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122
FXUS66 KLOX 211631
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
931 AM PDT Sat Sep 21 2024

.SYNOPSIS...
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21/923 AM.

A warmer and drier pattern will establish through Monday as high
pressure aloft will build over the region. A warmer air mass will
likely remain in place through much of next week away from the
coast with the hottest daytime temperatures forecast for Monday.
Onshore flow will remain in place through the period and keep
night through morning low clouds and fog in the forecast.
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&&

.SHORT TERM (TDY-MON)...
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21/930 AM.

***UPDATE***

No changes to the forecast expected today as the upper low has
departed and warmer weather is expected the next several days.
Ensemble based guidance has been bouncing around a bit with how
much warming due to a weak upper low developing along the CA coast
Sunday into Monday so there remains some uncertainty with that but
either way a warming trend is expected with decreasing marine
layer stratus at least for inland areas. Overall very minimal
weather impacts the next several days.

***From Previous Discussion***

High pressure aloft will slowly build through Monday. A warmer
and drier air mass will settle into the region as 500 mb heights
climb and 1000-500 mb thickness values increase through Monday.
More significant warming is forecast away from the coast between
Sunday and Monday, but most interior coastal and valley locations
will only warm to between 4 to 8 degrees above normal for this
time of year on Monday. A few locations across the interior
portions could warm closer to 7 to 12 degrees above seasonal
normals. Closer to the coast and at the beaches, a persistent
onshore flow and night through morning low clouds and fog will
keep the warming trend moderated. Most coastal cities and locales
will only warm a few degrees of normal. No heat headlines are
anticipated at this time, but there is a 10 percent chance that a
short heat advisory could be issued for the Monday time period
across the interior portions of the area.

.LONG TERM (TUE-FRI)...21/423 AM.

Some cooling is expected to establish for the middle portion of
next week as an upper-level trough currently located near 42N and
138W, or about 1000 miles west-northwest of Point Conception will
dig south along the California coast through Tuesday. The latest
model solutions agree with EPS, GEFS, and CMC solutions that the
trough will pull west of the state for Monday, thereby pumping up
500 mb heights some. By Tuesday, heights fall and thickness
values decline in a majority of the solutions, but CMC and some
GEFS ensemble members hold on the warmer temperatures across the
interior for Tuesday. Onshore flow should strengthen for Tuesday
through Thursday and bring a cooler pattern for the period, but
there is still a large spread across the forecast ensembles at
this time. All of the ensemble temperature means trend cooler,
but there are still a few solutions offering up a warming trend
into Wednesday. Night through morning low clouds and fog should be
more expansive for the period, making a better push into the
valley areas for Wednesday morning, and again Wednesday night into
Thursday morning. For now, NBM temperatures remain in the
forecast Wednesday and Thursday, but much warmer temperatures were
indicated for Tuesday away from the coast than NBM values.

There is a much wider spread of values for Friday and Saturday
across the ensemble members. While ensemble temperature mean
trend warmer into next weekend, some of the deterministic
solutions indicate a hot weather pattern could be setting up. The
forecast goes with NBM values for now, which leans more into a
warming trend.
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&&

.AVIATION...21/1318Z.

At 1259Z at KLAX, the marine layer was 3200 ft deep. The top of
the inversion was at 3900 feet with a temp of 18 C.

High confidence in TAFs for KPMD and KWJF.

Moderate confidence in remaining TAFs due to the uncertainty of
flight cat changes. Flight cat changes could be off by +/- 3
hours.

There is a 20% chance KPRB of LIFR-IFR cigs after 04Z.

For KSBP and KSMX, cigs could return as early as 03Z Sun, with a
25% chance of VLIFR conds after 03Z.

For coastal sites south of Point Conception, there is a 20%
chance of no VFR transition for KSBA and KOXR through the period.
Cigs may scatter out as early as 16Z or as late as 20Z for KLGB,
KLAX, and KSMO. There is a 20% chance that cigs return as early
as 03Z for the coastal sites.

There is a 30% chance of IFR-MVFR cigs at KVNY. There is a 30%
chance of KBUR remaining VFR Sun, if cigs do form, there is a 20%
of IFR cigs.

KLAX...Moderate confidence in TAF. Cigs may scatter as early as
16Z or as late as 20Z. Return of cigs could occur as early as 03Z
Sun. No significant east wind component expected.

KBUR...Moderate confidence in TAF. There is a 30% chance of
remaining VFR Sun. If cigs do form on Sun, there is a 20% chance
of BKN008 cigs.

&&

.MARINE...
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21/834 AM.

For the Outer Waters (Central coast south to San Nicolas
Islands), moderate to high confidence in winds and seas remaining
below Small Craft Advisory (SCA) level thru Wednesday. There is a
20-30% chance for brief SCA level wind gusts near Pt Conception
Sunday evening, and then a 30-50% chance of SCA level wind gusts
beginning late Wednesday afternoon and evening. Looking out ahead
to Thursday and Friday, moderate confidence in widespread SCA
level winds with building steep seas.

For the inner waters along the Central coast, high confidence in
conds remaining below advisory levels through early Thursday, with
moderate confidence in increasing winds in the afternoon.

For the Inner waters south of Point Conception, moderate to high
confidence in conditions remaining below SCA levels through
Wednesday. There is a 20-30% chance of local low end SCA gusts in
the far western portion of the Santa Barbara Channel and the San
Pedro Channel Sunday afternoon. Additionally, there is a 30-40%
chance of SCA level winds across the western portions Wednesday
afternoon.
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&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...MW/Hall
AVIATION...Lund
MARINE...Lewis/Lund
SYNOPSIS...Hall

weather.gov/losangeles

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