524
FXUS66 KLOX 220413
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
913 PM PDT Sun Jun 21 2026

.SYNOPSIS...21/825 PM.

A shallower marine layer is expected over the next few days and a
significant warming trend will start Monday, peaking around
Wednesday with well above normal afternoon temperatures. A push of
moisture midweek will bring at least a low chance for rain and
then drier conditions return. Temperatures are expected to cool
heading into the end of the week and the weekend.

&&

.SHORT TERM (SUN-WED)...21/901 PM.

***UPDATE***

Marine layer clouds were fairly widespread this morning for
northern portions of the region, with clouds reaching deep into
the valleys. South of Point Conception, stratus was much more
inconsistent. Clouds cleared fairly quickly over most of the area
though, and high temperatures warmed a touch from yesterday,
especially over interior San Luis Obispo/Santa Barbara Counties
and the Antelope Valley.

Tonight into Monday morning, expecting eddy circulations in the
Santa Barbara Channel and south of Santa Cruz Island to support
marine layer clouds developing and pushing into LA, Ventura, and
southern Santa Barbara Counties. However, clouds have been slow to
form south of Point Conception so clouds may not arrive until the
early morning hours and could struggle to the valleys. Current
forecast looked on track, with developing heat as high pressure
builds over the area. The temperature forecast will be tricky for
the coasts and coastal plains, with the ongoing potential for low
clouds and patchy fog.

***From Previous Discussion***

Overall weather conditions today are similar to yesterday, under
continued zonal flow. High temperatures this afternoon will be
around 1-3 degrees warmer than yesterday for most areas, with the
exception of the valleys of San Luis Obispo County. Midday
temperature readings across the county were up to 5-10 degrees
warmer and than yesterday and should see high temperatures pushing
the low to mid 80s. Elsewhere, coastal areas will top out mostly in
the 70s and beaches will mostly be in the upper 60s to around
70F.

Heading into Monday, H5 heights will start rising, as high
pressure strengthens over the Desert Southwest, and low level
(925mb) temperatures will also steadily climb through Wednesday.
This will lead to a notable warming trend at the surface that
will continue through at least Wednesday and model guidance
continues to show Wednesday being the warmest day of the short
term and the entire week. Afternoon high temperatures away from
the coast are forecast to warm up to 4-10 degrees above normal
beginning Tuesday. Coastal areas will see high temperatures in the
middle 70s to lower 80s, while many inland valleys will reach the
low to middle 90s. These temperatures will lead to widespread
Minor HeatRisk, with areas of Moderate HeatRisk in the warmer
valleys. While this may be considered borderline advisory-level
heat, the risk for heat impacts and the vulnerability to heat is
greater, especially across the LA Area, with an increase in people
not from the area and many larger outdoor events. The Extreme
Heat Watch for Tuesday-Thursday was converted to a Heat Advisory
for portions of LA County.

In addition to the heat, there remains good confidence in a
mid-level moisture push from the south late-Tuesday into
Wednesday, along with potentially a weak shortwave moving through.
Guidance continues to show a 5-15% chance for rain with this push.
Ensembles continue to refine the best area for the rain chances,
with the focus mainly from Ventura and LA Counties eastward.
Model soundings indicate potential for some weak mid-level
instability. So, some elevated convection cannot be ruled out. The
overall odds of measurable rain is low under this regime and much
of the precipitation that falls may evaporate before reaching the
ground due to much drier low levels.

At the surface, moderate to strong onshore flow will prevail with
some weak northerly offshore flow continuing. With gradual
increase in H5 heights, the marine inversion should become a bit
more shallow through the period. So, the expected areal coverage
of stratus should gradually diminish through the short term.
However, given the current chaotic nature of the stratus
development, confidence in the exact behavior of the marine layer
is moderate at best. Other than any stratus issues, skies should
remain mostly clear through Tuesday and then there will be more
mid-level clouds heading into Wednesday. The lowered marine layer
inversion will keep air quality poor in the LA basin area for as
long as the warehouse fire continues. See South Coast AQMD for
updated air quality information.

As for winds, no significant issues are expected. The moderate to
strong onshore pressure gradients will continue to generate gusty
southwesterly winds in the afternoon/evening hours across interior
sections. However, any advisory-level winds will remain localized
across the desert foothills. So, no wind products are expected at
this time.

.LONG TERM (THU-SUN)...21/241 PM.

Through the extended period, models continue to exhibit good
synoptic agreement. At upper levels, ridge slowly weakens
into the second half of the week with broad cyclonic flow
developing on Friday and Saturday. At the surface, moderate to
strong onshore flow will continue with some increase in northerly
offshore flow later in the period.

Heat-wise, late week into the weekend, there will be several
degrees of area-wide cooling each day, especially away from the
coast, as the Desert Southwest high pressure flattens and dips
southward in favor of increased troffing across the Western
CONUS. The increased troffing will also bring about breezier
conditions, potentially advisory-level winds in some areas, across
the region and increase coastal water impacts as well as fire
weather concerns.

&&

.AVIATION...22/0413Z.

At 0400Z at KLAX, the marine layer was around 1200 feet deep.
The top of the inversion was 5100 feet with a temperature of
18 degrees Celsius.

For the 06Z TAF package, high confidence in KPMD and KWJF.

For all other sites, low to moderate confidence in 06Z TAFs.
Timing of flight category changes could be +/- 3 hours of current
forecasts. CIG categories could be either MVFR or IFR.

KLAX...Moderate confidence in 06Z TAF. Timing of flight category
changes could be +/- 3 hours of current forecasts. There is a 50%
chance that CIGs will not drop to IFR levels overnight. No
significant easterly wind component is expected.

KBUR...Moderate confidence in 06Z TAF. There is a 50% chance that
MVFR VSBYs do not develop overnight. There is a 30% chance of IFR
CIGs in the 11Z-17Z time frame.

&&

.MARINE...21/821 PM.

For the Outer Waters, moderate to high confidence in current
forecast. Through Wednesday there is high confidence in winds and
seas remaining below Small Craft Advisory (SCA) levels. Chances
for SCA level winds increase late Thursday afternoon through
Friday morning as a trough tightens pressure gradients over the
area. Probabilities increase to 30-60% from north to south across
PZZ670/673/676.

For the Inner Waters north of Point Sal high confidence in conds
remaining below SCA levels through Thursday, with a chance of
winds increasing to SCA levels Friday night.

For the inner waters south of Point Conception, high confidence
in current forecast. Gusts up to 20 kts are affecting portions of
these waters, in the western SCA Channel and nearshore LA County.
Locally gusty winds 20 to 25 kts will be possible during the
afternoon/evening hours again tomorrow in the western Santa
Barbara channel, south of Point Conception to around the Channel
Islands. Otherwise, conds are expected to remain below SCA levels
through the period, except for a chance of SCA level gusts Friday
evening in the western channel.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory remains in effect from 8 AM Tuesday to 9 PM PDT
      Thursday for zones 88-368-372-373-379-380-548. (See LAXNPWLOX).
PZ...NONE.

&&

$$

PUBLIC...Phillips/SB
AVIATION...RAT
MARINE...Batz/RAT/CMC
SYNOPSIS...SB/CC

weather.gov/losangeles

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

NWS Los Angeles (LOX) Office