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000
FXUS66 KLOX 291559
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
859 AM PDT Mon May 29 2023

.SYNOPSIS...29/857 AM.

A strong onshore flow pattern will keep a persistent and deep
marine layer in place for most of this week. Night through
morning low clouds and fog with limited afternoon clearing will
continue as well. Areas of drizzle or light rain can be expected
during the night and morning hours through Tuesday. There is a
slight chance of thunderstorms in the mountains Tuesday afternoon
and evening. Temperatures will be below normal for most of the
week. Some warming is possible late in the week into the weekend.

&&

.SHORT TERM (TDY-WED)...29/858 AM.

***UPDATE***

Another day with a deep marine layer and clouds well up the
coastal slopes and knocking on the door of the Antelope Valley.
Pilot reports in the LA Basin peg the marine layer right around
4500 feet while it`s only slightly shallower north of Pt
Conception based on the VBG sounding. An upper low just west of
SFO this morning has ushered in cooler air aloft, weakening the
marine inversion by at least 3 degrees C. The visible satellite
image shows quite a bit more thinning of stratus over the coastal
waters and even partially over the land so there`s a slight chance
that we could see a reverse clearing pattern today where clouds
clear more near and over the ocean but very little if any
clearing inland. In any case, temperatures expected to again be
5-10 degrees below normal, with the biggest changes today being in
the mountains and interior areas where highs will be 4-8 degrees
cooler than Sunday. Elsewhere, very similar temps are expected.

***From Previous Discussion***

An upper low just to the west of San Francisco early this morning
will drop southward today and tonight, reaching a position about
150 nm west of Point Conception late tonight. It will then move
eastward right across the forecast area on Tue. Expect the deep
marine layer to persist, with clouds in all coastal and valley
areas tonight, once again reaching the coastal slopes. Once again
there will be areas of drizzle or light measurable rain,
especially in the foothills. Do not expect too much clearing west
of the mountains Tue as onshore gradients will remain strong, but
with the upper low overhead, confidence is a bit lower in the
cloud forecast for Tue afternoon. Models continue to show some
insatiability in the mtns of SBA, VTU and L.A. Counties Tue
afternoon and evening, and there will be more in the way of mid
level moisture. Have added a slight chance of afternoon and
evening showers and thunderstorms for these areas. This may have
to be expanded into the Antelope Valley and the interior valleys
of SLO and SBA Counties, but confidence is lower there. Expect
little change in max temps on Tue.

The upper low will move to the east of the region Tue night and
Wed. The marine layer will remain quite deep, but heights will
rebound a bit Wed, possibly allowing the marine layer to become a
bit more shallow. However, onshore gradients will remain very
strong, so it is difficult to expect too much improvement on Wed--
perhaps partial clearing in some areas west of the mountains and
a slight bump in temps.

.LONG TERM (THU-SUN)...29/449 AM.

Another upper low will develop to the southwest of the region Wed
night and Thu, then pass south of the area Thu night. Latest
operational runs of both the GFS and the EC are more progressive
with this feature, with some weak ridging developing across the
area Fri and persisting into the weekend. If this comes to be,
there will be another night of deep marine layer with widespread
night through morning low clouds in coastal and valley areas Wed
night, with continued slow clearing and cool conditions on Thu.
Then, there may be a decrease in night/morning low clouds Fri thru
Sat or possibly even Sunday, with better clearing, and some
warming both Fri and Sat. However, with the way things are going
this spring, it is very possible that the trough will end up
persisting.

&&

.AVIATION...29/1232Z.

At 0621 at KLAX, the marine layer 3300 ft deep. The top of the
inversion was 4000 feet with a max temperature of 14 degrees C.

For coastal and valley sites, moderate confidence in latest TAFs
with a 20-40% chance of one category lower CIGs. There is a 30-40%%
chance that CIGs will scatter out after 20Z. High confidence in
desert TAFs.

KLAX...Moderate confidence in TAF. There is a 30-40% chance that
CIGs will scatter out after 20Z. No significant easterly wind
component is expected.

KBUR...Moderate confidence in TAF. There is 30-40% chance that
CIGs will scatter out after 20Z.

&&

.MARINE...29/856 AM.

For all waters, high confidence in current forecast through
Wednesday. For this period winds and seas are expected to remain
below Small Craft Advisory (SCA) levels.

Moderate confidence that Wednesday afternoon widespread SCA level
winds, and borderline SCA level seas will spread over the outer
waters and the western portion of the Santa Barbara Channel.

&&

.BEACHES...29/857 AM.

Long-period south swell originating from the Southern Hemisphere
will continue across the coastal waters through Tuesday. Strong
rip currents and elevated surf of local 3 to 5 feet will be
possible through Tuesday. There will be the potential for
hazardous rip currents and a Beach Hazards Statement may be
needed.

&&

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

&&

$$

PUBLIC...MW/DB
AVIATION...Schoenfeld
MARINE...Sweet/Schoenfeld
BEACHES...Sweet
SYNOPSIS...DB

weather.gov/losangeles

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