FXUS66 KMTR 191147
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
447 AM PDT Wed Aug 19 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1201 AM PDT Wed Aug 19 2026

 - Compressed marine layer today, increases Thursday into the 
   weekend

 - Near normal temperatures today followed by a gradual cooling
   into the weekend

 - Elevations above about 1000 feet will have warm temperatures
   and RH values in the teens this morning into the afternoon

&&

.SHORT TERM...
Issued at 1201 AM PDT Wed Aug 19 2026
(Today and tonight)

A slightly more shallow marine layer tonight resulted in a somewhat 
later onset of stratus pushing inland with less extensive coverage 
than what was seen last night into early Tuesday morning. Another 
mild overnight into early this morning should result in stratus 
retreating back to the coast an hour or two sooner than we generally 
see this time of year. Todays warmup will barely be noticeable for 
areas below 1000ft away from the coast, with temperatures at higher 
elevations across the East Bay Hills and Santa Lucias including Big 
Sur and the Timber fire, running 10 degrees or more above normal. 
MinRH values will be in the teens this afternoon across those 
elevated locations, fortunately light winds continue to be a 
mitigating factor. The weak fetch of offshore flow above the marine 
layer over the southern Central Coast will shift late tonight with 
improved RH recovery expected into early Thursday, along with an 
increase in the marine layer depth.

&&

.LONG TERM...
Issued at 1201 AM PDT Wed Aug 19 2026
(Thursday through Tuesday)

Troughing persists through the extended forecast with gradually 
cooling setting in on Thursday and continuing through the weekend 
into next week. The persistent ridging to our east increases to near 
600dm by the middle of next week, while continuing steer at least a 
couple of tropical waves around its perimeter well to our south. The 
potential tropical system still depicted beyond the official 
forecast period still appears to offer little impact for our area 
while we will continue to monitor any mid-level moisture advection.

&&

.AVIATION...
(12Z TAFS)
Issued at 440 AM PDT Wed Aug 19 2026

Mix of IFR-LIFR conditions across the board with only LVK staying
VFR. Stratus remains in place through late this morning before
clearing during the afternoon/evening. Moderate confidence on
timing of stratus return tonight with the marine layer remaining
compressed around 1000 ft. Used a mix of persistence and ensemble
guidance for the TAFs with stratus roughly arriving around 06-09Z
across the interior and 00-03Z along the coast. With the marine
layer compressing, it is questionable if SJC and LVK will see a
return of stratus tonight but chances start to increase after 09Z.
Diurnally breezy onshore winds return this afternoon and evening
before weakening overnight.

Vicinity of SFO...IFR conditions prevail through late morning
before gradually improving to VFR by the early afternoon. Breezy
onshore winds expected during the afternoon/evening with gusts
peaking between 20 to 25 knots. Low to moderate confidence in
stratus return tonight with some models suggesting stratus stays
confined over OAK and does not fill in towards SFO over the bay.
Opted for stratus returning around 07Z tonight due to persistence
and lamp guidance but this will need to be watched closely.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR conditions continue through late
morning when stratus gradually starts to rise and VFR briefly
returns this afternoon/evening. Model guidance is pushing for a
later return of stratus (after 03Z) but this seems unlikely, even
with the marine layer compressing slightly. Kept stratus returning
closer to 01Z for MRY and closer to 03Z for SNS which matches 
better with persistence. IFR to LIFR conditions then persist
through the remainder of the TAF period.

&&

.MARINE...
(Today through Monday)
Issued at 440 AM PDT Wed Aug 19 2026

Locally strong northwesterly breezes across the northern outer
waters and along the coastal jet regions will bring hazardous
conditions for small craft periodically through the weekend.
Breezy fresh winds are expected across the San Pablo Bay and the
San Francisco Bay with locally stronger gusts possible where
terrain promotes wind funneling. Rough seas in the outer waters
will abate Thursday with moderate seas prevailing by Friday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 3 AM PDT 
     Thursday for Pt Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory from 3 PM this afternoon to 3 PM PDT 
     Thursday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

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

&&

$$

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

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Prepared by Boulder-Creek.com Weather at: Wed Aug 19 06:30:02 PDT 2026