406
FXUS66 KMTR 280122
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
622 PM PDT Wed Aug 27 2025

...New UPDATE...

.KEY MESSAGES...
Updated at 1251 PM PDT Wed Aug 27 2025

 - Temperatures hover near normal through Friday, to slightly above
   normal through the weekend.

 - Quiet weather through the weekend, into beginning of next week.

&&

.UPDATE...
Issued at 609 PM PDT Wed Aug 27 2025

That`s it, our chances of convection are over. The 00Z balloon
just popped and reported much drier air below 700 mb. The PW
dropped from 1.00" at 12Z to 0.69" at 00Z. This brought the MUCAPE
down to a paltry 17 J/kg, with an insurmountable -658 J/kg of CIN.
After nearly 5 days of slim chances for thunderstorms, I am
officially downgrading to zero chance going forward.

While the monsoon moisture has filtered out, there is another
push of moisture moving into southern California tomorrow from the
remnants of Tropical Storm Juliette. This will bring some rain to
San Diego, but there is high confidence that we won`t see any
impact from this moisture. A developing short wave trough will
move quickly through the pattern and drag the vast majority of
the tropical air mass east into the desert. The confidence is so
high that the moisture won`t make it to the Bay Area that I cant
find any guidance that even brings us high clouds.

Finally, the stratus bank has again pulled nearly 100 miles off
the coast this afternoon. This happened yesterday and it took much
longer for marine layer clouds to redevelop over land, if they
ever did. SFO never actually reported a ceiling this morning despite
all model guidance to the contrary. As such, expect similar
delayed clouds returning overnight. Another good evening for
stargazers.

&&

.SHORT TERM...
Issued at 1251 PM PDT Wed Aug 27 2025
(This evening through Thursday)

Quiet weather for the rest of today and into tomorrow as an upper
level low sits off the coast of central and southern CA. This
evening and into tonight, stratus will slowly saunter into the
region with skies clearing by mid to late Thursday morning. Upper
level ridging from the Desert Southwest tries to nose into northern
CA, which should lead to slight increase in high temperatures for
tomorrow.

&&

.LONG TERM...
Issued at 1251 PM PDT Wed Aug 27 2025
(Thursday night through next Tuesday)

Quiet weather will continue into the extended portion of the
forecast as we are caught between upper level troughing over the
eastern Pacific and upper level ridging to our east. Flow looks to
remain zonal or quasi zonal at times, with the main differences
being the temperature. A gradual uptick in high temperatures is
expected Friday and into the weekend, with temperatures faltering
some into early next week. The marine layer has shown some signs of
compressing, which means the stratus may not be as widespread over
the weekend.

&&

.AVIATION...
(00Z TAFS)
Issued at 442 PM PDT Wed Aug 27 2025

Adjusted the timing of stratus return tonight to push it back closer
to 09-12Z timeframe. Satellite imagery shows stratus approximately
100 miles offshore which is approximately the same as where it was
at this time yesterday. Models are continuing to show stratus along
the coastline with early arrivals of stratus favored by the NAM.
Leaning towards guidance from the HRRR and the MOS which both
favored RH increasing late tonight and stratus returning early
tomorrow morning. Low to moderate confidence in timing of stratus
return, will keep an eye on satellite and adjust TAFs as needed if
stratus builds faster than anticipated. CIGs will be on the IFR-MVFR
border overnight and will clear by mid to late morning.

Vicinity of SFO...Pushed stratus arrival back to 10Z with the
current setup supporting a later return of stratus. Confidence is
low to moderate that stratus will reach SFO with most ensemble
guidance showing this scenario. The NAM again favors stratus
reaching easternmost portions of the SF Bay and OAK but not
extending across the bay and reaching OAK. Confidence in the NAM is
mixed at the moment given it tends to overdue moisture and is the
primary model leaning towards an early stratus return over a later
one. It did, however, adequately show stratus not reaching SFO last
night while other models did show stratus reaching SFO. For now,
continuing to show a late arrival of stratus but will continue to
monitor and adjust as new data comes in.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...IFR-MVFR CIGs expected overnight. Pushed
stratus arrival back to around 09Z given the lack of offshore
stratus and models overdoing the amount of current offshore stratus.
Moderate confidence in timing but will keep an eye on it and adjust
as new data comes in. Breezy onshore winds each afternoon/evening
before diminishing and becoming locally variable overnight.&&

.MARINE...
(Tonight through next Monday)
Issued at 442 PM PDT Wed Aug 27 2025

Expect light to moderate winds and seas to continue across the
coastal waters through late week. Winds will increase with fresh
to strong gusts and seas will build over the weekend causing
hazardous conditions for the outer waters into the next work week.

&&

.MARINE...
(Tonight through next Monday)
Issued at 442 PM PDT Wed Aug 27 2025

Expect light to moderate winds and seas to continue across the
coastal waters through late week. Winds will increase with fresh
to strong gusts and seas will build over the weekend causing
hazardous conditions for the outer waters into the next work week.

&&

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

$$

SHORT TERM...KR
LONG TERM....KR
AVIATION...Kennedy
MARINE...Murdock

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