-- Discussion containing changed information from previous version are highlighted. --
944
FXUS66 KLOX 240435
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
935 PM PDT Thu May 23 2024

.SYNOPSIS...23/901 AM.

Strong onshore flow and a deep marine layer will keep the night
through morning low clouds and fog pattern going with low clouds
reaching the foothills each day. There will be patchy drizzle each
morning. The near shore area will see limited or no clearing through
Saturday. High pressure will bring better clearing and warmer
temperatures to the area starting Sunday and continuing into next
week.

&&

.SHORT TERM (THU-SUN)...23/840 PM.

***UPDATE***

The marine layer is about 3700 ft deep and the capping inversion
is fairly week. NW flow across the outer waters has eliminated the
clouds there. The NW flow across SBA county has eliminated most of
the clouds across the SBA south coast. An odd little impulse
moving from Orange County into LA county cleared the low clouds
from the southern portion of LA county.

The strong onshore flow kept the low clouds in the vlys today and
this brought about 4 to 8 degrees of cooling. The clouds were thin
enough across the coasts to allow for a few degrees of warming. It
was a rather cool day with max temps 4 to 8 degrees blo normal.

It was a windy day across the Antelope Vly. The 10 mb onshore push
this afternoon created low end advisory level gusts of 45 to 50
mph across the western vly floor and foothills.

Overnight the low clouds should stay put over The LA/VTA county
csts/vlys/foothills and mtn passes. SBA and SLO counties should be
mostly clear save for the Central Coast and perhaps (30 percent
chc) the Santa Ynez Vly.

Tomorrow`s forecast is a tricky one. A decent (for late May) trof
will move over the area during the day. In the morning its lift
should be enough to produce some local drizzle esp near the
foothills. In the afternoon the trof axis moves over the LA mtns
which will be somewhat unstable due to the sunshine. The very deep
marine layer could provide just enough moisture for a shower. The
chc of showers from all of this is 20 percent.

The inversion is also so weak that there is a 40 percent chc that
the trof will mix the marine layer out and skies will be sunny.
Took a somewhat wishy washy approach and took the middle ground
with the stratus layer turning into a partly to mostly cloudy
strata cu deck.

The cool air advection with the trof will bring serious cooling of
5 to 10 degrees to the interior but the weaker marine layer will
allow the coasts to warm a few degrees.

The cold air advection and strong pressure gradients will bring
advisory level wind gusts to most of the Antelope Vly and its
foothills as well as the SW corner of SBA county.

Will up date the forecast to adjust the clouds, Friday`s max temps
and add wind advisories.

***From Previous Discussion***

Cst/Vly temps will not change much but the cool air behind the
trof will cool the interior by 4 to 8 locally 10 degrees. Max
temps will only be in the 60s across the csts/vlys and in the 70s
for the interior. These max temps are mostly 10 to 15 degrees blo
normal.

Saturday should bring a continuation of the low cloudiness. There
is a chance (40 percent) that the marine inversion will be mixed
out and skies will be much clearer/sunnier than currently fcst. If
there are morning low clouds, offshore trends should make for
faster clearing although some beaches may remain cloudy. Max temps
will warm some but hgts will not have recovered enough to bring
anything more than a couple of degrees.

On Sunday the broad west coast trof will finally push to the east
and will be replaced by a weakly building ridge. Hgts will rise
from 577 dam to ~580 dam on on Sunday. The onshore flow will
weaken and the N to S gradient may even turn briefly offshore.
The night through morning low cloud pattern will continue but the
higher hgts will push the marine layer down a bit and this along
with the weaker onshore push will limit the vly penetration. N to
S offshore flow across the SBA south coast may keep that area
clear. The low clouds should clear earlier and more completely
than they did today. The residual cool air will no longer exist
in the interior and that will allow a 5 to 10 degree warm up
across the interior on Sunday while the csts/vlys will warm 2 to 4
degrees.

.LONG TERM (MON-THU)...23/119 PM.

Models continue to remain in good agreement through Tuesday.
European solutions keep a though down through central CA on Wed
and Thu while GEFS is less so, but in SoCal there is fairly good
agreement.

As hgts continue to rise under the building ridge through Tuesday
look for about 2 to 4 degrees of warming each day. Max temps on
Tuesday will finally come within a few degrees either side of
normals. Look for an increase in marine layer coverage and a slow
down in clearing as well as downward trend in temperatures on Wed
and Thu as the ridge flattens and an onshore flow pattern remains.

&&

.AVIATION...24/0023Z.

At 23Z at KLAX, the marine layer was 3600 ft deep. The top of the
inversion was at 5600 feet with a temperature of 16 C.

High confidence in desert TAFs.

Low to moderate confidence in remainder of TAFs. There is a 30
percent chc that the low clouds could dissipate some time this
late evening or after midnight. There is also a 30 percent chc
that cigs will remain AOA OVC020 at any site.

KLAX...Low to moderate confidence in TAF. There is a 30 percent
of SCT conds developing and persisting into the early morning
hours. Flight Cat changes could be off by +/- 2 hours. High
confidence in any east wind component remaining less than 6 kt.

KBUR...Moderate confidence in TAF. There is a 30 percent
of SCT conds developing later this evening. Flight Cat changes
could be off by +/- 2 hours.

&&

.MARINE...
-- Changed Discussion --
23/933 PM.

Moderate to high confidence in the current forecast. Higher
confidence in wind forecast relative to sea forecast.

Across the outer waters, there is a 80-100 percent chance of
Small Craft Advisory (SCA) level winds through at least late
Friday night, decreasing to 60-80 percent between Saturday and
Sunday. Widespread SCA conditions (winds and seas) are likely
especially between Friday afternoon and Friday night. There is a
moderate chance that winds could drop below SCA levels on
Saturday morning. Winds may drop below SCA levels late Sat
night/Sun morning. There is a 40 percent chance of SCA level
winds on Monday increasing to 60 percent on Tuesday.

Across the nearshore waters along the Central Coast, there is a
30 percent chance of SCA level winds tonight, increasing to 80
percent on Friday afternoon and night, and again on Saturday
afternoon and night. There is a high chance of widespread SCA
conditions (winds and seas) on Friday afternoon and evening. There
is a 30 percent chance of SCA winds during the afternoon and
evening hours Sunday and Monday.

Across the Santa Barbara Channel and into the southern inner
waters, there is a 70-80 percent chance of SCA level winds across
the western and central portions of the Santa Barbara Channel
Friday afternoon and evening, and again Saturday afternoon and
evening. Farther to the south, there is a 30-50 percent chance of
SCA level winds pushing into the southern inner waters Friday
evening and again Saturday evening. Winds and seas should drop
below SCA levels between Sunday and Tuesday.
-- End Changed Discussion --

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CA...Wind Advisory in effect from 2 PM to 9 PM PDT Friday for
      zones 349-351-381>383. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 9 AM Friday to 3 AM PDT
      Saturday for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM Friday to 3 AM PDT
      Saturday for zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Sunday for
      zones 670-673-676. (See LAXMWWLOX).
-- End Changed Discussion --

&&

$$

PUBLIC...Rorke/jld
AVIATION...Rorke
MARINE...Hall
SYNOPSIS...30

weather.gov/losangeles

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