342
FXUS66 KLOX 200312
AFDLOX
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
812 PM PDT Sat Sep 19 2026
.SYNOPSIS...19/736 PM.
A weak upper level trough will move over the area this weekend
into Monday, cooling temperatures slightly and increasing marine
layer stratus. A warming trend will begin Tuesday and peak on
Thursday, with highs 5 to 10 degrees above normal.
&&
.SHORT TERM (SAT-TUE)...19/808 PM.
***UPDATE***
High clouds are just starting to stream into the region thanks to
a trough moving over the area. Closer to the surface, marine layer
clouds are already starting to spread across the Central Coast,
and one little blob extending into a very small section of
the Ventura County Coast. Expecting these clouds to extend into
the coastal valleys overnight, and may be slow to burn off late
morning.
High clouds will continue into tomorrow, and slightly lower
temperatures are forecast compared to today, but still in the 70s
and 80s. Little moisture is associated with the upper level
trough, however there is some instability over the higher
elevation mountain areas, mainly for Santa Barbara and Ventura
counties. As a result, there is a 5to 10 percent chance of
thunderstorms/showers during late Sunday into Monday. Due to the
lack of sufficient moisture, little to precip accumulation is
expected, and the main risk should a thunderstorm form, would be
dry lightning.
No big changes were needed in the evening forecast update.
***From Previous Discussion***
Temperature trends were generally flat today, except for areas
above 1200 feet elevation where some places warmed as much as 10
degrees. Expecting a little cooling Sunday as a weak upper low
over the eastern Pacific moves closer to the Central California
coast and onshore flow increases. Will probably see more in the
way of morning low clouds and fog and lingering a little deeper
into the morning hours Sunday. And in turn likely a degree or two
cooler overall for coast and valleys. Farther inland areas will
see little change. There is a little elevated cape tomorrow
afternoon but PW`s are under .75" and also confined to very high
altitudes. Wouldn`t be surprised to see some high based clouds
over the SB/Ventura mountains but very little chance of any precip
reaching the ground.
As the low moves inland Monday heights will lower and temperatures
will cool, especially far inland areas where highs will be 4-8
degrees cooler (and 4-8 degrees below normal) with some
increasing afternoon sea breezes. Chances for any showers or
thunderstorms will be a little higher than Sunday with the low
pretty much right overhead. However, moisture remains very limited
and chances for any reaching the ground remain below 10% and
mostly confined to the mountains. Most likely just some afternoon
build ups over the mountain peaks. Otherwise, for coast and
valleys just a typical morning marine layer that will clear by
late morning with highs 1-3 degrees cooler than Sunday.
A little recovery in high temps Tuesday but most areas (except the
immediate coast) remaining 3-6 degrees below normal.
.LONG TERM (WED-SAT)...19/227 PM.
Most of the warming next week is going to be on Wednesday after
the low finally exits and higher pressure develops over the Pac NW
resulting in a weaker onshore flow and less marine layer
influence. The biggest temperature jumps Wednesday will be in the
coastal valleys where highs will be in the 90s with around a 20%
chance of 100 degrees in the western San Fernando Valley, rising
to 50-60 chance of 100 or higher across inland SLO and Santa
Barbara Counties. Coastal and intermediate areas will warm up as
well with most areas in the high 70s to mid 80s, with a 20-30%
chance of 90 degrees in Downtown LA as early as Wednesday or
Thursday.
Temperatures will trend cooler later next week across northern
areas, as the trough pattern returns over the eastern Pacific.
Less confidence in cooling temps in the south due to the
uncertainty with the trough position, and it`s possible that
Wednesday`s temps will continue into next weekend.
&&
.AVIATION...20/0046Z.
At 0015Z at KLAX, the marine layer was 1400 ft deep. The top of
the inversion was at 2600 ft with a temperature of 22 C.
High confidence in VFR conds for KPMD & KWJF.
Low to moderate confidence in the remaining sites. The timing of
CIG and any VSBY restrictions tonight into Sun morning may be off
+/- 2 hrs and flight minimums by one category.
KLAX...Low to moderate confidence in TAF. Flight cat changes may
be off by +/- 3 hours, and cigs may scatter and reform due to
high clouds after 08Z Sun. Any east wind component is expected
remain less than 6kt.
KBUR...Moderate to high confidence in TAF. Flight cat changes may
be off by +/- 2 hrs from forecast times.
&&
.MARINE...19/811 PM.
For the outer waters, high confidence in the current forecast.
Small Craft Advisory (SCA) level winds are likely across most of
the waters through Sunday morning, then for the waters mainly
west and northwest of Point Conception Sunday through Sunday or
Monday night. The SCA winds will be most persistent around Point
Conception. There is a 40%-50% chance of SCA wind gusts west and
south of Point Conception Tuesday afternoon and night as well,
otherwise conds will be below SCA levels Tuesday through Thursday
night. Expect steep, choppy seas with the SCA conditions.
For the inner waters N of Point Sal, moderate to high confidence
in the current forecast. SCA wind gusts are likely during the
afternoons and evenings through Sunday and again Tuesday. Conds
are otherwise expected to be below SCA levels Monday through
Thursday.
For the inner waters S of Point Conception, moderate to high
confidence in the current forecast. Conds are expected to be below
SCA levels for the most part through Thursday night. However, for
the western Santa Barbara Channel, there is a 40%-50% chance
Monday afternoon/evening and Tuesday afternoon/evening.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Sunday for
zones 645-676. (See LAXMWWLOX).
Small Craft Advisory in effect from 3 PM Sunday to 3 AM PDT
Monday for zone 645. (See LAXMWWLOX).
Small Craft Advisory in effect until 3 AM PDT Monday for zone
670. (See LAXMWWLOX).
Small Craft Advisory in effect until 5 AM PDT Tuesday for
zone 673. (See LAXMWWLOX).
&&
$$
PUBLIC...MW/KL
AVIATION...KL
MARINE...Sirard/Ciliberti
SYNOPSIS...MW/CC
weather.gov/losangeles
Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox
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