270
FXUS66 KLOX 250323
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
823 PM PDT Fri May 24 2024

.SYNOPSIS...24/823 PM.

Strong onshore flow and a deep marine layer will make recurring
night through morning low clouds, fog, and patchy drizzle, with
low clouds reaching the foothills. There is a twenty percent
chance of a light rain shower this evening at mountain locations.
Expect better clearing and warmer temperatures starting Sunday.

&&

.SHORT TERM (FRI-MON)...24/819 PM.

The passage of an upper level trough of low pressure combined
with a strong onshore pressure gradient continues to
generate a deep marine layer pattern (especially for LA/Ventura
counties). Latest ACARS data showing the marine layer depth
has exceeded 4000 feet in the LA Basin, resulting in low clouds
and fog banking up against the lower coastal slopes. There is
still a 10-20 percent chance of light showers across the mountains
of LA/Ventura counties this evening. Another cool day, with
warmer valley/desert locations only topping out in the lower 70s.

In evening update, have extended the wind advisories until 3 am
tonight. Wind gusts of 40 to 50 mph have been observed this
afternoon/evening across the Antelope Valley and adjacent
foothills, as well as the southwest portion of Santa Barbara
County. On Saturday, the strong onshore flow pattern will continue
to generate gusty west winds across the Antelope Valley, with
another wind advisory issuance possible.  Looking for another
day of slow clearing near coast. Little change in overall
temperatures on Saturday, except for a few degrees of warming
expected in the Antelope Valley.

*** From previous discussion ***

Expect a switch to a broad NW flow pattern aloft later tonight
and Sat. Models show some reduction in low clouds tonight as cooling
aloft should help wipe out any weak marine inversion. Expect a
rather less solid and rather haphazard cloud field tonight and Sat
morning, and there should be more in the way of sunshine in most
areas Sat afternoon. Due to increased sunshine and small height
rises, expect a couple of degrees of warming in most areas Sat,
though temps should still be below normal. Strong N-S gradients
will likely produce another round of advisory level winds across
the southwestern coast of SBA County and the western Santa Ynez
mtns late Sat afternoon and evening.

The flow aloft will become even more zonal Sat night and Sun, and
heights will rise a bit Sunday. Expect the marine layer to
reorganize, but be less deep, with night thru morning low clouds
and fog confined mainly to coastal and valley areas Sun morning.
Expect mostly sunny skies in most areas Sunday afternoon, with a
few degrees of warming due to height rises, warming at 950 mb and
slight weakening of the onshore gradients. High temps will likely
rise into the 80s in the Antelope Valley, and could even approach
80 degrees in the Salinas and Cuyama Valleys. Temps should rise
into the mid to possibly upper 70s in the warmest valley locations
in L.A. and Ventura Counties.

Monday will be similar to Sunday, with the NBM mean solutions
building the ridge which should allow a little more clearing and
warming. Downtown LA should see the afternoon high at a seasonal
low 70s, while Paso Robles could make it into the low 80s, and
Antelope Valley into the high 80s.

.LONG TERM (TUE-FRI)...24/134 PM.

Models are in fairly good agreement in showing an upper low
moving toward the coast of southwestern Canada Tue, then dropping
slowly southeastward with a trough extending into northern
California. Our area will see the effect of that feature in a
weakening of the ridge on Wednesday and a more zonal pattern on
Thursday and Friday. EFI wasn`t pointing to anything
climatologically abnormal in the long term, but the NAEFS
percentile was showing stronger than normal winds over the waters
along the coast Wednesday. Overall, expect rather benign weather
Tue thru Fri, with areas of night/morning low clouds in coastal
and most valley areas.

&&

.AVIATION...24/2307Z.

At 2230Z at KLAX, the marine layer was 4500 ft deep. The top of
the inversion was at 5600 feet with a temperature of 12 C.

For the 00Z TAF package, high confidence in desert TAFs and low to
moderate confidence in coastal/valley TAFs. Lower confidence in
coastal/valley sites due to uncertainties in the behavior of the
marine layer stratus.

KLAX...Moderate confidence in 00Z TAF. High confidence in return
of MVFR CIGs, but low confidence in timing of return (could be +/-
4 hours of current 05Z forecast). No significant easterly wind
component is expected.

KBUR...Moderate confidence in 00Z TAF. High confidence in return
of MVFR CIGs, but low confidence in timing (could be +/- 3 hours
of current 07Z forecast).

&&

.MARINE...24/803 PM.

Moderate to high confidence in forecast, with higher confidence
in winds relative to seas.

Across the outer waters, Small Craft Advisory (SCA) level winds
are expected to persist through late Saturday night. Sunday and
Monday afternoons/nights there is a 50-70% chance of SCA winds.
Starting Tuesday morning, chances of SCA winds will increase to a
60-80% chance, with a 30-40% chance of Gale Force winds Tuesday
night through Wednesday.

Across the nearshore waters along the Central Coast, there is an
80% chance of SCA conds through much of tonight, and again on
Saturday afternoon and night. There is a 30-40% chance of SCA
winds during the afternoon and evening hours Sunday and Monday.
Tuesday afternoon through Wednesday, SCA level winds are likely
(60-70%, with a 20-30% chance of Gale Force winds.

Across the southern inner waters, there is a 70-80% chance of SCA
level winds across the the Santa Barbara Channel (strongest in the
western portion) tonight, and again Saturday afternoon and
evening. There is a 30% chance that there will be no break in SCA
winds for the western and central portions of the channel Saturday
morning. South of the Channel Islands, there is a 50-70% chance
of SCA level winds pushing into the western portion of the
southern inner waters tonight with choppy SCA seas. There is a
30-40% chance of this reoccurring Saturday evening. Winds and seas
should drop below SCA levels Sunday through Tuesday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory now in effect until 3 AM PDT Saturday for zones
      349-351-381>383. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Saturday for
      zones 645-650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Sunday for
      zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Gomberg/jld
AVIATION...RAT
MARINE...Gomberg/Schoenfeld
SYNOPSIS...Gomberg

weather.gov/losangeles

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