039
FXUS66 KLOX 240340
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
840 PM PDT Sat Aug 23 2025

.SYNOPSIS...23/811 PM.

High pressure over the Four Corners Region will persist through
at least Sunday, keeping a very warm air mass over the region.
Monsoonal moisture moving over the area will cause continued
humid conditions, along with possible showers and thunderstorms
over the mountains and desert in the afternoon to evening hours
through Tuesday. A cooling trend is expected for next week as a
weak upper- level trough approaches the West Coast.

&&

.SHORT TERM (SAT-TUE)...23/840 PM.

Monsoon moisture moved into the area today resulting in
some scattered showers and thunderstorms, mostly LA/Ventura
Counties and the coastal waters south of Pt Conception. Moisture
was high based so the rain had to survive a long trip down
through drier air so rain amounts were mostly on the light side.
As a result, the main impacts from today`s thunderstorms included
some dry lightning strikes that started a few small fires, as well
as strong downburst/outflow winds. In fact, one thunderstorm in
the Antelope Valley produced a wind gust of 58 mph at Llano. For
this evening, the convective activity has generally diminished
for the time across our forecast area, but radar is showing a band
of potentially light showers or sprinkles moving into eastern LA
County. Further south, there is more enhanced mid level moisture
streaming northward from San Diego county and northern Baja. There
is still a 5-10 percent chance of monsoon showers/thunderstorms
tonight into Sunday morning as mid level moisture and instability
remain in place.

By Sunday afternoon, the threat of thunderstorms increase to
20-40% across the mountains of LA/Ventura/Santa Barbara counties
as well as the Antelope Valley, with high resolution model data
consensus indicating the highest probability over the northern
Ventura county mountains. Latest model guidance showing increased
lower level moisture on Sunday, with 850 mb dewpoints as high as
13 degrees Celsius over the mountains. In addition, with less mid
level clouds, there will likely be more daytime sunshine to
provide increased instability on Sunday, leading to the threat of
deeper convection. A NAM model sounding over the northern Ventura
county mountains shows these factors coming together with a
slightly better moisture profile than today (especially in the
10,000-20,000 foot range) as well as MUCAPE values in excess of
1600 J/kg. This increased moisture combined with fairly weak
steering flow between 700 and 500 mb will bring the potential for
slow moving thunderstorms on Sunday, capable of localized flash
flooding across the mountains, with the highest threat over the
northern Ventura county mountains. For the Bridge Fire, the
threat of rainfall rates reaching debris flow thresholds is around
10 percent. Outside of the rain cores, there will still be the
threat of isolated dry lightning strikes. In addition, there will
still be the threat of strong/erratic downburst/outflow wind gusts
to 50 mph with thunderstorms.

With all the monsoon moisture around temperatures were all over
the place. In general it was cooler today, though when the clouds
cleared even briefly temperatures soared. Still saw a number of
stations away from the immediate coast climb to between 95 and 105
degrees today. Similar hot temperatures expected on Sunday, with
continued humid conditions, resulting in all Heat Warnings and
Heat Advisories remaining in place, except the Heat Advisories for
the immediate coastal areas, which were allowed to expire this
evening, as slightly cooler temperatures are expected on Sunday.
Other notable item tonight will be patchy dense fog for the
Central Coast and adjacent coastal waters.

Cooling temperatures and increasing onshore flow are expected
Monday and Tuesday as the upper high weakens and shifts back east.
By Tuesday temperatures will be within a few degrees of normal in
most areas. Can`t completely rule out some lingering afternoon
convection Monday and Tuesday across the mountains and AV but
chances will be lower each day as the moisture aloft drops rapidly
next week.

.LONG TERM (WED-SAT)...23/209 PM.

A slow cooling trend will continue through most of the week
as a trough replaces the ridge. Temperatures will be at least 2-5
degrees below normal with increasing night and morning low clouds
and fog that will eventually return to the valleys. Looking a
little farther out models are in good agreement on a rather deep
low pressure system dropping into the Pac NW and far northern
California late next week and remaining there through Labor Day
weekend. This will keep the monsoon well to the east with
relatively cool temperatures across California.

&&

.AVIATION...23/1731Z.

At 1615Z at KLAX, the marine inversion was 600 ft deep. The
top of the inversion was 2100 feet with a temperature of
30 degrees Celsius.

For 18Z TAF package, monsoonal moisture will bring a threat of
showers and thunderstorms from Santa Barbara county southward
through this evening. Lightning strikes and gusty outflow winds
will be the main hazards with brief light to moderate showers
possible.

For coastal sites tonight/Sunday morning, low confidence in
forecast of marine layer stratus/fog. Monsoonal moisture will
likely make the stratus development very chaotic overnight.

KLAX...Overall, moderate confidence in 18Z TAF. High confidence in
VFR conditions through this evening with the possibilty of some
light showers. For tonight, there is a 50% chance that CIG/VSBY
restrictions do not develop. The shower activity could generate
brief periods of easterly winds around 8 knots through 22Z.

KBUR...High confidence in 18Z TAF as VFR conditions are expected
through the period. There is a chance of brief light showers
through this afternoon.

&&

.MARINE...23/814 PM.

For the Outer Waters, moderate to high confidence in current
forecast. High confidence in Small Craft Advisory (SCA) level
winds across all the outer waters. For Sunday through Thursday,
there is a 40-60% chance of SCA level winds across PZZ673/676,
mainly around Point Conception.

For the Inner Waters north of Point Sal, high confidence in
current forecast. Tonight through Thursday night winds and seas
are expected to remain below SCA levels.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. For the western half of the Santa
Barbara Channel, there is a 20-30% chance of SCA level winds
through Thursday during the late afternoon and evening hours.
Otherwise, high confidence in winds and seas remaining below SCA
levels through Thursday for the remainder of the southern Inner
Waters.

Dense fog with visibilities of one nautical mile or less will be
possible this weekend during the night and morning hours,
especially off the Central Coast.

&&

.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 Sunday for
      zones 356>358. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Sunday for
      zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Gomberg/MW
AVIATION...RAT
MARINE...RAT/Ciliberti
SYNOPSIS...Hall/Ciliberti

weather.gov/losangeles

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