720
FXUS66 KLOX 180533
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1033 PM PDT Fri May 17 2024

.SYNOPSIS...17/813 PM.

A persistent marine layer will remain in place through the
weekend as strong onshore flow continues across the area. Night
through morning low clouds and fog will continue to be a staple of
the forecast, struggling to clear from the coast each afternoon.
Breezy to gusty onshore winds will occur across the interior
valleys and adjacent foothill areas each afternoon and evening.
Better clearing with slight warming is possible next week as
onshore flow could weaken.

&&

.SHORT TERM (FRI-MON)...17/813 PM.

A long wave trough embedded along the West Coast will remain
in place through early next week, maintaining a strong onshore
flow and deep marine layer pattern. The current marine layer
depth is around 3500 feet across the LA Basin, with low clouds
already reaching the lower coastal slopes this evening. The LAX-
DAG gradient is expected to remain strong through Monday,
generally ranging in the +8 to + 10 mb range each afternoon. This
will translate into gusty onshore winds across the interior, with
gusts of 25 to 35 mph common, and isolated gusts as high as 45
mph in the foothills of the Antelope Valley (which may need a wind
advisory at times this weekend). We have seen isolated gusts of
around 45 mph near Lake Palmdale for the past few hours. With
the marine layer so deep, we may see some patchy morning drizzle
through the weekend, with the possibility of reverse clearing
(where coastal areas may see better clearing than the interior).
Temperatures will remain at least 3-6 degrees below normal and
possibly more where clouds linger most of all of the day.

*** From previous discussion ***

On Monday the trough will deepen along the coast and also pull in
a secondary upper low to our southwest that has been slowly
working its way eastward. This will likely deepen the marine layer
further with possibly more extensive drizzle during the morning
hours and lower chances for afternoon clearing.

For far interior areas skies will generally remain clear, though
can`t rule out some stratus making into parts of the Antelope
Valley, interior SLO County and the Cuyama Valley. Temperatures
there will be a few degrees above normal through the period.
Gusty west to southwest winds likely each afternoon.

.LONG TERM (TUE-FRI)...17/200 PM.

There is still good model and ensemble agreement on a significant
weakening of the onshore flow Tue/Wed following the passage of the
persistent long wave trough along the West Coast. NAEFS and
deterministic pressure gradients all showing onshore flow
weakening 3-4mb Tuesday with the flow aloft shifting to the north-
northwest. This should promote much earlier marine layer clearing
and 4-8 degrees of warming, especially in the coastal valleys.

This may be short-lived though as models are showing yet another
upper low dropping out of the Pac NW Thu/Fri that will likely pus
southwest California right back into the deep marine layer
pattern. And it looks like that will remain through the following
weekend.

&&

.AVIATION...17/2351Z.

At 2350Z at KLAX, the marine layer was 3000 ft deep. The top of
the inversion was 5400 feet with a temperature of 20 C.

Overall for the 00Z TAF package, high confidence for desert TAFs
and moderate confidence in coastal/valley TAFs. Lower confidence
for coastal/valley sites due to uncertainties with flight category
changes with the marine layer stratus.

KLAX...Moderate confidence in 00Z TAF. MVFR to VFR cigs expected
through much of the forecast period. Any east wind component
on Saturday morning is expected to be 6 kt or less. There is a
20 percent chance of clearing on Saturday afternoon.

KBUR...Moderate confidence in 00Z TAF. MVFR cigs expected through
early Saturday afternoon. There is a 20 percent chance of no
clearing on Saturday afternoon.

&&

.MARINE...17/1033 PM.

For the Outer Waters, generally high confidence in current
forecast. Tonight through Saturday, winds and seas will remain
below Small Craft Advisory (SCA) levels. On Sunday, SCA level
winds will develop across PZZ670 then spread into PZZ673/676
Monday through Wednesday with the potential for SCA level seas
also.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. Tonight through Saturday, high
confidence in winds and seas remaining below SCA levels. For
Sunday through Wednesday, there is a 50% chance of SCA level
winds in the afternoon and evening hours.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. For a majority of the area, high
confidence in winds and seas remaining below SCA levels tonight
through Wednesday. However across the western half of the Santa
Barbara Channel, there is a 30-40% chance of SCA level winds
Monday through Wednesday, mainly in the late afternoon and evening
hours.

&&

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

&&

$$

PUBLIC...Gomberg/MW
AVIATION...Gomberg
MARINE...Phillips/RAT
SYNOPSIS...Hall

weather.gov/losangeles

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