446
FXUS66 KLOX 200319
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
819 PM PDT Sun May 19 2024

.SYNOPSIS...19/816 PM.

Low clouds will continue to be a staple of the forecast for coast
and valleys through Monday, and struggling to clear each
afternoon. Breezy onshore winds will occur across the interior
valleys and adjacent foothill areas each afternoon and evening.
More sunshine with slight warming is expected Tuesday and
Wednesday as onshore flow weakens. Then cooler with increasing
marine layer clouds again the latter half of next week.

&&

.SHORT TERM (SUN-WED)...19/812 PM.

A persistent long wave trough along the West Coast coupled with
strong onshore flow will continue to maintain a deep marine layer
with cooler than normal temperatures through Monday for coast and
coastal valleys. Current satellite imagery showing rather chaotic
cloud pattern. With upper level trough passing to the north
tonight, there will be lowering heights across the region. This
combined with the strong onshore flow is expected to bring further
deepening of the marine layer. Current ACARS data is showing
a marine layer depth around 3200 feet across the LA Basin, and
could reach 4000 feet by Monday morning. As a result, expecting
to see areas of drizzle by Monday morning. In evening update,
have introduced a 10-20 percent chance of measurable light rain,
with highest chances across LA county and the Central Coast.
The deepening mariner layer combined with strong onshore flow
pattern is generating onshore wind gusts of 25 to 40 mph across
interior areas today, with isolated gusts as high as 50 mph
possible in the Antelope Valley foothills. The wind advisory
in effect for the Antelope Valley and western foothills will
expire at 9 pm as winds will begin to gradually diminish
overnight. Conditions are favorable for a slight uptick in onshore
winds across the Antelope Valley and adjacent western foothills
is expected on Monday afternoon/evening, and will likely require
another wind advisory.

*** From previous discussion ***

Clearing was somewhat more complete across LA
County today than the last few days but similar or slower
elsewhere. Tonight and Monday morning is expected to be similar to
the last several nights and mornings. However, after that models
continue to indicate the trough starting to shift east Monday with
some northerly flow aloft developing along with the beginnings of
a downward trend in onshore flow. This should promote earlier
clearing of the marine layer Monday afternoon, though clouds may
continue along the coast much of the afternoon. Temperatures may
warm a degree or two Monday across the valleys with the earlier
clearing.

Gradients continue to weaken Tue and Wed with slow rising of
heights and thicknesses. The much weaker onshore flow and earlier
marine layer clearing will help warm up the valleys several
degrees from recent days with highs in the mid to high 70s and
around a 40% chance of low 80s in the warmest locations. Warmer at
the coast as well with some lower 70s likely away from the
beaches. There will even be a light northeast breeze across the
inland valleys and mountains Tuesday morning into early afternoon,
though well below advisory levels.

.LONG TERM (THU-SUN)...19/203 PM.

After a two day reprieve Tue/Wed, troughing and strong onshore
flow returns later in the week through next weekend. The marine
layer is likely to deepen to at least 3000 feet again by Saturday,
if not sooner, with slow or minimal clearing for coast/valleys and
possibly some morning drizzle. High temperatures will fall back to
the mid to 60s across most coast/valleys. Clear skies expected for
mountains and desert areas but cooler there as well with gusty
onshore winds at times.

&&

.AVIATION...20/0008Z.

At 2355Z at KLAX, the marine layer was 3200 ft deep. The top of
the inversion was at 4800 feet with a temperature of 16 C.

Good confidence in desert TAFs.

MVFR cigs lingered this afternoon at KSMX, KSBA, KOXR, and KCMA.
Low clouds expected to fill in quickly across remaining
coast/valley TAF sites tonight, mostly with MVFR cigs. Marine
layer depth is expected to rise to around 4000 feet by
Monday morning, with low clouds surging well into the coastal
slopes. There will likely be areas of drizzle with a 10 percent
chance of measurable light rain, mainly for coastal/valley areas
south of Point Conception. MVFR cigs expected across most TAF
sites tonight into Monday morning, potentially lingering across
coastal TAFS into the afternoon hours on Monday.

KLAX...Moderate confidence in TAF. MVFR cigs expected to arrive
+/- 2 hours of TAF timing of 02z and then persist through Monday
morning, with a 30 percent chance of cigs lingering into Monday
afternoon. A weak eddy circulation will bring the potential
for a 4-6 knot easterly wind component on Monday morning.

KBUR...Moderate confidence in TAF. MVFR cigs expected to arrive
+/- 2 hours of TAF timing of 07z and then persist through Monday
morning, with a 20 percent chance of cigs lingering into Monday
afternoon.

&&

.MARINE...19/819 PM.

High confidence in Small Craft Advisory (SCA) seas and/or
northwest winds forming tonight over the offshore waters from the
Central Coast to near the Channel Islands with moderate confidence
of extending to San Nicolas Island. There is a 30 percent chance
of SCA for the western Santa Barbara Channel each evening. These
conditions will continue through Monday and likely beyond. Seas
will be building everywhere as a result, with short period
dominant seas over most nearshore waters by Sunday Night or
Monday. SCA conditions are unlikely elsewhere. Southeast winds
will form each morning over the nearshore waters from Santa
Barbara to Orange County starting Monday or Tuesday. These winds
may enhance to near 15 knots through passages and channels.

A long period south to southwest swell will peak Sunday and Monday
with heights of 2 to 4 feet. This will create larger than usual
breaking waves nearshore as well as some stronger currents near
most harbor entrances.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect through Monday evening for
      zones 87-362-366. (See LAXCFWLOX).
     Wind Advisory in effect until 9 PM PDT this evening for zones
      381-383. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Tuesday for
      zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Gomberg/MW
AVIATION...Gomberg
MARINE...Kittell/RM
SYNOPSIS...MW

weather.gov/losangeles

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