557
FXUS66 KMTR 132325
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
425 PM PDT Thu Aug 13 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1228 PM PDT Thu Aug 13 2026

 - Cooling trend through Friday will bring well below normal
   temperatures

 - Subtle warming trend into next week, yet temperatures are
   forecast to remain below normal

&&

.SHORT TERM...
Issued at 1228 PM PDT Thu Aug 13 2026
(This evening through Friday night)

A mid/upper level trough of low pressure remains off of the West
Coast and is resulting in widespread cooler temperatures this
afternoon, as much as 15 deg F below normal. Humidities across the
region have also improved, especially beneath the approximately
2,200 foot marine layer. The potential for high-based convection
has also greatly diminish as the higher PWAT values and
insatiability continue to shift eastward as a result of the
troughing of of the coast. Low clouds are highly likely to return
to the coast this evening and spread into the interior valleys
early Friday morning. Have also added patchy drizzle to favored
locations as the marine layer is forecast to deepen to around
2,500 feet overnight. On Friday, expecting a slower stratus
retreat to the coastline with similar or slightly cooler
temperatures than today. Friday night into Saturday morning,
expecting another around of widespread drizzle along the coast and
in the favored upslope regions.

&&

.LONG TERM...
Issued at 1228 PM PDT Thu Aug 13 2026
(Saturday through next Wednesday)

A subtle warming trend is forecast to begin by Saturday
afternoon, yet temperatures will remain below seasonal averages
into much of next week. This is as the trough off of the West
Coast weakens and the ridge begins to build over the Desert
Southwest. As a result, the marine layer is forecast to compress
with more typical late morning to early afternoon retreat of
stratus to the coastline.

&&

.AVIATION...
(00Z TAFS)
Issued at 425 PM PDT Thu Aug 13 2026

MVFR stratus lingers across the coastal regions, particularly in
Marin County and the Monterey Bay region, with only limited clearing
expected for the rest of the day. Breezy and gusty southwest winds
will continue through the evening hours across the terminals.
Widespread MVFR stratus is expected to flow into the inland valleys
through the evening and overnight hours, with some IFR stratus
possible in favored areas. Stratus is not expected to dissipate
until early Friday afternoon, around 19-21Z for most terminals. Low
to moderate confidence that more northwesterly flow will develop
Friday afternoon and evening.

Vicinity of SFO... Wave clouds off the crest of the San Mateo
coastal ranges may create transient periods of MVFR ceilings at the
terminal through the evening, otherwise VFR conditions continue with
moderate and gusty west-southwest breezes. More widespread MVFR
ceilings arrive this evening and persist into the early afternoon on
Friday. Low to moderate confidence that winds will turn more towards
the west or west-northwest on Friday afternoon and evening, with
moderate confidence in stratus returning to the terminal sometime
Friday evening to Friday night, although confidence in timing is low.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... MVFR conditions persist through the
evening and overnight hours with some IFR ceilings possible
overnight. Moderate and gusty onshore flow with a southwest
component continues into the evening hours, diminishing overnight
before a moderate confidence forecast for more northwesterly flow
develops Friday afternoon. Low confidence in a brief scattering out
of the stratus clouds Friday afternoon a couple of hours before the
end of the TAF period.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 425 PM PDT Thu Aug 13 2026

Gentle to moderate west-northwest winds persist into the weekend
and  early next week as seas continue to subside to moderate in
response.  A long period southerly swell of about 16 to 18 seconds
approaches  our coast Friday night into Sunday. Light drizzle is
possible across  the coastal waters. Haze and smoke may also
impact visibility along  the Big Sur coastline due to the Timber
fire.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...DialH
MARINE...Navarrete

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