FXUS66 KMTR 131827
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1127 AM PDT Thu Aug 13 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 730 AM PDT Thu Aug 13 2026
- Elevated fire weather conditions through Thursday for low
relative humidity in the higher terrain
- Cooling trend through Friday will bring well below normal
temperatures, gradual warming trend through the weekend and
into next week
&&
.UPDATE...
Issued at 730 AM PDT Thu Aug 13 2026
The high-based convective threat continues to diminish across the
Central Coast. However, there still is a non-zero chance. Thus, will
remove from Key Messages and will remove the Fire Weather section of
the AFD. However, low humidities in the higher terrain will result
in an elevated fire weather threat through the day. No other major
adjustments needed this morning as the forecast remains on track.
RGass
&&
.SHORT TERM...
Issued at 1225 AM PDT Thu Aug 13 2026
(Today and tonight)
The upper-level low remains off Point Conception and will continue
to bring up to a 15% chance for elevated rain showers/thunderstorms
through early Thursday morning across the Central Coast as it moves
inland. This will bring near-critical fire weather conditions
through Thursday early morning across Monterey and San Benito
Counties. Erratic/gusty outflow winds up to 40 mph can be expected
with any elevated rain showers/thunderstorms. The main concern is
lightning which will pose the risk for new fire starts and has the
potential to hinder operations on the Timber Fire. Smoke from the
Timber Fire will continue to be transported into the Central Coast
via light southwesterly winds. Smoke will get trapped under the
inversion at night/in the morning, making the appearance and smell
worse. The proximity to the low will allow for a relatively deeper
marine layer across the Central Coast (2,000 feet) than the Bay Area
(1,800 feet). Sensible weather wise, the cooling and moistening
trend will continue through Friday with temperatures well below
normal.
&&
.LONG TERM...
Issued at 1225 AM PDT Thu Aug 13 2026
(Friday through Wednesday)
Friday will see the coolest conditions of the week with well below
normal temperatures and a deep marine layer as upper-level troughing
persists across the West Coast. By the weekend, upper-level ridging
will build in to the Desert Southwest and an upper-level low will
develop well off the West Coast. This will lead to cooler conditions
with a deeper marine layer in the Bay Area and hotter conditions
with a more compressed marine layer for the Central Coast.
Temperatures will remain below normal with the higher terrain
moderating to near normal with the help of warming 850 mb
temperatures.
&&
.AVIATION...
(18Z TAFS)
Issued at 1127 AM PDT Thu Aug 13 2026
The marine layer was 2200 feet deep this morning and it is set to
increase up to 2500 feet tonight. As a result, stratus is taking a
bit longer to scatter out of the remaining terminals, though
widespread VFR should prevail after noon. The only exception is HAF
where they will maintain MVFR ceilings through the day with
occasional misty conditions that may impact visibility. Gusty
onshore winds increase through the afternoon with possible gusts
around 20 to 25 kt. Breezes become light overnight, generally from
the west to southwest. A deepening marine layer may initiate an
early onset of stratus this TAF period. Coastal terminals will
develop MVFR ceilings this afternoon. Inland sites develop MVFR
ceilings around midnight. Stratus should scatter out mid to late
morning Friday.
Vicinity of SFO...Gusty west to southwest winds prevail through the
afternoon and ease around sunset. Higher chance for gusts in excess
of 22 kt at SFO than OAK. MVFR ceilings make an early return tonight
with medium confidence on the exact timing. Given the expected
marine layer depth, stratus is expected to clear later tomorrow
around 19-20Z.
SFO Bridge Approach...Similar to SFO. Stratus should generally
develop after and clear before SFO.
Monterey Bay Terminals...Onshore winds with gusts around 20 kt
increase this afternoon, shortly after the remaining stratus clears
from the terminals. Relied on persistence for MVFR stratus arrival
today, so expect ceilings to develop this afternoon. Onshore winds
remain light overnight with potential for ceilings to become low-end
MVFR. Medium to high confidence that they will remain MVFR through
the TAF period.
&&
.MARINE...
(Today through Tuesday)
Issued at 1127 AM PDT Thu Aug 13 2026
Moderate north to northwest winds prevail through the day and into
the weekend with moderate seas around 5 to 8 feet. A long period
southerly swell around 16 to 18 seconds is set to approach our
coastal waters by Friday evening and persist through the weekend.
Haze and smoke may decrease visibility nearby the Big Sur
coastline due to the ongoing Timber fire.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 PM PDT this afternoon for Pt Arena
to Pt Reyes 10-60 NM.
&&
$$
SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Navarrete
MARINE...Navarrete
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Prepared by Boulder-Creek.com Weather at: Thu Aug 13 12:30:02 PDT 2026
From the National Weather Service
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