FXUS66 KMTR 050009
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
509 PM PDT Fri Sep 4 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1122 AM PDT Fri Sep 4 2026

 - Hazardous conditions at Pacific Coast beaches Friday through
   Monday

 - Minor coastal flooding during high tide for bayshore locations
   along the San Pablo Bay Friday afternoon/evening

 - Below normal temperatures through the weekend, gradual warming
   and drying trend kicks off Monday

 - Remnant tropical moisture likely Tuesday through Thursday

&&

.SHORT TERM...
Issued at 1122 AM PDT Fri Sep 4 2026
(Friday through Monday)

The primary concern over the Labor Day holiday weekend is hazardous 
conditions at Pacific Coast beaches Friday through Monday. Two sets 
of long period southerly swell from distant Hurricane Karina and 
Hurricane Marie will result in an increased risk for sneaker waves 
and strong rip currents with breaking waves up to 10 feet. Remaining 
out of the water will not be enough, you will need to stay off of 
beaches, jetties, and rocks to avoid being swept into the ocean by a 
sneaker wave. Blue sky days are the most deadly at area beaches, 
don't further the narrative. Minor coastal flooding is expected 
during high tide for bayshore locations along the San Pablo Bay 
Friday afternoon/evening. Impacts can be expected primarily in 
bayside Marin County. Sensible weather wise, anomalously deep upper-
level troughing will maintain below normal temperatures and onshore 
flow through Sunday. The marine layer will likely be extremely 
nuanced, especially today into tomorrow, as it has to form from 
scratch after being mixed out by the front. Generally speaking, it 
should be on the deeper side with the associated lift. In the 
interim, ample low-level moisture and clear skies will make patchy 
fog possible in the mornings. Gradual warming and drying trend kicks 
off Monday as the low begins to fill and move east.

&&

.LONG TERM...
Issued at 1122 AM PDT Fri Sep 4 2026
(Tuesday through Thursday)

Upper-level ridging will nose in from the east on Tuesday, likely 
bringing the warmest day of the week with temperatures rebounding to 
near normal. A reinforcing trough is expected to dig well off the 
West Coast and pickup what will likely be Tropical Depression Marie 
Tuesday into Wednesday. This will turn the upper-level pattern into 
a conveyor belt of moisture with cyclonic flow to the west and anti-
cyclonic flow to the east. As we are dealing with two moving 
targets, the low and Marie, uncertainty is relatively high. It's 
important to note that Marie will not be making landfall in 
California, let alone will it be tropical by the time it gets here. 
We are simply going to get remnant moisture from it. The official 
forecast has widespread rainfall up to 0.25" with locally higher 
amounts up to 0.50" in the higher terrain. Right now, this looks 
like a beneficial event with limited instability.

&&

.AVIATION...
(00Z TAFS)
Issued at 509 PM PDT Fri Sep 4 2026
Cumulus clouds pepper areas of higher terrain in the North Bay, 
Central Coast, and Diablo Range, while clear skies prevail 
elsewhere. VFR conditions are expected to prevail through the 
evening, with the forecast becoming a bit more tricky for later 
tonight and into Saturday morning. The highest confidence for 
stratus and patchy fog development will be for North Bay terminals, 
where lingering moisture from the rain would promote radiation 
fog/stratus. Around the Bay Area, some guidance tries to show it 
develop around KOAK and KSFO while other inland terminals remain 
VFR. Any low cloud and fog that develops should be short lived, 
mixing out a few hours after sunrise. VFR conditions are expected to 
prevail after that. Medium to high confidence in the forecast.

Vicinity of SFO...Observations and webcams show a few cumulus clouds 
off in the distance, with VFR conditions being reported. Breezy 
onshore winds will hold through roughly sunset, with sustained 
speeds around 15kt. Wind ease as we head into the overnight hours, 
with the next forecast challenge being whether or not KSFO gets 
stratus tonight. Some hi-res guidance, such as the HRRR and the 
HREF, show a60-70% chance of development on the west and north side 
of the San Mateo Peninsula/San Bruno Gap. Opted to keep SCT MVFR 
cigs in the TAF tonight as a result, with low clouds eroding by 
mid to late morning. Some mid level clouds may return for the 
afternoon and evening, which will be accompanied with another 
round of breezy onshore winds. Medium confidence in the stratus 
forecast, high confidence in the wind forecast. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...The toughest forecast might be around the 
Monterey Bay tonight, though the question is will the marine layer 
return? Confidence is low to medium for the terminals in this area, 
as hi-res models keep us VFR all night, while MOS, GFSLAMP, and the 
NBM want to sock us in with stratus. Opted to keep the IFR cigs for 
tonight, but if data continues to trend clear, will start improving 
cigs for the overnight and morning hours.  

&&

.MARINE...
(Tonight through next Thursday)
Issued at 509 PM PDT Fri Sep 4 2026

West to northwest breezes will be gentle to moderate through the
weekend into the beginning of next week. There will be
occasionally moderate to strong breezes across the San Pablo, San
Francisco and Monterey Bays by the end of the weekend into the
beginning of next week. Long period southerly swell has arrived
with the Point Sur Buoy registering 18 second period early this
afternoon out of the SSW. The long period southerly swell will
continue 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 through Monday evening for CAZ006-505-
     509-529-530.

     Coastal Flood Advisory until 9 PM PDT this evening for CAZ506.

PZ...Small Craft Advisory until 9 PM PDT this evening for Mry Bay.

     Small Craft Advisory from 9 AM to 9 PM PDT Sunday for Mry Bay.

     Small Craft Advisory from 9 AM Sunday to 3 AM PDT Monday for 
     Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras 
     Blancas 0-10 nm.

&&

$$

SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...KR
MARINE...JM

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Prepared by Boulder-Creek.com Weather at: Fri Sep 4 20:30:03 PDT 2026