FXUS66 KMTR 031848
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1148 AM PDT Thu Sep 3 2026
...New SHORT TERM, LONG TERM...
.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...
(18Z TAFS)
Issued at 1101 AM PDT Thu Sep 3 2026
Inland terminals are mostly VFR with sub-MVFR conditions across the
North Bay and near the coast as a weak frontal boundary approaches
the region. The greatest potential for -RA will be at KSTS this
morning and through early afternoon before the boundary sags
southward throughout the afternoon and early evening. -RA is also
possible at terminals to the south, but little to no mensurable
rainfall is expected south of the Golden Gate. Onshore winds will
increase a bit this afternoon in wake of the frontal passage with
VFR conditions returning. Tonight, the marine layer is forecast to
deepen to around 2000 feet and will see MVFR CIGs along the coast
with the potential for sub-MVFR CIGs early Friday morning. VFR
conditions are anticipated after or around 18Z Friday.
Vicinity of SFO...VFR. Onshore winds are forecast to increase this
afternoon and early evening in wake of the frontal passage with
gusts up to 20 kt. There is the potential for MVFR conditions as the
front passes through between 20Z Thursday-03Z Friday. Winds ease
slightly after sunset. There is greater confidence for MVFR CIGs (40-
60% probability) to develop early Friday morning and persist through
16Z Friday before lifting to VFR. Northwesterly winds once again
increase Friday afternoon.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR. Onshore winds are forecast to increase
this afternoon and early evening. The frontal boundary is forecast
to gradually dissipate as it approaches the region late tonight and
into early Friday morning. As such, expecting MVFR conditions to
develop by late evening and lower to IFR (40-60% probability) into
early Friday morning. There is less than 10-30% chance of reaching
LIFR conditions between 08-15Z Friday, however have left out of the
current TAF package. VFR conditions are anticipated after or around
18Z Friday.
&&
.MARINE...
(Today through Tuesday)
Issued at 1101 AM PDT Thu Sep 3 2026
Rain chances increase over the northern waters through the day as
a weak cold front moves through the region. Southwesterly winds
gradually shift northwesterly by this afternoon after cold frontal
passage. Winds generally stay gentle to moderate but diurnal
fresh to strong gusts return within the Monterey Bay and along the
Big Sur Coast Friday into the weekend. More widespread fresh to
strong gusts return by early next week across the coastal waters.
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 Friday morning through Monday
evening for CAZ006-505-509-529-530.
PZ...Small Craft Advisory until 5 PM PDT this afternoon for SF Bay N
of Bay Bridge.
&&
$$
SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...RGass
MARINE...RGass
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Prepared by Boulder-Creek.com Weather at: Thu Sep 3 12:30:03 PDT 2026
From the National Weather Service
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