000
FXUS66 KMTR 130029
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
529 PM PDT Wed Aug 12 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 218 PM PDT Wed Aug 12 2026

 - Near-critical fire weather conditions Wednesday afternoon
   through Thursday early morning across Monterey and San Benito
   Counties due to high based thunderstorms

 - Up to a 15% chance for elevated rain showers/thunderstorms
   Wednesday across the Central Coast

 - Cooling trend through Friday will bring well below normal
   temperatures, gradual warming trend this weekend into next week

 - Minor coastal flooding for bayshore locations along the San Francisco
   Bay, San Pablo Bay, and Monterey Bay through Thursday morning

&&

.SHORT TERM...
Issued at 218 PM PDT Wed Aug 12 2026
(This evening through Thursday night)

Isolated thunderstorm potential continues through this evening along
the Central Coast with increasing confidence compared to this
morning. Radar shows a line of storms developing off of the Big Sur
coastline and moving in to Monterey County. As of this morning/early
afternoon, we have cells moving inland in the vicinity of the Timber
Fire which produced lightning both offshore and on land. This cell
backbuilt to the southwest with additional cells developing in the
wake of the original (inland) cell over the marine environment.
These additional storms have been slowly moving inland in the
vicnity of the Timber Fire and may also become favorable to produce
lightning. Any of these cells will be capable of producing gusty,
erratic wind and dry lightning with any rain evaporating before
reaching the surface due to the elevated storm nature. Fuels are
incredibly dry right now with near critical fire weather concerns
across Monterey and San Benito Counties. If dry lightning occurs, it
is likely to result in additional fire starts. Residents of interior
Monterey and San Benito County (particularly along and within the
higher terrain) should stay weather aware, avoid unnecessary
activities that may result in sparks/fire, and follow guidance from
local officials. Confidence is highest in thunderstorms over the
elevated terrain with orographic lift acting as the trigger for
storms to develop. This is an ongoing event and we will be paying
close attention to the radar this afternoon and evening as it
evolves.

Tonight into tomorrow, a low pressure system offshore will move into
the Central Coast and bring additional chances for thunderstorms
through Thursday morning. HRRR guidance shows several hundred
joules/kg of MUCAPE moving across the Central Coast tonight into
early Thursday with decent upper level support (700-500 mb lapse
rates between 7-8 C/km) and lingering monsoonal moisture. Given that
storms are currently occurring along Big Sur, it is likely that we
will see additional storms again tonight through tomorrow morning
across the Central Coast. Storms tonight and tomorrow morning could
potentially reach as far north as the Santa Cruz Mountains and the
South Bay. Storms are most likely to form along the higher terrain
and be driven by orographic lift.

&&

.LONG TERM...
Issued at 218 PM PDT Wed Aug 12 2026
(Friday through next Tuesday)

Thunderstorm chances diminish after Thursday with drier conditions
to prevail into next week. Temperatures will remain well below
normal across the Bay Area and Central Coast as upper level
troughing persists through this weekend. This will keep highs in the
60s closer to the shoreline and in the 70s to mid 80s across the
interior. The exception will be the interior Central Coast where
highs will warm into the upper 80s to low 90s late weekend into
early next week. Temperatures gradually warm next week as ridging
pushes into the Desert Southwest from the Central US and troughing
continues over the Eastern Pacific Ocean.

&&

.AVIATION...
(00Z TAFS)
Issued at 455 PM PDT Wed Aug 12 2026

Primarily VFR with the marine layer at ~2000ft. Expecting more of
an inland push tonight through Thursday morning. Offshore eddys
will continue to produce some uncertainty in exact timing for the
onset of MVFR/IFR ceilings for the Bay Area terminals.

Vicinity of SFO...As mentioned above, low confidence in timing for
MVFR/IFR ceilings especially at KSFO. There is chance that
MVFR/IFR ceilings develop around sunset tonight at KSFO, though
more likely later during the overnight hours. Higher confidence
for KOAK to get there around sunset.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Onshore push out ahead of weakening
convection already has KSNS in MVFR with KMRY expected to follow
suit over the next couple of hours, then both terminals IFR later
during the overnight hours. There is a slight chance that KMRY
remains MVFR/IFR through the entire forecast period, with KSNS to
lift to VFR by late morning.

&&

.MARINE...
(Tonight through next Monday)
Issued at 455 PM PDT Wed Aug 12 2026

North to northwest fresh to strong winds with isolated near gale
force gusts diminish by Thursday morning. In response, rough seas
subside to moderate by Thursday night. A long period southerly
swell  around 16 to 18 seconds approaches our coastal waters
Friday night  and persists through the weekend. Visibility may
decrease due to  haze and smoke nearby the Big Sur coastline due
to the Timber fire.  Thunderstorms with lightning activity has
been present along the Big  Sur coastline into Monterey Bay as
well with the potential for these  threats to persist into early
Thursday morning.

&&

.FIRE WEATHER...
Issued at 118 AM PDT Wed Aug 12 2026

Near-critical fire weather conditions Wednesday afternoon through
Thursday early morning across Monterey and San Benito Counties due
to high based thunderstorms. Confidence remains low for a low
probability/high impact scenario of elevated rain
showers/thunderstorms across the Central Coast from a low pressure
system that is currently 300 miles southwest of Point Conception.
Erratic/gusty outflow winds of 35-45 mph can be expected with any
elevated rain showers/thunderstorms. Lightning will pose the risk
for new fire starts and has the potential to hinder operations on
the Timber Fire in Big Sur. The areas of most concern will be in the
higher terrain above the marine layer (1,500 feet), namely the Santa
Lucia Mountains and Gabilan Range. Poor minimum daytime relative
humidity around 30% is expected in the afternoons with little-to-no
recovery overnight.

Sarment

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 2 AM PDT Thursday for CAZ006-506-
     508-529-530.

PZ...Small Craft Advisory until 3 PM PDT Thursday for Pt Arena to Pt
     Reyes 10-60 NM.

&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...JM
MARINE...Navarrete

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