325
FXUS66 KLOX 020349
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
849 PM PDT Mon Sep 1 2025

.SYNOPSIS...01/630 PM.

Very warm weather is expected again tomorrow. Monsoonal moisture
will arrive tonight and last through at least Thursday. There is a
chance of thunderstorms and showers focused over the Antelope
Valley and San Gabriel Mountains late Tuesday morning through
Wednesday evening. Any storms may produce lightning, flash
flooding, and gusty and locally damaging winds.

&&

.SHORT TERM (MON-THU)...01/848 PM.

***UPDATE***

Temperatures were hot again today as expected with 100s common for
valleys and the interior, and 80s to 90s closer to the coasts.
Tomorrow`s temperature forecast will be quite tricky, as clouds
are already pouring into the area tonight, along with a chance of
showers and thunderstorms. An upper level low just to the
northwest appears to help pull more moisture in from the south
along with bringing instability and vorticity advection that
should support shower and thunderstorm chances. Guidance has been
struggling with the location, timing, and coverage of
precipitation over the area, but the San Gabriel Mountains and
Antelope Valley still look like they will see more widespread
showers late Tuesday night, early Wednesday. Another timeframe to
watch will be Wednesday afternoon, as some guidance initiates wet
thunderstorms over the San Gabriel mountains that could bring
localized flooding.

***From Previous Discussion***

Another very warm to hot day is expected today, although the
impact of stronger onshore flow and upper level clouds late in the
day may dampen daytime maximum temperatures. Heat Advisories are
in effect for much of the areas through Tuesday, with a small
chance of some headlines being extended into Wednesday and/or
expanded to include the coasts of LA/Ventura Counties.

Mositure and instability from the convective activity currently
over Baja California will intersect the region late tonight into
Tuesday. Chances of thunderstorms will begin tonight with a 10-20
percent chance of storms for most areas south of Point Conception
(including the coastal waters, coasts and valleys). Tonight
through tomorrow morning the the main threat with storms will be
lighting fire starts and gusty and erratic outflow winds (gusts
35-50 mph), as moisture will be elevated. Starting tomorrow
afternoon, widespread showers will become increasingly likely,
with thunderstorm chances focused over the mountains of LA and
Ventura Counties and the Antelope Valley. A Flood Watch has been
issued from 11 AM Tue to 11 PM Wed, for much of the San Gabriel
Mountains and the Antelope Valley (including the Bridge Fire Burn
Scar), due to a long duration of risk of flash flooding from
thunderstorms with a risk for damaging winds gusts up to 60 mph.
There is a chance for high clouds to inhibit thunderstorm
development somewhat Tuesday afternoon, however vorticity will
maintain chances for showers/thunderstorms during the less typical
overnight and Wednesday morning hours, thus the reasoning for
long duration Flood Watch. Moderate steering flow out of the west
will provide some storm motion on Tuesday, but by Wednesday
steering flow expected to weaken with slower moving storms
favored.

Overall confidence in high temperatures will be low through the
week due to many variables at play, including elevated 500 mb
heights, light offshore flow at times, increasing cloud coverage,
and higher humidity. Thunderstorm chances are likely to continue
through Thursday, and marine layer clouds will likely be minimal
for most coasts and valleys.

.LONG TERM (FRI-MON)...01/208 PM.

A pattern shift is likely starting Friday, as a weak trough digs
into the region, cooling temperatures and bringing dry
southwesterly flow aloft. This will lead to a drop off in
monsoonal mositure, although a chance for thunderstorms may
linger into Friday. Saturday into early next week, lower 500 mb
heights combined with stronger onshore flow will result in
temperatures near or below normal across the area.

&&

.AVIATION...02/0129Z.

At 0100Z at KLAX, the marine layer was 500 ft deep. The top of the
inversion was near 1600 feet with a temperature of 30 C.

Low to moderate confidence in the 00Z TAFs at the coastal airfields.
Most coastal airfields should have low clouds and IFR/LIFR conds
tonight into Tue morning, but confidence in timing may be off +/-
an hour or two. KSBA is not forecast to have low clouds but there
is a 30% chance of IFR conds developing overnight There is also a
30% chance of no low clouds for KLAX, KSMO and KLGB due to mid
and high clouds moving in tonight possibly disrupting the low
cloud development.

Moderate confidence for the 00Z TAFs over the valleys and
deserts. There is a 20-30 percent chance of showers and
thunderstorms for KBUR and KVNY, mainly after 06Z. For the desert
sites, the chance of showers and thunderstorms will increase
overnight into Tuesday, with a 40-50 percent chance by 12Z Tuesday
through the afternoon.

KLAX...Low to moderate confidence in the 00Z TAF. The airfield
should have low clouds and IFR conds tonight into Tue morning, but
the cloud cover may be broken or intermittent, with a 30 percent
chance of no low clouds. High confidence that any east wind
component will remain below 7 kt.

KBUR...Moderate confidence in the 00Z TAF, with reduced confidence
due to the 20-30 percent chance of showers and thunderstorms at
the site, 06Z tonight through 00Z Wednesday.

&&

.MARINE...01/752 PM.

There is a slight chance of thunderstorms over the Inner Waters
south of Point Conception late tonight through Tuesday morning,
especially the waters adjacent to the Los Angeles and Orange
County coasts. Any thunderstorm may produce frequent lightning,
rain, and gusty, erratic winds.

Winds are expected to remain below SCA levels through Tonight.
For Tuesday through Thursday night, winds will increase across the
central and southern outer waters, with the highest chances of
SCA winds focused around Point Conception and southward to San
Nicolas Island. A relative lull in winds will be likely each
morning. Conds should then be just below SCA levels Friday
through Saturday night.

Moderate confidence in forecast for the nearshore waters along
the Central Coast. Winds and seas will remain below SCA levels
through Saturday night, but winds will increase some Tuesday and
Friday afternoon and evening with a 20-30% chance of SCA conds.

Light winds and small seas are expected for the nearshore waters
south of Point Conception through tonight. Winds will increase in
speed and coverage Tuesday through Thursday, with a 40% chance of
SCA conds Tuesday and Wednesday during the afternoon and evening
hours across western portions of the waters, as well as near
Point Dume and into the San Pedro Channel. Conds should then
remain below SCA levels Friday through Saturday night.

&&

.BEACHES...01/110 PM.

A long period southerly swell will continue through this evening.
Hazardous rip currents are likely for Los Angeles and Ventura
County beaches, as well as Central Coast beaches. Elevated surf
(up to 6 feet) will be possible at south and southwest facing
beaches during the period. If you are at the beach this Labor Day
Weekend, swim near a lifeguard tower and stay aware of ocean
conditions.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory remains in effect until 6 PM PDT Tuesday for
      zones 38-88-344-345-352-353-355>358-368>379-548. (See LAXNPWLOX).
     Beach Hazards Statement in effect until 11 PM PDT this
      evening for zones 340-346-354-362-366. (See LAXCFWLOX).
     Flood Watch in effect from Tuesday morning through Wednesday
      evening for zones 379>383. (See LAXFFALOX).
PZ...NONE.

&&

$$

PUBLIC...Phillips/Schoenfeld
AVIATION...Ciliberti
MARINE...Sirard/Ciliberti
BEACHES...Sirard
SYNOPSIS...Schoenfeld/Ciliberti

weather.gov/losangeles

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