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000
FXUS66 KLOX 232138
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
238 PM PDT Tue Apr 23 2024

.SYNOPSIS...23/122 PM.

Strong onshore flow and a deep marine layer will maintain much
cooler than normal temperatures through at least Friday. Areas of
night and morning fog and drizzle are expected across the coast,
valley, and foothill areas with only partial afternoon clearing.
Warmer weather is expected by the weekend into early next week.

&&

.SHORT TERM (TDY-FRI)...23/147 PM.

No significant changes to the forecast today as a series of low
pressure systems move through California through Friday. Cooling
aloft associated with these upper lows has deepened the marine
layer to around 5000 feet while onshore flow to the east is
approaching 9mb this afternoon. Today saw our first day of reverse
clearing of the marine layer and this may be the case again
Wednesday as well. With a little more sunshine today many coastal
area temperatures were a couple degrees warmer than the previous
couple days, but still well below normal. Some breezy winds have
developed through the I14 corridor and into the Antelope Valley
with that strong onshore flow but with the exception of the usual
Lake Palmdale station winds are below 40 mph and expected to
remain that way through early Thursday.

There is low confidence in how the marine layer will behave
Wednesday now that the it`s so deep. The most likely outcome is
another day very similar to today, with (not so) low clouds
reforming overnight in most areas then another reverse clearing
pattern tomorrow. Most of the high res forecast models favor this
scenario along with some pockets of drizzle, especially near the
south facing foothills. However, the next upper low will be
quickly approaching the area Wednesday with an arrival expected
Wednesday night into Thursday. So some additional cooling aloft is
expected that could either reinforce the marine layer or
potentially weaken it enough to where it clears out more
completely in the afternoon. In any case, temperatures will
remain well below normal with some breezy but again sub-advisory
level winds across interior areas.

With the arrival of the upper low Wednesday night into Thursday
morning, chances for more widespread drizzle or light rain
increase. But with northwest flow following the trough passage
Thursday afternoon that should help generate better clearing.
Increasing west to northwest winds expected in the afternoon and
evening with wind advisories possible for some coastal areas and
interior areas as well.

Yet another trough quickly follows for Friday, though models
have been tracking this one more inland. Temperatures will remain
on the cool side with some gusty west to northwest winds but
minimal chances for precip, except possibly across the northern
mountains and interior SLO County. Still low confidence in the low
cloud coverage but the most likely outcome is for less clouds
across coast and valleys. Temperatures will remain below normal
but should be 3-6 degrees warmer than Thursday.

.LONG TERM (SAT-TUE)...23/153 PM.

The warming trend that started Friday is expected to continue into
early next week with weakening onshore flow and minimal, if any,
marine layer stratus. Temperatures should be back to normal
levels over the weekend and sneaking a few degrees above normal by
Monday. Some cooling then expected Tuesday that will likely
continue through the rest of next week as yet another cold upper
low drops out of the Pac NW.

&&

.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...23/236 PM.

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 Sunday, high confidence in combination of SCA
level winds and seas. Across the two southern outer water zones
(PZZ673/676), there is a 50-60% chance of Gale force winds
Thursday and 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. For
Saturday and Sunday, 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 morning,
high confidence in winds and seas remaining below SCA levels,
expect for a 60% chance of SCA level winds for the SBA Channel
this evening/night. Wednesday afternoon/night, there is a 60-80%
chance of SCA level winds for all the southern inner waters. Winds
will pick back up Thursday morning for the SBA channel (with a
20-30% chance of Gale force winds on Thursday), and reaching the
waters south of Point Mugu Thursday afternoon. SCA wind or seas
will last much of the time Thursday through Saturday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 9 PM this evening to 9 AM
      PDT Wednesday for zone 650. (See LAXMWWLOX).

&&

$$

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

weather.gov/losangeles

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