LA Area Forecast Discussion

000
FXUS66 KLOX 231046
AFDLOX

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

.SYNOPSIS...23/227 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. 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 light rain showers, but more
likely just more drizzle. Clearing skies are forecast for the
weekend.

&&

.SHORT TERM (TDY-THU)...23/304 AM.

An early preview of June Gloom is on tap for the next three days
as a deep marine layer, onshore flow and an approaching trof all
conspire to keep a marine stratus deck intact over the csts and
most vlys through the three day period.

Currently the marine layer is 2700 ft deep and the onshore push to
the N is 5 mb and the push to the E as 6 mb at the afternoon
diurnal max these values should be near 6 mb to the north and 9
mb to the E. Much like Monday there will be some morning drizzle
and limited or no afternoon clearing. Max temps will not change
much across the csts, the vlys will fall 3 to 6 degrees but the
cooler air will infiltrate the interior and bring 6 to 12 degrees
of cooling. Max temps today will end up 6 to 12 degree blo
normals. The strong onshore push will bring gusty just below
advisory winds to the interior esp the Antelope Vly. The coasts
will experience a stronger and later lasting sea breeze.

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...23/1045Z.

At 1030Z, the marine inversion at KLAX was based at 3500 feet.
The top of the inversion was 4800 feet with a temperature of
12 degrees Celsius.

Overall for 12Z TAF package, 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 a 40% chance of some
afternoon clearing at sites with no clearing forecast and also a
40% chance of no afternoon clearing at sites with a clearing
forecast.

KLAX...Moderate confidence in 12Z TAF. There is a 40% chance of
IFR CIGs 12Z-17Z. There is a 30-40% chance that MVFR CIGs will
dissipate 20Z-04Z. No significant easterly wind component is
expected.

KBUR...Moderate confidence in 12Z TAF. There is a 40% chance of
IFR CIGs 12Z-17Z. There is a 30% chance that MVFR CIGs will not
dissipate this afternoon.

&&

.MARINE...23/1248 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...Rorke
AVIATION...RAT
MARINE...RAT
SYNOPSIS...Cohen

weather.gov/losangeles

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

NWS LOX Office Area Forecast Discussion