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000
FXUS66 KLOX 202119
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
219 PM PDT Sat Apr 20 2024

.SYNOPSIS...20/145 PM.

Low clouds and fog will be present on the coastal side of the
mountains through at least the middle of next week, least
expansive on Sunday. Sunday will be the warmest with temperatures
5 to 15 degrees above normal, with steady cooling to follow.
Drizzle is expected Tuesday through Thursday with a chance for
light rain around Friday.

&&

.SHORT TERM (TDY-TUE)...20/222 PM.

Low clouds are slow to burn off from Santa Barbara to Oxnard this
afternoon, and look poised to be around for most if not the rest
of the afternoon, and push into Los Angeles County quickly by
Sundown. The expected clearing trend over the Central Coast
materialized, but the wisps of clouds left in its wake bring
little confidence on what will happen overnight. Could see it stay
clear with the added bonus of light offshore flow forming
overnight, but could also see low clouds forming as it cools down
this evening.

A ridge of high pressure will quickly form overhead on Sunday,
while onshore pressure gradients weaken. This should result in
less marine layer coverage and noticeable warming away from the
coast. Highs in the 80s will be common, with a 90 or two in the
range of outcomes. The Central Coast could also see warming well
into the 70s and maybe lower 80s if they stay clear. All coastal
areas however will be at the mercy of the often unpredictable ebbs
and flows of the marine layer.

As quickly as the ridge forms, it will be replaced by lower
pressure aloft Monday and Tuesday with strengthening onshore flow.
As a result, the marine layer should expand and deepen each day.
Drizzle is possible, especially on Tuesday when most projections
show low clouds pushing deep into the coastal slopes. Temperatures
will lower everywhere as a result.

Northwest to northeast wind gusts of 20 to 30 mph will form over
the mountains and deserts this evening, then turn onshore by
Monday and Tuesday.

.LONG TERM (WED-SAT)...20/222 PM.

Most computer projections (EPS, GEFS, CMC) show a low pressure
system forming over the western United States for the back half of
next week. There is a wide range of outcomes however in terms of
path and timing. The outcome will likely fall between two
potential scenarios of 1) an inside slider (system tracks over
Eastern California) which would bring no rain and some gusty north
winds, and 2) a system riding the coastline which would bring
some light rain and winds delayed into the follow week. There are
enough solutions (20-30%) that show some rain, and considering the
presence of a lot of low-level moisture from the marine layer
leading up, a slight chance of rain seems warranted. The NBM
blend of models continue to project chances of rain under 10%,
but that is likely a consequence of model post-processing
artificially lowering those chances based on the mostly dry last
couple of weeks. Despite the uncertainty, fairly confident that
temperatures will be well below normal for the end of next week
with the cooler air mass around. One thing that this low should do
in either scenario is dissolve the marine inversion which could
actually result in more sunshine than what we have seen over the
last few days, despite the chance of rain. As a result, the
cooling will likely be mostly felt away from the coast.

&&

.AVIATION...20/1757Z.

At 1715Z, the marine inversion at KLAX was based at 2400 feet.
The top of the inversion was 4200 feet with a temperature of 15
deg C.

Overall for 18Z TAF package, high confidence in desert TAFs and
moderate in coastal/valley TAFs. Current MVFR/IFR conds are
expected to dissipate by early this afternoon, but timing could be
+/-1 hours of current forecasts. For tonight, hi confidence in
CIG/VSBY restrictions moving back into coast/vly airfields S of
Point Conception, with generally VFR conds N of Point Conception.

KLAX...Moderate confidence in 18Z TAF. Timing of dissipation of
MVFR CIGs could be +/- 1 hour of current 22Z forecast. For
tonight, high confidence in return of MVFR conds, but low
confidence in timing (could be +/- 1-2 hours of current 03Z
forecast). No significant easterly wind component is expected.

KBUR...Moderate confidence in 18Z TAF. Timing of dissipation of
MVFR CIGs could be +/- 1 hour of current 20Z forecast. For
tonight, there is a 50%-60% chance that MVFR conds moving back
into the airfield aft about 08Z, with the timing off +/- 1-2
hours.

&&

.MARINE...20/120 PM.

For the Outer Waters, high confidence in current forecast. Through
Sunday night, Small Craft Advisory (SCA) level winds and choppy
seas are expected, generally north of San Nicolas Island with the
most widespread winds across PZZ670/673. For Monday through
Wednesday, winds and seas will remain below SCA levels, then there
is a 40%-50% chance of SCA wind gusts at times for Thursday.

For the Inner Waters north of Point Sal, high confidence in
current forecast. SCA level winds are expected in the afternoon
and evening hours both through Sunday. For Monday through
Thursday, winds and seas will remain below SCA levels.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. For most of the southern waters,
high confidence in winds and seas remaining below SCA levels
through Thursday. The only exception will be the western half of
the Santa Barbara Channel where there is a 50-60% chance of SCA
level winds Monday night and a 40%-50% chance of these winds
again on Thursday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Monday for zone
      645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 6 AM PDT Monday for
      zones 670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect from 9 PM this evening to 6 AM
      PDT Sunday for zone 676. (See LAXMWWLOX).

&&

$$

PUBLIC...Kittell
AVIATION...Sirard
MARINE...Sirard
SYNOPSIS...Kittell

weather.gov/losangeles

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