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000
FXUS66 KMTR 132004
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
104 PM PDT Sat Apr 13 2024

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

.SYNOPSIS...
Issued at 102 PM PDT Sat Apr 13 2024

Rain showers and isolated thunderstorms will continue this afternoon
and into the overnight hours while shifting southward. Storm chances
decrease overnight, but showers linger into Sunday afternoon before
dry weather returns. A warming trend is then expected throughout
the upcoming week.

&&

.SHORT TERM...
(This evening through Sunday)
Issued at 102 PM PDT Sat Apr 13 2024

By this afternoon and evening we will transition to post frontal
rain showers and isolated thunderstorms as the atmosphere aloft
becomes more unstable. CAPE values are forecast to be between 200-
300 J/kg with little to no CIN. Any heavier showers and/or
thunderstorms will be capable of producing brief heavy rainfall,
gusty winds, copious amounts of small hail, occasional lightning,
and rapid onset of flooding. Thunderstorm potential will shift
southward tonight and diminish Sunday morning.

Lingering showers will be possible over the Central Coast through
Sunday afternoon with conditions clearing out by the late evening.
Temperatures will struggle to warm into the upper 50s near the coast
to low/mid 60s inland on Sunday (40s in the highest peaks).

&&

.LONG TERM...
(Sunday night through next Friday)
Issued at 102 PM PDT Sat Apr 13 2024

High pressure will begin to build in wake of the exiting weather
system and will allow for a warming and drying trend to resume. By
Wednesday and Thursday, expecting the interior to warm into the
upper 70s to lower 80s with upper 60s to mid 70s near the coast.
Friday and beyond, zonal flow sets up across the region allowing for
a few degrees of cooling across the interior and more so at the
coast with a likely return of a marine layer.

&&

.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 102 PM PDT Sat Apr 13 2024

Breezy fresh to strong winds continue across the coastal waters
ahead of an approaching 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 afternoon
before transitioning to a more scattered, convective precipitation
mode by the evening. 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 until 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 Pinos
     to Pt Piedras Blancas 0-10 nm.

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

&&

$$

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

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