909
FXUS66 KMTR 152012
AFDMTR

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

...New SYNOPSIS, SHORT TERM, LONG TERM...

.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.

&&

.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...
(18Z TAFS)
Issued at 1117 AM PDT Sun Sep 15 2024

An early season cold front ahead of an anomalously low upper-level
low will bring a tale of two hazards, wind and precipitation. The
cold front will continue to support gusty winds at all terminals
through the early morning hours of Monday. It isn`t until the
anomalously low upper-level low drops down from the Pacific
Northwest tomorrow morning that the best precipitation chances
emerge. The TAFs were constructed with a four hour timeframe where
probabilities of -SHRA were highest, -DZ is possible preceding
and succeeding that timeframe. Ceilings will be transient between
MVFR and VFR through the TAF period.

Vicinity of SFO...Currently MVFR with gusty westerly flow. Westerly
winds will strengthen with gusts up to 40 knots expected this
afternoon through the early morning hours of Monday. MVFR ceilings
will impact the terminal through most of the TAF period as it is
still not scattered out and ceilings are expected to make an early
return tonight with another late clearing slated for tomorrow. Best
timeframe for precipitation (-SHRA) is 09Z-13Z with -DZ possible
on either side of that timeframe.

SFO Bridge Approach...Low clouds will filter in by 03Z and linger
through the TAF period.

Monterey Bay Terminals...Currently MVFR with westerly flow at both
terminals. Both terminals are expected to briefly improve to VFR
this afternoon with a quick return of MVFR ceilings by this evening.
Winds will prevail out of the west through the TAF period, becoming
gusty this afternoon. Best timeframe for precipitation (-SHRA) is
12Z-16Z with -DZ possible on either side of that timeframe.

&&

.MARINE...
(Today through Friday)
Issued at 911 AM PDT Sun Sep 15 2024

Back to back early season cold fronts will move through the
coastal  waters today and Wednesday resulting in widespread strong
northwesterly breezes with near gale force gusts. In addition,
there  is also up to a 10% chance for thunderstorms which could
produce  lightning, locally heavy rainfall, and locally stronger
winds. Seas  will remain rough outside of protected waters through
the forecast  period.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Monday for Mry Bay-SF Bay N
     of Bay Bridge.

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

     Gale Warning until 9 PM PDT this evening for Pt Pinos to Pt
     Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory until 9 AM PDT Monday for Pigeon Pt to Pt
     Pinos 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...Sarment
MARINE...Sarment

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