KSFO 
has been lucky with only high clouds being reported. Confidence 
remains low with the stratus forecast here, so opted to remain 
optimistic during the overnight hours. Though lower clouds are 
expected with the passage of the front. We'll be watching the 
frontal passage, which should reach the San Francisco area Thursday 
morning. The best chances for rain look to be between 14-20Z with 
perhaps some vicinity showers or MVFR type cigs lingering into the 
mid afternoon. Winds will be from the south early on and getting to 
about 15kt by the late morning or early afternoon. Flow becomes 
west/northwest once the front passes, with sustained 15kt winds 
through roughly sunset. Cigs should gradually improve with the 
frontal passage as well. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...The HRRR seems to be doing alright this 
morning, capturing the blip of stratus hugging the northern 
portion of the Monterey Bay and slinking into the northern Salinas 
Valley. Models show stratus flirting around KSNS for the next couple 
of hours, with stratus returning after midnight but clearing shortly 
after sunrise. Brought cigs up a bit to MVFR levels rather than 
keeping them at IFR given last nights observations, but the marine 
layer and stratus have humbled us before. Nonetheless, it should be 
short lived as it retreats to the coast during Thursday morning and 
a front slowly meanders southward. VFR cigs are expected by 13-15Z 
Thu, with high clouds returning to the forecast for the afternoon. 
Around or shortly after 0Z Fri, stratus looks to make are return to 
KSNS and KMRY.  

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 850 PM PDT Wed Sep 2 2026

A weak cold front will move through the region late tonight and
into Thursday morning. Winds will continue to shift ahead of its
arrival with gentle to moderate southwest breezes expected. Rain
chances are best north of Pigeon Point during the morning and
early afternoon hours, with isolated showers possible down to
Point Pinos during the afternoon. Northwest winds return behind 
the front and will be gentle to moderate. Diurnal winds increase 
more Friday and Saturday afternoon, especially in vicinity of 
Monterey Bay. The tropical activity well to our south will produce
long period southerly swell beginning Friday and continuing 
through the weekend into the beginning of next week.

&&

.BEACHES...
Issued at 1010 PM PDT Wed Sep 2 2026

A Beach Hazards Statement is in effect Friday-Monday as the swell 
from both Hurricane Marie and Hurricane Karina reaches the coast.
As these hurricane whip up the ocean, the waves travel over 1,000
miles in all directions, gradually flattening out to low 
amplitude, but long period swell. These waves aren't very 
intimidating if you're on a boat in the open ocean, but the long 
period allows them to push much farther up the beach. Long period 
swell always increases the chance for sneaker waves, but that's 
particularly true this weekend since there are 2 different sets of
southerly swell, and their energy will periodically combine. In
addition to sneaker waves, expect strong rip currents and 
breaking waves up to 10 ft. As this is a holiday weekend and the 
weather is otherwise pretty nice, the exposure to the risk is 
high. Avoid the water if you're not an expert swimmer. If caught 
in a rip current, swim parallel to shore until you stop feeling 
the pull. Even on the beach, be prepared for sneaker waves this 
weekend and never turn your back on the ocean.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement from Friday morning through Monday 
     evening for CAZ006-505-509-529-530.

PZ...None.
&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...KR
MARINE...KR

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Prepared by Boulder-Creek.com Weather at: Thu Sep 3 00:30:02 PDT 2026