FXUS66 KMTR 162308
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
408 PM PDT Sun Aug 16 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1222 PM PDT Sun Aug 16 2026

 - Shallower marine layer expected the next few days

 - Minor fluctuations in temperatures this week.

&&

.SHORT TERM...
Issued at 130 PM PDT Sun Aug 16 2026 
(This evening through Monday night)

Water vapor imagery continues to show an upper level trough of 
low pressure off the California Coast and high pressure over the 
Desert Southwest this afternoon. As a result, California remains 
situated between the two, with southwesterly flow aloft. There is
quite a bit of upper level moisture over the ocean moving through
this flow, so expect an increase in high clouds across the region
over the next 24 to 36 hours. Meanwhile, we still have a
relatively deep mariner layer lingering along the immediate coast.
As a result, coastal areas are still running 2 to 3 degrees 
behind temperatures at this point yesterday, but inland areas are
running slightly warmer, given the earlier clearing time. Either
way, most locations across our region are still going to be below
normal or right at normal for this time of year.

The 12z morning KOAK sounding showed the marine layer around 1800
feet deep, and given the observations this afternoon, doubt it 
has compressed much if any today. Therefore, expect another good 
push of low clouds and fog inland this evening and tonight, with
similar clear times and temperatures for tomorrow. Palmer

&&

.LONG TERM...
Issued at 130 PM PDT Sun Aug 16 2026 
(Tuesday through next Saturday)

The main story for this week will be the battle between the 
trough off our coast and the ridge to the southwest, and which one
will influence our forecast the most. At this point in time, the 
models are suggesting that the ridge should be the dominate 
feature for the first part of the work week, with 850 mb 
temperatures climbing approximately a degree or so each day 
through Wednesday, before the influence of the trough takes back 
over for the latter part of the work week and the weekend as it is
forecast to move closer to the coast.

However, this is where things get interesting. There is a lot of 
upper level moisture filtering northeastward in the southwesterly
flow aloft. We are already seeing some thin high clouds 
associated with the leading edge of that moisture, but there is a 
large bulk of that moisture (cloud cover) that is not 
translucent. Therefore, even through the models are suggesting a 
gradual warm up across the inland areas, current thinking is that 
this upper level cloud cover will likely limit day time heating 
and provide a decent insulting blanket at night. And all of this 
said is not taking the marine layer influence into account. 
Therefore, my confidence in an actual "warm up" is not high. In 
fact, my gut says it may likely be dependent on the day, and how 
much sun we actually see. Therefore, expect most places to remain 
at or below normal for the next week, with only minor day to day 
fluctuations possible this week and through next weekend. 

Now, you may have also noted that I said this a lot of this
moisture is not translucent. In fact, current clean IR band shows
what is likely a convective band just south of 25 North and 130
West, so the question is will this moisture get pulled into the 
flow for us? Maybe, but it does not look likely. There is some 
hinting at higher precipitable water values upwards of an 1 inch 
for Thursday and Friday, but any instability with it diminishes as
it gets here. Therefore, expect our predominately dry conditions
to continue across the region.  Palmer

&&

.AVIATION...
(00Z TAFS)
Issued at 408 PM PDT Sun Aug 16 2026

MVFR-IFR stratus lingers across the coastal regions with the rest of 
the region reporting VFR with high-level clouds. Generally IFR 
stratus is expected to develop across the inland regions this 
evening and overnight with some LIFR ceilings possible in favored 
locations, before stratus retreats back to the immediate coastal 
regions through Monday morning. Moderate onshore pattern winds will 
continue through the afternoon and evening hours, turning light 
overnight before resuming Monday afternoon.

Vicinity of SFO... VFR ceilings with high clouds through the evening 
hours with moderate and potentially gusty west-northwest winds. IFR 
stratus will return this evening with low confidence on the exact 
timing, although the model output consensus agree on the stratus 
developing by 09Z. Stratus clears out late Monday morning with 
breezy onshore winds resuming in the afternoon and a moderate 
confidence that stratus returns in the evening before the end of the 
TAF period, with greater confidence in stratus impacts after it ends.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... MVFR-IFR ceilings will persist at MRY 
through the afternoon and evening hours with the stratus deck 
expanding over SNS imminently. LIFR conditions develop overnight 
with stratus clearing at SNS late Monday morning, while confidence 
in a scattering of the ceilings at MRY remaining low to moderate 
during the afternoon and evening hours. Moderate northwest breezes 
persist into the evening hours, with winds turning light overnight 
before the onshore winds resume Monday afternoon.

&&

.MARINE...
(Tonight through next Friday)
Issued at 408 PM PDT Sun Aug 16 2026

Northwesterly breezes persist with localized fresh gusts across
the inner coastal waters. Winds increase to fresh to strong late
Monday and remain elevated through the end of the forecast period.
Seas of around 4 to 5 feet will build to 7 to 8 feet by mid week.
A long period southerly swell around 15 to 17 seconds will
continue to diminish through the early work week.

&&

.FIRE WEATHER...
Issued at 130 PM PDT Sun Aug 16 2026

Expect some nocturnal drying the next few nights as the marine
layer gradually compresses. Therefore, expect more widespread fair
to moderate recoveries developing over the high elevations,
especially in and around the Timber Fire.

&&

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

$$

SHORT TERM...Palmer
LONG TERM....Palmer
AVIATION...DialH
MARINE...Canepa

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Prepared by Boulder-Creek.com Weather at: Sun Aug 16 18:30:03 PDT 2026