337
FXUS66 KMTR 151620
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
920 AM PDT Sun Sep 15 2024

...New UPDATE, MARINE...

.SYNOPSIS...
Issued at 203 AM PDT Sun Sep 15 2024

Gusty winds and cooler temperatures today as a potent upper low
digs into the west coast. Below normal temperatures last through
mid week with a second upper low moving in. Gradual warmup into
next weekend.

&&

.UPDATE...
Issued at 911 AM PDT Sun Sep 15 2024

Widespread stratus continues across the inland valleys, with the
colder temperatures and deeper marine layers slowing the
dissipation of the stratus, perhaps sometime in the afternoon if
at all. The cold front is making its way through the SF Bay Area,
with gusty winds already observed and continuing to build through
the day. A few hundredths of an inch of drizzle have already
fallen in terrain-favored locations in the Bay Area. More rain is
expected through Monday morning. For more information, see the
previous discussion.

DialH

&&

.SHORT TERM...
(Today and Monday)
Issued at 203 AM PDT Sun Sep 15 2024

Hints of the approaching system beginning to show up this morning
in the form of gusty winds and very light, isolated showers. As of
writing, the initial cold front is located over Mendocino county,
and will continue to move southward through the Bay Area by about
midday today. There is some evidence of light showers with rain
making it to the ground as some Alert CA cams in Mendocino county
show a few drops on the lenses. Current thinking for rainfall
across the Bay Area hasn`t changed much. Still on the order of a
few hundredths to a tenth or so for those that are lucky enough to
see rain (generally coastal and terrain enhanced areas). Winds
will continue to increase through the day today, and should peak
by late tonight/early Monday morning as the trough axis swings
inland. Most areas will likely see gusty winds to an extent
through this afternoon and evening, but the strongest winds will
be in the favored NW flow coastal areas (e.g. Sonoma coast, Golden
Gate, and Santa Cruz Co coast west of Capitola) and NW/SE
oriented valleys and gaps (e.g. Salinas Valley, East Bay Valleys,
and the San Bruno Gap near SFO). Will other locations generally
see 25-30 mph winds, these favored areas have to potential to see
35-40 mph, with occasional gusts of 45-50 mph. We are holding off
on a Wind Advisory on this shift since we will only touch the
lower criteria in a few isolated areas for a relatively short
period of time. Winds begin to diminish early Monday morning, and
will give way to what should be a very pleasant, cool day across
much of the region with highs ranging from the upper 50s to
mid-70s.

&&

.LONG TERM...
(Tuesday through Saturday)
Issued at 203 AM PDT Sun Sep 15 2024

By midweek, we could be looking at a deja vu situation, but with
slightly less wind. Another cold-core system is poised to slide
down the west coast and basically follow in the footsteps of the
system that is moving in today (as far as we`re concerned for our
region). A bit less dynamic in the upper levels, we wouldn`t
expect as much wind from the midweek system, but we do have
another shot for some light rainfall Wednesday. Still nothing
astonishing as far as rainfall totals go. Perhaps a few hundredths
here and there. Nevertheless, great for putting a slight damper on
our local fire season. After the Wednesday system departs, the
pattern begins a swing back towards slight ridging with
temperatures increasing to around normal by the weekend.

&&

.AVIATION...
(12Z TAFS)
Issued at 359 AM PDT Sun Sep 15 2024

Stratus has filled into most terminals this morning, bringing a
spread of IFR and MVFR CIGs. However, as a low pressure system
approaches, expecting most CIGs to raise to become MVFR given the
ample lifting factor. SF Bay and Monterey Bay terminals are likely
to see MVFR CIGs persist throughout the TAF period given ample
onshore flow and strengthened winds as the gradient tightens. Winds
will be predominantly W/NW and moderate and gusty for most terminals
today. These stronger winds will persist through the late night, and
will be slow to diminish into Monday morning. Light rain chances
begin to arrive towards the end of the TAF period for select
terminals.

Vicinity of SFO...Currently IFR CIGs, but expected to become MVFR
CIGs within the next hour or two. Winds are beginning to strengthen
out of the west and will continue to do so throughout the day today,
becoming strong and gusty in the afternoon with gusts reaching 35+
kts. Stratus and MVFR CIGs are thought to last through much of the
day given the strengthened onshore flow. Moderate confidence on MVFR
CIGs lasting through the day. It is not until the extended portion
of the TAF that winds begin to decrease below 10 knots.

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

Monterey Bay Terminals...IFR CIGs will continue to lift through the
morning to eventually become MVFR. MVFR conditions are expected to
last throughout the remainder of the TAF period with moderate-high
confidence. Moderate confidence is only because there is some chance
that CIGs could lower early Monday morning to become borderline IFR.
However, highest confidence is currently in CIGs maintaining MVFR
status late this morning and beyond. Winds will strengthen through
the late morning to become NW and gusty, lasting through the late
night. Rain chances approach early Monday morning.

&&

.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...Behringer
LONG TERM....Behringer
AVIATION...AC
MARINE...Sarment

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