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000
FXUS66 KMTR 131816
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1116 AM PDT Sat Apr 13 2024

...New AVIATION...

.SYNOPSIS...
Issued at 339 AM PDT Sat Apr 13 2024

The rain band builds inland this morning, offering widespread rain
and breezy to gusty winds. Showers and storm chances last through
the day and into the night. Storm chances decrease overnight, but
showers linger into Sunday afternoon before dry weather returns.

&&

.UPDATE...
Issued at 848 AM PDT Sat Apr 13 2024

Low pressure that has been slowly creeping down the coast this
morning, bringing rainfall to our entire service area, is showing
signs of slight southeastward movement. This is giving just enough
push to kick the main frontal boundary through the Bay Area and
Central Coastal midday. While the steady rain will taper, we will
enter into showers and possible thunderstorms for the afternoon
and evening. This is a cooler air mass aloft, which means the
threat for convection is present. With Sea Surface Temperatures
(SST) in the 52-55 degree range, this could provide enough
instability over the coastal water to get convection going and
translate inland. We`ll be watching this closely through the day
and evening hours. Thunderstorms could bring localized gusty
winds, copious amounts of small hail, and rapid onset flooding. In
short, it will be an active afternoon. Stay ready.

&&

.SHORT TERM...
(Today and tonight)
Issued at 339 AM PDT Sat Apr 13 2024

The main rain band is moving inland along the cold front, bringing
moderate rainfall. The rain band will become less organized as it
continues to move inland, leading to more widespread rain but with
reduced rain rates. Shower activity lasts behind the front, with
weaker, but still breezy winds expected through the day. The cold
front`s parent low moves onshore and inland in the afternoon and
into the night, providing additional scattered showers and storm
chances.

Storm chances will peak around 30% into this evening and into the
early night, with the focus being off the coast of Santa Cruz Co and
the Monterey Bay.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 339 AM PDT Sat Apr 13 2024

Thunderstorm chances dissipate into early Sunday morning with
showers lingering into the afternoon before exiting.

Afterwards, a ridge pattern builds in quickly, allowing for dry
weather to return into next week. This will also put the region into
another warming trend with highs ranging from the 60s (along the
coast) to the 80s (in more interior areas) expected in the middle of
the work week and into the next weekend.

The longer term forecast models keep the ridge pattern in place
beyond next weekend, but the ridge shifts slightly east, allowing
for more onshore flow. This will cool temperatures, but still
prevent rain from returning to the forecast.

&&

.AVIATION...
(18Z TAFS)
Issued at 1116 AM PDT Sat Apr 13 2024

VFR is prevailing at all terminals as of 11 am. Some lower deck
are lingering around but only in the FEW or SCT categories. We are
behind the front now and the rain is turning to passing showers.
Some of these showers may be heavy at times and produce small
hail. Models are not handling the winds well at all, showing winds
generally out of the SW while observations have winds out of the
E-SE. As such, this forecast deviates quite a bit from model
guidance and leans on the what observations are showing. Generally
winds will be a bit lighter than forecast earlier this morning due
to the easterly nature. When out of the east, terrain breaks up
the winds a bit more and does not allow them to get moving rapidly
like they would over the water. The caveat to this is in valleys
and drainages. OAK showed a peak gust to 35 knots around 11 am,
but quickly dropped back towards 28 knots. This was likely an
artifact of wind direction creating an acceleration down a
drainage. All that to say, winds will be the tricky part today.
Gusty winds are likely due to showers and thunderstorms crossing
the area this afternoon, but the standard ambient wind should
behave. Showers and thunderstorms will remain in the forecast
through early Sunday morning as the area of low pressure slides to
the SE and exits the region overnight into Sunday. Expect several
updates to the TAFs as the day goes on.


Vicinity of SFO...VFR is expected through the next 36 hours with
occasional bouts of MVFR or IFR if/when strong showers or
thunderstorms cross the area. Winds will be the biggest issue
today as they are expected to remain out of the SE until tomorrow
morning. There may be some wiggle in there from SE to SSW and back
again, but South winds are in the forecast. They will also be
gusty at times as a result of the broader scale low pressure
system and in and around showers and thunderstorms.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR with periods of MVFR or IFR in and
around showers and thunderstorms. Monterey County is just getting
on the backside of the main front, but showers and thunderstorms
are trailing behind. Winds have been more easterly and
southeasterly this morning than models would have indicated and it
is now expected they remain as such through the evening hours.

&&

.MARINE...
(Today through Thursday)
Issued at 339 AM PDT Sat Apr 13 2024

Breezy fresh to strong winds continue across the coastal waters
ahead of an incoming low pressure system and it`s cold front. The
occasional near gale force gust, particularly in the southern
coastal waters, cannot be ruled out. With this system, widespread
light to moderate rain will continue through Saturday morning
before  transitioning to a more scattered, convective
precipitation mode  by the afternoon. Thunderstorm potential
increases to 25 to 30%  Saturday afternoon and evening with
chances decreasing overnight  into Sunday morning. Moderate period
northwesterly swell will  continue to build through the waters
through Saturday before  beginning its abating trend Sunday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Sunday
     for SF Bay N of Bay Bridge.

     Small Craft Advisory until 3 AM PDT Sunday for Mry Bay-Pigeon Pt
     to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena
     to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory until 9 PM PDT this evening for Pt Arena to
     Pt Reyes 10-60 NM-Pt Reyes to Pigeon Pt 0-10 nm.

&&

$$

SHORT TERM...BFG
LONG TERM....Murdock
AVIATION...BFG
MARINE...RGass

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