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000
FXUS66 KLOX 231829
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1129 AM PDT Tue Apr 23 2024

.SYNOPSIS...23/839 AM.

Strong onshore flow and a deep marine layer will bring low
clouds and patchy fog and drizzle to the coast and coastal
valleys throughout this week with partial afternoon clearing.
Cool conditions will continue, with high temperatures several
degrees below normal each day this week. A couple of weather
disturbances will track across the area as well, bringing a small
chance for drizzle or light rain showers. Warmer weather is
expected by the weekend.

&&

.SHORT TERM (TDY-THU)...23/851 AM.

***UPDATE***

Pilot reports and soundings are indicating the marine layer depth
has reached a remarkable 5000 feet today. Meanwhile, onshore
gradients to the east have risen to 6mb. So it`s going to be
another cool day across the area. However, satellite imagery is
showing quite a bit of thinning of the cloud layer with numerous
breaks in the overcast so it appears likely that many areas will
see a fair amount of sunshine by afternoon, if not sooner. That
alone should bring temperatures up a few degrees, but still well
below normal. In these deep marine layer patterns often the
clearing pattern is best described as going in reverse, meaning
it clears near and over the ocean first, then works its way inland
through the afternoon, but it doesn`t always make it all the way.
So inland areas, particularly near the south facing mountains,
will have a harder time clearing.

Despite the likely appearance of sunshine today, the overall
pattern for the week remains cool with lots of marine layer
stratus. There remains at least a 20-30% chance of drizzle or
light rain at times. Best chances for that would appear to be late
Wednesday into Thursday when the primary trough moves through the
area.

***From Previous Discussion***

Tonight and Wednesday will not look too much different from today
as all most all weather parameters look similar. There is a
little less onshore flow to the north so its possible that some
inland vlys like Ojai and Santa Clarita will see earlier or better
clearing.

On Thursday a weak trof will move through the state. By itself
this trof will not produce rain, but when it interacts with and
lifts the marine layer it could produce some light rain esp near
the foothills. More likely it will just produce more drizzle -
either way many people will likely need their wipers during the
morning commute. There is a smaller chance the the capping
inversion will be lifted and mixed out which will cause most of
the low clouds to simply dissipate. The marine layer clouds
should dissipate in the afternoon in the wake of trod as cooler
and mixing should eliminate the marine clouds. The return of
afternoon sunshine should overwhelm the limited cool air advection
behind the trof and max temps should rise 2 to 5 degrees across
most locations. Max temps will still end up 5 to 10 degrees blo
normal with max temps across the csts/vlys only in the 60s.

.LONG TERM (FRI-MON)...23/319 AM.

Low confidence in the Friday morning fcst. There is a good chance
that the marine inversion will not reform and skies will be mostly
clear. But there is a second little piece of energy coming in over
the area and the ensembles are trending to another round of low
clouds and perhaps some more drizzle. Still the mdls seem to be
trending towards a less dynamic system and would not be surprised
to see this fcst change. Better confidence in 2 to 3 degrees of
warming with ample afternoon sunshine and rising hgts.

Then just in time for the weekend a ridge arrives along with
weaker onshore flow or evening weak offshore flow. There will be
only limited marine layer clouds and warming each day Saturday
through Monday. A few sites will see above normal temps on Sunday
and many locations will be above normal on Monday when max temps
will mostly be in the 70s and lower 80s across the csts and vlys.

&&

.AVIATION...23/1829Z.

At 1744Z at KLAX, the marine inversion was based at 3700 feet.
The top of the inversion was 4500 feet with a temperature of 11 C.

Low to moderate confidence for coastal/valley TAFs and high
confidence for desert TAFs. Lower confidence for coastal/valley
sites due to uncertainties in timing of flight category changes.
There is 30% chance of no afternoon clearing at sites with a
clearing forecast.

KLAX...Moderate confidence, due to uncertainty in timing of cig
arrival and dissipation. No significant easterly wind component
is expected.

KBUR...Moderate confidence, due to uncertainty in timing of cig
arrival and dissipation.

&&

.MARINE...23/845 AM.

For the Outer Waters, moderate to high confidence in current
forecast. Today through Wednesday night, high confidence in winds
and seas remaining below Small Craft Advisory (SCA) levels. For
Thursday through Saturday, high confidence in combination of SCA
level winds and seas. Across PZZ673/676, there is a 40-50% chance
of Gale force winds Thursday afternoon/night and a 20-30% chance
Friday afternoon/night.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. Today through Wednesday night,
high confidence in winds and seas remaining below SCA levels.
For Thursday through Friday, there is a 60-80% chance of SCA level
winds, especially in the afternoon and evening hours. On Saturday,
there is a 40-50% chance of SCA level winds, especially in the
afternoon and evening hours.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. Today through Wednesday night,
high confidence in winds and seas remaining below SCA levels. For
Thursday through Saturday, there is a 60-80% chance of SCA level
winds with the strongest winds across western sections.

&&

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

&&

$$

PUBLIC...MW/Rorke
AVIATION...Schoenfeld
MARINE...RAT/Schoenfeld
SYNOPSIS...MW/Cohen

weather.gov/losangeles

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