FXUS66 KMTR 050511
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1011 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...
(06Z TAFS)
Issued at 1010 PM PDT Fri Sep 4 2026
Little change to the forecast this evening as VFR conditions prevail
for the time being. Satellite shows some patchy stratus and/or fog
developing around Marin County and San Mateo County, with mainly
clear skies elsewhere. The forecast remains a bit tricky for later
tonight and into Saturday morning. The highest confidence for
stratus and patchy fog development remains across the 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...Clear skies are being observed around most of KSFO
this evening, with a few clouds just now popping up around the San
Bruno area. The question remains, does KSFO gets stratus tonight?
Some hi-res guidance, such as the HRRR and the HREF, now show a 40-
60% 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 to high 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? Do we get radiational cooling to promote some stratus
development. 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 start
lifting/improving the cigs given hi-res guidance has backed off on
srrtatus development.
&&
.MARINE...
(Tonight through next Thursday)
Issued at 1010 PM PDT Fri Sep 4 2026
West to northwest breezes will be gentle to moderate through 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.
PZ...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...KR
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Prepared by Boulder-Creek.com Weather at: Sat Sep 5 00:30:02 PDT 2026
From the National Weather Service
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