Technical NOAA Weather Discussion

FXUS66 KMTR 040514
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1014 PM PDT Thu Sep 3 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1147 AM PDT Thu Sep 3 2026

 - Well below normal temperatures with beneficial rain Thursday

 - Hazardous beach conditions at Pacific Coast beaches Friday
   through Monday

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

&&

.SHORT TERM...
Issued at 1147 AM PDT Thu Sep 3 2026
(Thursday through Thursday night)

Cloud cover will increase through the day as a cold front approaches 
from the northwest. FROPA will occur this afternoon into this 
evening from northwest to southeast. The standard wind shift from 
southeasterly to northwesterly will occur pre and post-frontal, 
respectively, with gusts up to 25 mph to be expected. Gusts of 30-40 
mph are expected through terrain favored gaps and passes such as The 
Delta, Altamont Pass, and Pacheco Pass, as well as down the Salinas 
Valley. For the North Bay, rainfall totals up to 0.25" with locally 
higher amounts up to 0.75" in the higher terrain are expected. South 
of the Golden Gate Bridge, less than 0.10" is expected with 
accumulation favoring the coast and higher terrain with the help of 
orographic lift. Overperformance is still a possibility with the 
struggles of guidance/models in the early season. While rainfall is 
expected to be beneficial, wet roadways will create slick driving 
conditions and increase stopping distance. With ample low-level 
moisture and post-frontal clearing, the marine layer will try to 
reform tonight. As a result, patchy fog/stratus will be possible for 
the Friday morning commute.

&&

.LONG TERM...
Issued at 1147 AM PDT Thu Sep 3 2026
(Friday through Wednesday)

The most impactful weather phenomenon Friday through Monday will be 
hazardous conditions at Pacific Coast beaches. 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. With pleasant 
sensible weather expected, these are the type of days that are most 
deadly; with it being the Labor Day holiday weekend, that will 
likely only make matters worse. If you want an outdoor activity this 
weekend, hit the trails instead of the beach. There's good agreement 
through the weekend that there will be an upper-level low over the 
Pacific Northwest which will keep our region under the influence of 
troughing. As such, expect below normal temperatures and onshore 
flow to continue with the return of the marine layer. The forecast 
is now dry this weekend with the farther west track of Marie and dry 
air filtering in from the northwest. Uncertainty arrives Monday in 
terms of low versus trough, but global ensemble clusters are in 
agreement that the pattern becomes progressive again as the low 
begins to fill and move east. This will allow for ridging to build 
in from the Desert Southwest, kicking off the gradual warming and 
drying trend. It is now looking likely that at least some of Marie's 
remnant moisture will eventually be brought into our area as soon as 
Tuesday. Whether this transpires as clouds or rainfall will be 
dependent on the reinforcing low/trough and the strength of the 
flanking ridges. Right now, the official forecast has light rainfall 
Tuesday through Thursday favoring the Central Coast.

&&

.AVIATION...
(06Z TAFS)
Issued at 1014 PM PDT Thu Sep 3 2026

The front is working its way through the Bay Area and into the 
Central Coast, with light rain being reported at the terminals 
around San Francisco. North Bay counties have dried out, leaving 
behind it clearing skies and mainly VFR conditions. The question for 
tonight will be, do we continue to clear or will be get some pockets 
of sunrise stratus and fog after the front passes? The latest 
guidance leans towards the latter with stratus and fog developing 
around sunrise and eroding a few hours after that. VFR conditions
then look to prevail through the forecast period. Medium 
confidence in the forecast. 

Vicinity of SFO...The front is here while writing the AFD and light 
rain is being observed around the San Francisco Bay terminals along 
with MVFR cigs. Expect these conditions to linger through the next 
few hours, with rain chances diminishing as the front moves south. 
The question for these KSFO and KOAK will be, does the stratus last. 
Guidance seems to be the most bullish here with cigs flirting around 
SF Bay. Opted keep the pessimistic forecast in, though it might be 
more of a TEMPO situation or just outside of the range rings. 
Conditions for sure look to improve around and after sunrise, with 
VFR conditions prevailing during the day. Onshore winds pick up mid 
to late afternoon, with sustained speeds around 12-15kt and gusts up 
to 22-25kt through sunset. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Low clouds are lingering around Monterey 
Bay, with high clouds passing overhead as the front arrives. Lower 
clouds should make it to KMRY and KSNS later tonight, with perhaps 
even some VCSH or -SHRA for a few hours seeing how well the cold 
front has held up. MVFR to potentially IFR cigs will be possible as 
the front passes through, with conditions gradually improving behind 
it. 

&&

.MARINE...
(Tonight through next Wednesday)
Issued at 1014 PM PDT Thu Sep 3 2026

Rain chances will continue to diminish tonight, with gentle to
moderate northwesterly breezes expected in wake of the frontal
passage. Diurnal fresh to strong gusts return within the Monterey
Bay, the Big Sur Coast, and near Point Reyes Friday into the
weekend. Widespread fresh to strong gusts return by early next
week across the coastal waters, decreasing to moderate to fresh
breezes by midweek. Long period southerly swell associated with
tropical activity well to our south will reach the coastal waters
Friday and continue into early 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 6 AM PDT Friday through Monday 
     evening for CAZ006-505-509-529-530.

PZ...None.
&&

$$

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

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Prepared by Boulder-Creek.com Weather at: Thu Sep 3 22:30:03 PDT 2026
From the National Weather Service