363
FXUS66 KLOX 172101
AFDLOX

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

.SYNOPSIS...17/103 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 (TDY-MON)...17/148 PM.

A long wave trough embedded along the West Coast will remain more
or less in place into early next week. This will maintain a
favorable scenario for a deep marine layer, areas of morning
drizzle, and slow if any clearing for coast and coastal valleys,
especially south of Pt Conception. One caveat to that is today
there were signs of a reverse clearing pattern setting up where
clouds cleared first over the coastal waters. With some further
deepening of the marine layer possible the next couple nights,
this trend may grow to encompass more of the coastal areas and
possibly parts of the coastal valleys. So, the upshot of that is
there is low confidence regarding the clearing potential this
weekend. Either way, temperatures will remain at least 3-6 degrees
below normal and possibly more where clouds linger most of all of
the day.

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...17/1759Z.

At 1735Z at KLAX, the marine layer was 2800 ft deep. The top of
the inversion was 5400 feet with a temperature of 17 C.

Overall for the 18Z 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 18Z TAF. There is a 40% chance that
MVFR CIGs do not dissipate this afternoon. Timing of return of
MVFR CIGs this evening could be +/- 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 this afternoon could be +/- 1 hour of current 21Z
forecast. For tonight, timing of return of MVFR CIGs could be +/-
2 hours of current 05Z forecast.

&&

.MARINE...17/1242 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 Monday, high
confidence in winds and seas remaining below SCA levels. For
Tuesday and 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...MW
AVIATION...RAT
MARINE...RAT
SYNOPSIS...Hall

weather.gov/losangeles

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