756
FXUS66 KLOX 140459
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
959 PM PDT Tue Aug 13 2024

.SYNOPSIS...13/201 PM.

Temperatures will remain below to near normal though this
weekend, with overnight to morning low clouds and fog across
coastal areas at times. Over the next few days, gusty winds are
likely across the Santa Barbara southwestern coast and the
Antelope Valley during the evenings.

&&

.SHORT TERM (TUE-FRI)...13/958 PM.

***UPDATE***

Temperatures trended cooler today (about 2 to 7 degrees of
cooling for most of the area) with most areas reaching the 80s to
90s. Coasts were stuck in the 60s to 70s, with especially cool
values along the Central Coast due to strong onshore flow and
lingering marine layer clouds. Heights are forecast to rise
overnight tonight and through Wednesday (peaking near 594 DAM),
which should lead to temperatures trending slightly warmer most
regions. This slight warming trend should continue into Thursday
as high pressure continues to build.

Marine layer clouds were limited with very patchy coverage over
the area this morning. Most of the clouds were confined to the
Central Coast, and from the Ventura Coast southward. It is unclear
how much marine layer clouds will redevelop, especially under
rising heights and with plenty of dry air aloft that could mix
downward. So far, clouds have only developed over coastal areas
just north of Point Conception and portions of the immediate LA
County coast. Expecting more clouds to develop and move into the
Central Coast along with the LA Basin, but low confidence in
clouds reaching the Ventura County coast.

Sundowner winds have developed over western portions of the Santa
Ynez Range with gusts of 30 to 40 mph. Winds should remain below
sub-advisory levels tonight. However, Sundowner winds will
reoccur each night, with better chances to reach advisory levels
Wednesay night and Thursday night.

***From Previous Discussion***

The broad high pressure system centered well southwest of SoCal
will begin to build back today and Wednesday. 500 mb heights will
rise from 588-590 dam today to 592-595 dam by Wednesday night.
Friday, a powerful trough with a low pressure center of around 563
dam will start stalling to the west of Oregon and Washington State.
The trough will nudge the previously mentioned high pressure
center to the east, bumping it to around Arizona and New Mexico,
and heights over SoCal will fall again to around 589-591 dam
Friday.

The overall temperature pattern will generally a;light with the
500 mb heights, however fluctuations each day will be fairly
minimal through Friday. Expect the coolest temperature today,
followed by slight warming Wednesday and Thursday, as hieghts rise
and onshore flow decreases. Despite a warming trend, even
Thursday temperatures will be near normal for much of the region,
except for the Santa Barbara South Coast which will see
temperatures several degrees above normal. Friday, as heights fall
and onshore gradients pick up again, temperatures will drop a
couple degrees.

Strong north-to-south pressure gradients tomorrow night and
Thursday night will drive Sundowner winds across the Santa Barbara
South Coast. Across the southwest portion gusts are expected to
be 35 to 50 mph, with the eastern Santa Ynez mountains and
foothills likely to see gusts 25 to 35 mph. Wind Advisories are
likely to be issued for tomorrow evening and Thursday evening for
the Southwestern Santa Ynez range and coastline below.
Downsloping compressional heating will produce warm temperatures
across the whole Santa Barbara South Coast (including Santa
Barbara City), with highs several degrees above than normal.
Elsewhere, onshore pressure gradients will continue to yield the
typical southwesterly to westerly wind gusts during the afternoons
and evenings across the Antelope Valley/foothills through the
Highway 14 Cooridor, with gusts 20 to 40 mph common.

Low clouds and fog will prevail for the beaches during the
overnight-to-morning hours. However due to lackluster onshore
pressure gradients and high pressure, the inland extend of marine
layer clouds is likely to be limited. With one possible exception
for the Los Angeles County coastal plains tomorrow night and
Thursday night. A high north- to- south pressure gradient for the
region signals that a moderate Catalina Eddy may form both
nights, lifting the marine layer and increasing low cloud coverage
for the Los Angeles Basin.

.LONG TERM (SAT-TUE)...13/255 PM.

Starting this weekend, there is high confidence that the region
will remain under a stagnant pattern. The region will be under the
intersection of a trough just west of the Pacific Northwest and
high pressure center over the desert southwest. Ensembles indicate
some uncertainty in the exact 500 mb heights values as well as
the location of the high pressure system. This translates to
uncertainty in the precise temperatures each day and chances of
monsoonal moisture. Overall temperatures appear to be warmest on
Monday and Tuesday. North- to- south pressure gradients indicate
that Sundowner winds will continue during the evenings for the
Santa Barbara southwest coast.

Chances for monsoonal mositure starts to increase starting
Saturday. Based on the ensembles, Saturday through Tuesday there
is about a 20 to 30 percent chance of monsoonal mositure that
would be favorable for thunderstorms. Overall thunderstorm
chances remain under 10 percent in the long term. Looking ahead,
based on Climate Prediction Center`s precipitation outlook, the
area southeast of Los Angeles county is leaning above normal for
days 8 to 14. This indicates that the slight chance of monsoonal
mositure/thunderstorms will continue beyond Tuesday for Los
Angeles (and maybe Ventura) county.

&&

.AVIATION...14/0134Z.

At 2359Z at KLAX, the marine layer was 700 ft deep. The top of
the inversion was at about 2500 ft with a temperature of 25 C.

High confidence in CAVU TAFs for KPRB, KBUR, KVNY, KPMD, and
KWJF.

Moderate to low confidence in coastal TAFs. Timing of cat changes
may be off by +/- 2 hours from current fcst. There is a 20-30%
chance of IFR conditions after cigs arrive. VFR conditions
expected at these sites by 17Z. There is a chance that KSBA
(40%), KOXR (20%), and KCMA (40%) site will remain VFR through
the period.

KLAX...Moderate confidence in TAF. Timing of cat changes may be
off by +/- 2 hours from current fcst. There is a 30% chance of
cigs lower than 005 at any point between 09Z and 13Z. 20% chance
of VFR conditions before 17Z. No significant east wind component
expected.

KBUR...High confidence in CAVU TAF.

&&

.MARINE...13/849 PM.

For the outer waters, moderate to high confidence in current
forecast. Small Craft Advisory (SCA) level winds and seas expected
through at least Sunday night. There is a 30-50% chance of low
end gale force wind gusts in the afternoon thru late night hours
Wednesday thru Friday (with the highest chances on Thursday), and
a 10% chance Saturday and Sunday.

For the inner waters north of Point Sal, moderate confidence in
current forecast. SCA level winds and seas are likely (60-70%
chance) much of the time Wednesday afternoon through Thursday
night. There is a 50-60% chance of SCA level winds and seas in the
afternoon thru evening hours on Friday, and a 30-40% chance
Saturday and Sunday Sunday.

For the inner waters south of Point Conception, moderate
confidence in current forecast. There is a 30-50% chance of SCA
level wind gusts for the western Santa Barbara Channel during the
afternoon into late evening hours through Thursday, and a 20-30%
chance of SCA level winds Saturday and Sunday in the afternoon to
evening hours. Otherwise, conds will remain below SCA levels over
the southern inner waters through Sunday night.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 3 PM Wednesday to 5 AM
      PDT Friday for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 2 PM PDT Thursday for
      zones 670-673-676. (See LAXMWWLOX).
     Gale Watch in effect from Thursday afternoon through late
      Thursday night for zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Phillips/Schoenfeld
AVIATION...Phillips
MARINE...Lewis/Schoenfeld
SYNOPSIS...KL/Schoenfeld

weather.gov/losangeles

Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox