561
FXUS66 KLOX 020614
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1114 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...02/0609Z.

At 0505Z at KLAX, the marine layer was 900 ft deep. The top of
the inversion was near 1800 feet with a temperature of 28 C.

Low confidence in low cloud forecast as low clouds could form
dissipate and reform as the high level mositure passes overhead.
There is a 25 percent chc of IFR cigs at KPRB, KBUR and KVNY
12Z-15Z.

There is a 25 percent chc of a less than 1 hour in duration shower
or TSTM at all sites from 12Z-06Z except for a 30 to 40 percent
chc for KPMD and KWJF.

KLAX...Low confidence in TAF. Low clouds may move into and and out
of the area through 16Z. There is a 20 percent chc of a brief
shower or TSTM 12Z-06Z. High confidence that any east wind
component will remain below 7 kt.

KBUR...Moderate confidence in TAF. There is a 20 percent chc of
OVC004 conds 12Z-15Z. There is a 25 percent chance of showers and
thunderstorms 12Z-06Z.

&&

.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).
     Flood Watch in effect from 11 AM PDT Tuesday through
      Wednesday evening for zones 379>383. (See LAXFFALOX).
PZ...NONE.

&&

$$

PUBLIC...Phillips/Schoenfeld
AVIATION...Rorke
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