573
FXUS66 KMTR 211820
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1120 AM PDT Sat Sep 21 2024

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 315 AM PDT Sat Sep 21 2024

Gradual warming continues this afternoon, though todays highs will
still be at or slightly below normal for most locations across our
area. The potential for moderate HeatRisk Monday and Tuesday remains
in the forecast.

&&

.UPDATE...
Issued at 845 AM PDT Sat Sep 21 2024

Stratus extends across most of the region`s valleys, mixing out
through the morning inland with patchy clouds remaining at the
immediate coast. Latest observations from the Fort Ord profiler
suggest that the marine layer is gradually compressing as high
pressure builds over the region, with the last report suggesting
a marine layer around 1600 feet. A warming trend is still expected
through the day, but the 24 hour trends are lagging behind. Not
enough confidence to update the forecast at this time, but will
continue to monitor the trends through the afternoon to see if we
need to bump down temperatures for the second day in a row.

DialH

&&

.SHORT TERM...
(Today and tonight)
Issued at 315 AM PDT Sat Sep 21 2024

High pressure expanding across our area today and tomorrow will
result in quiet weather with gradual warming today and tomorrow.
Marine boundary layer (re: Ft Ord profiler) was steady at around 2k
ft yesterday, with similar low level onshore flow persisting today.
Low level stratus will clear farther inland by mid morning over the
Bay Area and late morning around gaps and valleys around Monterey
Bay. Some low stratus will linger over coastal communities this
afternoon, but will see more of a mix of sun and clouds than what
was realized on Friday. This will help temps near the coastline get
in on the gradual warming that will occur farther inland. Tomorrow
will be similar, just a few degrees warmer as H50 heights continue
to slightly increase.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 315 AM PDT Sat Sep 21 2024

A weak upper level low begins to develop over the California Central
Coast tomorrow interrupting the expanding area of high pressure to
our west over open water. Deterministic guidance is in a little
better agreement with the evolution of the upper level disturbance
than in previous runs. The weak closed low wanders southward
Monday, lifting back to the north offshore of our area on Tuesday,
and then farther north to be absorbed by the Polar Jet on
Wednesday. The net result appears to be less impactful heat event
for Monday and Tuesday than previously thought, though moderate
HeatRisk remains a possibility for many interior locations for
both Monday and Tuesday. Persistent, offshore upper level
troughing for the second half of next week will help cool daytime
temps back to around seasonal averages for Wednesday and beyond.

&&

.AVIATION...
(18Z TAFS)
Issued at 1119 AM PDT Sat Sep 21 2024

Stratus has cleared from most area terminals this morning, leaving
behind VFR in its wake. VFR will persist through the early evening
today with W/NW breezy winds at area terminals this afternoon.
Stratus begins to return in the early portion of the evening for
Monterey Bay tonight, but later for most other terminals. However,
stratus is likely to bring IFR CIGs overnight for the majority of
terminals. Late morning clearing to VFR on Sunday expected.

Vicinity of SFO...VFR lasts through the early morning of Sunday,
though confidence on this is only moderate. Some models indicate a
return of stratus prior to midnight, though at this time, higher
confidence is placed in stratus bringing MVFR CIGs beyond midnight
for KSFO. Otherwise, breezy NW winds return this afternoon, but
settle and become light into the late evening.

SFO Bridge Approach...Clear through the day today. Low coastal
clouds are likely to filter into the SF Bay overnight bringing low
CIGs.

Monterey Bay Terminals...IFR CIGs are expected to clear soon, with
VFR lasting through the late afternoon today. Stratus will make an
early return, bringing IFR CIGs once more towards the 00-02Z Sunday
window. In the overnight, CIGs are expected to lower to become LIFR,
with some reduction in visibility as fog develops.

&&

.MARINE...
(Today through Thursday)
Issued at 1119 AM PDT Sat Sep 21 2024

Fresh to moderate northwest winds continue, with strong gusts over
the far northern outer waters through Monday. Seas will be
moderate, continuing to build and remain rough in the outer
waters with significant wave heights up to 12 feet. Winds
decrease and seas abate beginning Tuesday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Monday for Pt Arena to Pt
     Reyes 10-60 NM.

&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...AC
MARINE...AC

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea