Area Forecast Discussion
Issued by NWS Los Angeles, CA

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729
FXUS66 KLOX 171800
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1100 AM PDT Fri May 17 2024

.SYNOPSIS...17/943 AM.

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-SUN)...17/949 AM.

***UPDATE***

A persistent marine layer pattern with strong onshore flow will
continue through the weekend as a long wave trough remains along
the West Coast. Clearing will be slow or non-existent for coast
and valleys with temperatures 4-8 degrees below normal, the
valleys being on the higher side of that range. Interior areas
will remain clear but breezy with highs 2-5 degrees above normal.

***From Previous Discussion***

Weak dynamics with the upper-level trough will start to scrape
the area tonight and into Saturday morning. The dynamics with the
trough will likely lift the marine layer induced cloud deck and
squeeze out some drizzle. PoPs were nudged higher tonight through
Saturday morning to account for the drizzle possibility. While it
is less confident, there is an outside chance that mountains
showers could develop on Saturday afternoon and evening, but most
model solutions suggest the middle-levels of the atmosphere to be
too dry at this time.

Strong onshore pressure gradients will likely bring breezy to
gusty onshore winds each day across the high valleys and interior
portions of the area and into the adjacent foothill areas. Winds
appear to remain below advisory levels again today, but winds are
expected to increase on Saturday and Sunday. At this time,
advisory levels could occur across the Antelope Valley and
adjacent foothill areas. A wind advisory may be issued later to
account for gusty southwest winds in places, such as Lake Palmdale
and Sierra Pelona. At the very least, elevated fire weather
conditions will continue across the interior portions of the area,
such as the Antelope Valley this afternoon and evening where
winds could combine with drier conditions to bring elevated fire
weather conditions.

.LONG TERM (MON-THU)...17/337 AM.

EPS cloud cover means suggest better clearing after Monday as an
upper-level trough digs south down the state. Cold air advection
moving south with a decaying frontal boundary could transport
enough colder air to weaken the marine inversion. Thus, confidence
continues to grow for temporary break of May Gray for the early
half of next week. GEFS ensemble pressure gradients suggest
onshore pressure gradients weakening for Tuesday and Wednesday.
The weakening onshore gradients should promote an earlier
clearing of the marine layer stratus for the coastal and valley
areas. Gusty northerly winds will be possible across southern
Santa Barbara County and through the Interstate 5 Corridor during
evening and morning hours between Monday night and Wednesday
morning. The forecast still takes a conservative approach for
next week as there is a spread of the possible outcomes in the
forecast ensembles for Tuesday and Wednesday, but if the ensembles
continue to trend this direction, the changes to the forecast
should occur and a warming trend with less clouds should be
expected.

&&

.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...17/335 AM.

In the Outer Waters, rather high confidence in the forecast.
Small Craft Advisory (SCA) conditions are not expected thru
Sun. There is a 30-40% chance of SCA winds/seas in the outer
waters Sun night/Mon, and SCA conds are likely Tue.

For the Inner Waters N of Pt. Sal, high forecast confidence.
Winds and seas are expected to remain below SCA levels thru
Mon night, with a 20-30% chance of SCA winds Tue.

In the Inner Waters S of Pt. Conception, moderate to high
forecast confidence. There is a 20-30% chance of SCA level winds
in western portions of the SBA Channel in late afternoon/eve
hours Mon and Tue. Otherwise, SCA conds are not expected.

&&

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

&&

$$

PUBLIC...MW/Hall
AVIATION...RAT
MARINE...DB
SYNOPSIS...Hall

weather.gov/losangeles

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