FXUS66 KMTR 051140
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
440 AM PDT Sat Sep 5 2026
...New AVIATION, MARINE...
.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...
(12Z TAFS)
Issued at 426 AM PDT Sat Sep 5 2026
Patchy stratus is developing along the SF Bay shoreline while fog
is developing across the North Bay Valleys. Not anticipating
stratus/fog to spread beyond the already impacted airports (STS,
APC, HAF, potentially OAK and SFO). Stratus/fog should dissipate
by late morning (approx. 17/18Z) with VFR persisting through the
remainder of the day. Expecting gustier onshore winds to prevail
again today with the SFO-WMC gradient peaking around +9 mb this
afternoon/evening. Occasional gusts to between 20 to 25 knots are
possible at SFO and SJC this afternoon/evening before winds ease
tonight. The marine layer struggles to redevelop again tonight
which will keep stratus patchier again tonight and see a late
stratus return. Stratus redevelopment becomes more likely closer
to 12Z tomorrow (end of TAF period) but more likely will fall
after 12Z (into the next TAF period).
Vicinity of SFO...Patchy stratus is filling in over the SF Bay and
reaching towards SFO. Guidance indicates some potential for patchy
stratus to fill in over SFO this morning but confidence is mixed
as to if clouds will stay scattered or if a ceiling will develop.
If a ceiling develops it will likely be between 12Z to 16Z. Gusty
onshore winds return this afternoon/evening with gusts to around
25 knots possible. Winds decrease overnight with some potential
for stratus to reach SFO after 12Z tomorrow morning.
SFO Bridge Approach...Generally similar to SFO. Satellite shows
stratus developing over the SF Bay within the SFO Bridge Approach
region. CIGs are likely on the IFR-MVFR border with SFO reporting
scattered clouds at 1100 feet. Stratus will clear by late this
morning with some potential for stratus to redevelop early
tomorrow morning.
Monterey Bay Terminals...VFR expected through late tonight. Breezy
onshore winds develop during the afternoon/evening before winds
ease overnight. Low to moderate confidence that stratus will
redevelop early tomorrow morning given the fact that the marine
layer is struggling to redevelop this weekend. Stratus becomes
more likely closer to 12Z/into the end of the next TAF period.
&&
.MARINE...
(Today through Thursday)
Issued at 426 AM PDT Sat Sep 5 2026
West to northwest breezes will be gentle to moderate through the
beginning of next week. Diurnal moderate to strong breezes are
expected across the San Pablo, San Francisco and Monterey Bays
today into the beginning of next week. Long period southerly swell
will continue to impact the coastal waters through much of the
upcoming week. Fresh to strong gusts become more widespread late
weekend into early next week before winds decrease by midweek.
&&
.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...Kennedy
MARINE...Kennedy
Visit us at www.weather.gov/sanfrancisco
Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea
Prepared by Boulder-Creek.com Weather at: Sat Sep 5 12:30:03 PDT 2026
From the National Weather Service
|