982
FXUS66 KMTR 160516
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1016 PM PDT Sun Sep 15 2024

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 112 PM PDT Sun Sep 15 2024

Gusty winds continue today, with chances of drizzle and light rain
arriving later tonight into Monday afternoon. Temperatures below
seasonal averages continue through midweek with a second upper level
low moving in, then gradual warming into the next weekend.

&&

.UPDATE...
Issued at 857 PM PDT Sun Sep 15 2024

The cold front is finishing its trip across the CWA this evening
leaving behind strong NW wind (gale force at Altamont Pass), cool
air, and a complex mix of cloud layers. There are a few weak
returns on the lowest scan of the radar, but most of the moisture
is above 6,000 m and evaporating/subliming in the deep dry layer
before it reaches the ground. Nevertheless we have received
reports of a few rain drops hitting the sidewalk or windshield on
social media. The better chance for rain comes tomorrow as the air
aloft continues to cool and the instability increases.

&&

.SHORT TERM...
(This evening through Monday)
Issued at 112 PM PDT Sun Sep 15 2024

The weather pattern today is dominated by a cold front working
through the Bay Area and into the Central Coast. The cold front has
brought noticeable cooler temperatures across the board, with highs
reaching the low to mid 70s in the inland valleys, the upper 70s to
low 80s in the North Bay valleys and southern Monterey County, the
mid to upper 60s in the Bayshore, and the upper 50s to mid 60s along
the Pacific coast. Monday is set to be even cooler inland, with even
the North Bay valleys and southern Monterey County seeing
temperatures in the low to mid 70s.

Northwest winds should continue to build through the day, with the
strongest gusts tonight into early Monday morning before winds
diminish later in the morning through the afternoon. The strongest
gusts will be through the gaps, passes, and favorably oriented
(northwest-southeast) valleys and coastal regions (e.g. the Salinas
Valley, the San Bruno Gap, the Sonoma Coast, and the Santa Cruz
County coast west of Capitola). These areas will see gusts up to 35-
40 mph, occasionally 45-50 mph. The rest of the region should see
gusts of 25-35 mph.

Chances of drizzle and light rain arrive late tonight into Monday
afternoon, but accumulations are expected to be pretty light. The
higher elevations are expected to see a tenth to a quarter of an
inch of rain, with some isolated areas seeing nearly half an inch.
The forecast for the lower elevations continues to be even lighter,
with a tenth of an inch being the absolute maximum and the North Bay
and southern Monterey County largely missing out.

Low clouds continue to linger across the San Francisco Bay Area and
the southern Monterey Bay. Some clearing is possible through the
afternoon, but the cooler temperatures could keep stratus around at
the immediate coast and some of the higher elevations. Tonight, the
strong winds and rain make for a pretty low confidence forecast for
stratus coverage, with the best forecast suggesting more mid-level
cloud cover across the region.

&&

.LONG TERM...
(Monday night through next Saturday)
Issued at 112 PM PDT Sun Sep 15 2024

Temperatures cooler than seasonal averages continue through the next
few days, and another upper level low arrives late Tuesday into
Wednesday. This low isn`t as strong as the one that`s coming through
today, so the winds won`t be as gusty, and rainfall totals will be
similar to those from the system today and Monday. Of note, the
National Blend is trying to slip a very low chance (10-15%
probability) for thunderstorms for the Wednesday system, and a
cursory look at the K-Index suggests that, with values up to 32
across the region, the potential for isolated thunderstorms
exists. Not very confident at this stage for anything to happen,
but definitely something to keep an eye on for the next couple of
days as the forecast is refined.

After the upper level low moves out, the pattern shifts to a slight
ridge with temperatures close to or slightly above seasonal averages
by the weekend, and the CPC outlooks suggest that the seasonal to
warm temperatures continue into the last weekend of September.

&&

.AVIATION...
(06Z TAFS)
Issued at 1016 PM PDT Sun Sep 15 2024

Winds continue to be strong and gusty at this hour for many
terminals, with winds out of the W/NW. These stronger winds will be
slow to diminish through the night, generally not subsiding below 10
knots until closer to sunrise Monday. CIGs will be predominantly
MVFR through the night as low clouds push in, alongside rain shower
chances. Rain chances begin closer to the 12Z time frame Monday,
with rain generally expected to be light. Rainfall chances will
begin to cease in the late morning of Monday. MVFR CIGs will begin
to clear to become VFR in the late morning to early afternoon of
Monday for most terminals with the exception of Monterey Bay.

Vicinity of SFO...Winds continue to gust at this hour to 30 kts and
above, however, these strong westerly winds are expected to slowly
decrease throughout the night beyond the frontal passage. Rain
chances arrive in the early hours of Monday morning, but any rain
that falls is expected to be light. MVFR CIGs will persist through
at least the late morning Monday, with CIGs later lifting to become
VFR, though SCT clouds may still be present.

SFO Bridge Approach...Low clouds are likely to filter into the SF
Bay overnight bringing MVFR CIGs.

Monterey Bay Terminals...MVFR CIGs persist through the TAF period.
Light rain begins towards 12-14Z Monday, but begins to taper off in
the late morning. Westerly winds around 10 knots return in the
afternoon and evening tomorrow.

&&

.MARINE...
(Tonight through next Saturday)
Issued at 1016 PM PDT Sun Sep 15 2024

Buoys continue to report strong NW winds and moderate seas in the
wake a a recent cold front. Seas will continue to build through
Monday, becoming rough in the NW waters as winds very gradually
decrease on Monday. There is a bit of a break on Tuesday before a
second cold front brings the return of strong NW winds and rough
seas to the exposed coastal waters. Overall it will be a
challenging week for smaller craft.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Monday for Mry Bay-Pt Pinos
     to Pt Piedras Blancas 0-10 nm-SF Bay N of Bay Bridge.

     Gale Warning until 3 AM PDT Monday for Pt Arena to Pt Reyes 0-10
     nm.

     Small Craft Advisory until 9 AM PDT Monday for Pigeon Pt to Pt
     Pinos 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

     Gale Warning until 3 PM PDT Monday for Pt Arena to Pt Reyes 10-
     60 NM.

     Small Craft Advisory until 9 PM PDT Monday for Pigeon Pt to Pt
     Pinos 10-60 NM.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...AC
MARINE...Flynn

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