FXUS66 KMTR 050758
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1258 AM PDT Sat Sep 5 2026
...New SHORT TERM, LONG TERM...
.KEY MESSAGES...
Updated at 1122 AM PDT Fri Sep 4 2026
- Hazardous conditions at Pacific Coast beaches Friday through
Monday
- 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 1258 AM PDT Sat Sep 5 2026
(Today and tonight)
On Thursday the presence of mid to upper level troughing and a
surface cool front brought many (but not all locations) an early
rain, in some cases an early September daily record breaking rain.
Atypical cool air aloft for early September carried over to Friday
and plenty of cool air aloft is still lingering at this hour early
Saturday morning. With current temperatures broadly in the 50s/60s,
coolest at higher elevations, it's relief e.g. for a time of year
here when it can easily be much warmer at higher elevations in the
lower level temperature inversion under high pressure aloft. Mountain
top air temperatures from Mt St Helena all the way to Chews Ridge
are currently in the lower 50s. Mt Hamilton 30 year early Sep normal
low for example is 62F.
Recently sea surface temperatures in our coastal waters have bumped
upwards to the lower to mid 60s north to south, now 2F to 5F above
Sep normals. This is resulting in a warming effect on nearby coastal
locations where daily minimums are remaining a few to several degrees
warmer than normal. The usual night/morning chill may be noticeably
absent in the last few days.
If you're enjoying the daytime temperatures from the coast to far
inland, daytime highs today will be similar to maybe a few degrees
warmer with 60s/70s coastside/bayside to the upper 70s to lower 80s
inland.
&&
.LONG TERM...
Issued at 1258 AM PDT Sat Sep 5 2026
(Sunday through next Friday)
Forecast daytime highs Sunday will be similar to Saturday's highs,
60s/70s coastside/bayside to the upper 70s to lower 80s inland. Dry
weather will continue Sunday. A weakening or break in mid to upper
level troughing will begin on Labor Day with thermal ridging developing
aloft resulting in a warming trend across the forecast area. This will
result in daytime highs warming back to and slightly above normal e.g.
80s to lower 90s inland to far inland locations.
Global models are still showing redevelopment of 500 mb troughing
over the eastern Pacific during the middle of next week. 00z
guidance however is showing some retrogression of the upper level
trough. This will be at the same time remnant tropical moisture
moves northward and may get entrained into the trough. Our official
forecast shows light rain next week, and it still bears monitoring
however the precipitation forecast over our area has trended drier.
&&
.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...Canepa
LONG TERM....Canepa
AVIATION...KR
MARINE...KR
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Prepared by Boulder-Creek.com Weather at: Sat Sep 5 04:30:03 PDT 2026
From the National Weather Service
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