-- Discussion containing changed information from previous version are highlighted. --
759
FXUS66 KLOX 210714
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1214 AM PDT Tue May 21 2024

.SYNOPSIS...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.

&&

.SHORT TERM (TUE-FRI)...
-- Changed Discussion --
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 (SAT-TUE)...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...
-- Changed Discussion --
21/0713Z.

At 0505Z at KLAX, the marine layer was 3200 ft deep. The top of
the inversion was at 4800 feet with a temperature of 13 C.

Good confidence in desert TAFs.

Low confidence in TAF for KSBA with a 40 percent chc of MVFR cigs
11Z-18Z.

Moderate confidence in TAFs. VFR transitions could be off by +/-
90 minutes. Lower confidence in return of low clouds after 22/03Z
with near equal chances of an earlier or much later arrival time.

KLAX...Moderate confidence in TAF. VFR transition could occur any
time between 18Z and 21Z. Low confidence in timing of return of
low clouds Tuesday evening with a 30 percent chc of an arrival
time 10Z-11Z and a 20 percent chc of 07Z-08Z. Good confidence that
any east wind component will be 5 knots or less.

KBUR...Moderate confidence in TAF. VFR transition may be as late
as 20Z. There is a 30 percent chc that cigs will not drop below
OVC022. There is a 25 percent chc of no low clouds Tuesday
evening.
-- End Changed Discussion --

&&

.MARINE...20/932 PM.

High confidence in the current forecast. Widespread Small Craft
Advisory (SCA) conditions (winds and seas) will continue over the
offshore waters from the Central Coast to San Nicolas Island
through at least late Tuesday night and likely through at least
Friday. There will likely be brief and slight lulls during the
late night and morning hours. There is a 30-50 percent chance of
SCA winds for the western Santa Barbara Channel and into the
nearshore waters along the Central Coast each afternoon and
evening. SCA conditions are unlikely elsewhere.

A long period south to southwest swell will diminish late Tuesday
night and into Wednesday. 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 Wednesday afternoon
      for zones 87-362-366. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Wednesday for
      zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Gomberg/Thompson
AVIATION...Rorke
MARINE...Hall
SYNOPSIS...Gomberg

weather.gov/losangeles

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