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896
FXUS66 KLOX 210319
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
819 PM PDT Mon May 20 2024

.SYNOPSIS...
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20/817 PM.

Low clouds will continue through the morning with better clearing
on Tuesday afternoon. 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.
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&&

.SHORT TERM (MON-THU)...
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20/818 PM.

An upper level trough will continue to dig into the Great Basin
tonight into Tuesday. This system will generate some gusty
northwest to north winds tonight, with the low level flow shifting
to the northeast on Tuesday morning across the mountains and
Antelope Valley. The wind advisory for the Antelope Valley
foothills has been cancelled early as winds are already beginning
to diminish as onshore pressure gradients gradually weaken
tonight. The strongest northwest to north winds tonight will be
focused across the I-5 corridor and Southwest Santa Barbara county
where wind gusts of 30 to 40 mph will be common. As the flow
turns northeast on Tuesday morning, looking for some wind gusts of
20 to 30 mph in the mountains of LA/Ventura counties.

With a weakened inversion tonight, the marine layer cloud coverage
is quite chaotic. But in general, low clouds are expected to fill
in across many coastal/valley areas overnight into Tuesday
morning, although the marine layer depth is expected to gradually
diminish (especially north of Point Conception). Low clouds are
expected to be confined to just coast and coastal valley areas
Tuesday night into Wednesday morning. For Wednesday night and
Thursday, looks like the stratus will make a renewed push inland
to the lower coastal slopes. Other than the marine layer stratus,
skies should remain mostly clear through the period.

*** From previous discussion ***

As for temperatures, will expect a warming trend for all areas
Tuesday and Wednesday with rising thicknesses and less marine
influence. So, coastal valley areas will experience temperatures
in the 70s through Wednesday. For Thursday, temperatures will drop
a few degrees for all areas.

.LONG TERM (FRI-MON)...20/200 PM.

For the extended, models and their various ensembles are in
decent agreement through the period. A broad upper level trough
will persist over the area Friday/Saturday, but a rather flat
upper level ridge will begin to build on Sunday/Monday.

Forecast-wise, marine layer stratus will continue to be the main
challenge through the period. For Friday/Saturday, expect the
marine inversion to remain rather deep, with stratus pushing into
the coastal slopes and slow afternoon clearing. This significant
marine layer pattern and upper level trough will keep all areas a
few degrees cooler than normal through Saturday. Also, moderate to
strong onshore gradients will keep the potential for some advisory
level southwesterly winds across interior sections each afternoon
and evening, especially in the Antelope Valley foothills.

For Sunday/Monday, increasing H5 heights will help to smoosh the
marine inversion, with decreasing inland penetration each night.
Also with rising thicknesses and less marine influence, a warming
trend can be expected for all areas.
-- End Changed Discussion --

&&

.AVIATION...21/0110Z.

At 0030Z at KLAX, the marine layer was 3700 ft deep. The top of
the inversion was at 5400 feet with a temperature of 13 C.

Good confidence in desert TAFs.

Moderate confidence in cigs returning to most coastal/valley
TAF sites but timing could be +/- 3 hours from TAF timing.
With weakening onshore flow tonight, and a weak offshore flow
across the interior on Tuesday morning, looking for cigs
to be somewhat lower than today. Areas south of Point Conception
should stay mostly in MVFR category, but KSMX and KSBP likely
to lower to IFR category tonight. Look for earlier clearing
on Tuesday.

KLAX...Moderate confidence in TAF. High confidence in VFR
conditions through early evening, with MVFR cigs expected
to return +/- 3 hours from TAF timing of 06z. Any easterly
wind component on Tuesday morning is expected to be 5 knots
or less.

KBUR...SCT-BKN030-040 conditions through this evening, with
higher probability of MVFR cigs returning overnight into
early Tuesday morning. Timing of cigs expected to be +/-
3 hours from TAF timing of 09z.

&&

.MARINE...20/101 PM.

High confidence in Small Craft Advisory (SCA) seas and/or
northwest winds continuing over the offshore waters from the
Central Coast to San Nicolas Island through at least Tuesday and
likely beyond. There will likely be brief and slight lulls each
morning. There is a 30 percent chance of SCA for the western
Santa Barbara Channel each evening. SCA conditions are unlikely
elsewhere. Fairly large seas will continue as a result, with
short period dominant seas over most nearshore waters.

A long period south to southwest swell will diminish into Tuesday.
The than usual breaking waves nearshore as well as some stronger
currents near most harbor entrances through this evening will
likewise diminish into Tuesday.

&&

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

&&

$$

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

weather.gov/losangeles

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