341
FXUS66 KLOX 231201
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
501 AM PDT Sat Aug 23 2025

.SYNOPSIS...23/307 AM.

High pressure aloft over the Four Corners Region will remain in
place through at least Sunday and keep a hot air mass over the
region. Monsoonal moisture will continue to spill into the region
today, adding more humid conditions to go along with the heat.
Showers are possible for areas south of Point Conception today,
becoming more confined to mountains and desert as the day
progresses and into Sunday and Monday. A cooling trend is expected
for next week as a weak upper-level trough approaches the West
Coast.

&&

.SHORT TERM (TDY-MON)...23/314 AM.

The latest water imagery shows an upper-level ridge of high
pressure centered over the Four Corners Region this morning.
Southeast flow aloft over the region is continuing to push
moisture from the Southwest Desert Monsoon into the area. The
latest radar and satellite imagery indicate an area of developing
convection off the northern Baja California coast. A few lightning
strikes are already occurring with this area of convection. The
latest model solutions show this area of convection rotating into
Ventura and Los Angeles Counties later today. Almost all of GEFS
solutions advertise measurable rainfall occurring at Los Angeles
and Ventura County airports today. Looking at higher resolution
models, the latest NCEP HIRES-FV3 and HRRR solutions indicate some
convective showers streaming into the southern California bight
and into Los Angeles and Ventura Counties, but as with convective
processes in numerical modeling, it may not encapsulate the
coverage and exact locations properly. PoPs have been nudged
higher for these aforementioned areas today and mentions of
showers are in the forecast along with some cloud cover. It
should be stated that this is a low confidence forecast as the
source region of the moisture is in a data sparse region.

With the southeast flow aloft bringing in some moisture,
temperatures will be tricky today. If widespread showers and
partly to mostly skies develop later this morning, today could end
up more cloudy and cooler day. This could tick down the heat risk
values below what is in the forecast. However, if there are any
breaks in the activity and the skies turn mostly sunny, the air
mass will heat up rapidly with added humidity. Heat index values
could soar in a pattern like this with any sunshine. NBM and the
latest forecast guidance leans toward cooling being the end
result today, but low confidence exists. In addition, the added
humidity could end up making the day seem just as warm to the
human body. Given the uncertainty, the heat advisory and extreme
heat warning headlines remain intact and no changes were made.
This will need to be watched closely by future shifts for
potential updates.

Along the Central Coast and into the southern California bight,
there is a sign that points to cooling temperatures today as low
clouds and fog are becoming well-entrenched, pushing low clouds
and dense fog into Central Coast. An eddy circulation can be seen
forming near Catalina Island this morning. Low clouds and fog
could approach the Southland beaches later this morning, but
moderate confidence exists at this time. The reason for lower
confidence would be monsoonal moisture streaming over the region.
Middle and high level cloudiness and any convection could mess
with the marine layer depth and play tricks on the marine inversion.
Pockets with the marine layer mixing out seem plausible given the
pattern. Low clouds and fog will likely be patchy at best south
of Point Conception, and the best coverage would be along the
Central Coast of California. Low confidence should be exercised
in the low clouds forecast over the next several days as similar
issues could occur.

A very warm to hot air mass looks to remain in place through at
least Sunday, or possibly into Monday, as the upper-level ridge is
slow to breakdown and push away to the east. A shortwave trailing
along the south side of an upper-level trough over the Gulf of
Alaska is slower to split off from the parent trough and move into
the West Coast region. A hint of a southwesterly flow component
develops on Monday, which could bring better cooling, but the
latest model solutions all hold off until Tuesday for the trough
to firmly establish itself and southwesterly flow aloft to become
entrenched.

.LONG TERM (TUE-FRI)...23/316 AM.

The extended forecast is a little murkier as the cluster analysis
is weakening the trough`s influence into middle to later portion
of next week. Ensemble solutions still show some cooling in the
forecast, but the amount of cooling is in question. Overall, the
pattern favors southwest flow aloft but much weaker than
previously expected. Most areas should cool to near normal or
slightly below normal by Wednesday. The latest ensemble members
and cluster analysis is starting to favor a return to a warmer
weather pattern for late next week. Low clouds and fog should
return to the coastal areas and an onshore flow should remain in
place through Thursday, but a warming trend could shape up
thereafter with onshore flow weakening.

There remains a hint of monsoonal moisture in the forecast.
Slight chance PoPs are kept in for Wednesday and Thursday, but
southwest flow aloft advertised by the cluster analysis should put
a lid on the atmosphere. Low confidence should be exercised with PoPs
into later portion of the forecast.

&&

.AVIATION...23/1200Z.

At 0651Z at KLAX, the marine inversion was 900 ft deep, with an
inversion top around 2400 feet with a max temperature of 30 C.

From 18Z Sat to 06Z Sun, thunderstorms will be possible for KPMD
and KWJF, as well as across the interior mountains. The greatest
chances of storms will be from 20Z Sat to 00Z Sun, when there is
around a 30% chance for the high elevation mountains and deserts
(including KPMD and KWJF). Lighting, VRB18G30KT wind, and
turbulence will be possible with storms. Showers will be possible
for much of LA and Ventura Counties from 14Z Sat to 00Z Sun.

At all coastal sites, there is at least a 15-25% chance of LIFR
conditions from 13Z-16Z Sat, though any cigs that form may scatter
and reform. Generally low confidence in the timing of the
development of flight cat restrictions.

KLAX...Moderate confidence in TAF. There is a 20% chance of
several hours of VSBY as low as 1SM from 13-16Z Sat. There is a
5-10% chance of showers/thunderstorms from 14Z Sat to 00Z Sun. No
significant easterly wind component is expected.

KBUR...High confidence in TAF. There is a 10-20% chance of
showers/thunderstorms from 14Z Sat to 00Z Sun.

&&

.MARINE...23/307 AM.

There is a slight chance for isolated to scattered showers and
thunderstorms for the waters south of the Channel Islands today.
Showers and thunderstorms can create localized dangerous ocean
conditions with choppy seas, gusty erratic winds, and the
potential for cloud to sea lightning. Boaters should closely
monitor weather conditions and avoid traveling near showers and
thunderstorms.

Fog will be widespread this morning for the outer waters and
inner waters north of Point Conception, and patchy everywhere
else. Any fog that forms will be dense with visibilities under one
mile, and patchy fog will be possible each night and morning
through Wednesday.

For the Outer Waters, moderate to high confidence in current
forecast. Through Wednesday during the late afternoons and
evenings, there is a 40-60% chance of SCA level winds, with the
best chances around Point Conception.

For a majority of the Inner Waters, high confidence in winds and
seas remaining below SCA levels through Wednesday. The only
exception will be the western half of the Santa Barbara Channel,
where there will be a 20-30% chance of SCA level winds Sunday
through Wednesday, mainly in the late afternoon and evening hours.
Gusts of around 20 kt will be possible this afternoon and evening
around Point Dume and across the San Pedro Channel.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Extreme Heat Warning in effect until 9 PM PDT Sunday for
      zones 38-88-342>345-348-351>353-368>383-548. (See LAXNPWLOX).
     Heat Advisory remains in effect until 9 PM PDT this evening
      for zones 87-349-350-354-355-362-366-367. (See LAXNPWLOX).
     Dense Fog Advisory in effect until 9 AM PDT this morning for
      zones 340-341-346-347. (See LAXNPWLOX).
     Heat Advisory remains in effect until 9 PM PDT Sunday for
      zones 356>358. (See LAXNPWLOX).
     Red Flag Warning in effect until 9 PM PDT this evening for
      zones 288-345-351>353-375>382. (See LAXRFWLOX).
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3
      AM PDT Sunday for zones 670-673. (See LAXMWWLOX).

&&

$$

PUBLIC...Hall
AVIATION...Schoenfeld
MARINE...RAT/Schoenfeld
SYNOPSIS...Hall

weather.gov/losangeles

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