844
FXUS66 KLOX 021318
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
618 AM PDT Tue Sep 2 2025

.SYNOPSIS...02/326 AM.

Very warm weather is expected again today. Monsoonal moisture
will last through at least Thursday and will bring a chance of
thunderstorms and showers to the area. The heaviest storms will be
focused over the Antelope Valley and San Gabriel Mountains late
through Wednesday evening. Any storms may produce lightning,
flash flooding, and gusty and locally damaging winds.

&&

.SHORT TERM (TDY-THU)...02/327 AM.

Southern CA is sandwiched between a 593 dam upper high over UT
and a high hgt (582 dam) upper low just to the west of Monterey.
There is moist unstable S to N flow between the two systems.
Currently there is a narrow band of PVA that has triggered a line
of convection across eastern SBA and SLO county and extending
almost due south into the coastal waters. These storms are moving
fairly quickly and do not pose much of flood threat. As the day
progresses the area of greatest instability will shift to the east
over LA county. This is also the area which will contain the
greatest amount of moisture. These two areas will converge late
this morning and will create an environment favorable for TSTM
induced flash flooding and a flood watch is in effect for the mtns
of LA/VTA Counties and the Antelope Valley from 11 AM today all
the way to 11 PM Wed. Most of the Bridge Fire Burn Scar is
included in the watch area. In addition to the flood risk there is
also a potential for TSTM produced wind gusts to 60 mph. In
addition to the risk of TSTMs there is also a heat risk due to
the combination of warmer than normal temperatures and humidity.
Temperatures today could be tricky due to the high clouds. Still
even if temps do cool the increase in humidities will be to keep
the heat danger going.

The upper low will continue to bring pockets of vorticity to the
area tonight and the threat of TSTMs will continue. Tonight,
however, the threat will be confined to the LA/VTA mtns and AV.
Low clouds will likely form again across many of the coastal
sections, but they ma be disrupted in places from the clouds
streaming overhead.

The TSTM threat will continue Wednesday. The threat will be
confined to the LA/VTA county mtns, the AV and the eastern portion
of the San Gabriel Vly. The steering flow is weaker than it is
today and this will increase the flooding risk. Max temps will
cool 2 or 3 degrees - this may not be enough to end the heat risk
and the heat advisories may need an extension into the early
evening.

The upper high pushes to the east on Thursday and troffing will
move into the state. This will increase the odd of a more robust
coastal marine cloud layer. There will be just enough moisture for
a slight chc of afternoon TSTMs over the LA/VTA mtns. The lower
hgts and stronger onshore flow will bring 3 to 6 degrees of
cooling to the area and this will be enough to eliminate the need
for heat advisories.

.LONG TERM (FRI-MON)...02/327 AM.

Long wave troffing sets up over the west coast on Friday and
continues into Saturday. Onshore flow increases as well. This will
lead to an increase in the morning marine layer cloud layer and a
couple degrees of cooling each day.

On Sunday and continuing into Monday a ridge will nudge up from
the north. An increase in onshore flow, however, will negate any
possible warming from the rising hgts.

&&

.AVIATION...02/1317Z.

At 1233Z at KLAX, the marine layer was 1000 ft deep. The top of
the inversion was near 3200 feet with a temperature of 27 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 through 06Z Wed 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 through 06Z Wed. High confidence that any east
wind component will remain below 7 kt.

KBUR...Moderate confidence in TAF. There is a 25 percent chance
of showers and thunderstorms through 06Z Wed.

&&

.MARINE...02/326 AM.

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

Today through Thursday night, winds will increase across the
central and southern outer waters, with the highest chances of
Small Craft Advisory (SCA) level winds focused around Point
Conception and southward to San Nicolas Island, thus an advisory
has been issued. A relative lull in winds will be likely each
morning. There is a 40% chance of SCA level winds across all the
outer waters during the afternoon and evening hours Friday through
the weekend.

Moderate confidence in forecast for the nearshore waters along
the Central Coast. There is a 20-30% chance of SCA winds each
afternoon and evening through the weekend.

Winds will increase in speed and coverage across the nearshore
waters South of Point Conception, with a 40% chance of SCA conds
during the afternoon and evening hours today through Thursday
(decreasing to 30% for the same hours Friday through the weekend)
across western portions of the waters, as well as near Point Dume
and into the San Pedro Channel.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory remains in effect until 6 PM PDT this evening
      for zones 38-88-344-345-352-353-355>358-368>379-548. (See LAXNPWLOX).
     Flood Watch in effect from 11 AM PDT this morning through
      Wednesday evening for zones 379>383. (See LAXFFALOX).
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3
      AM PDT Thursday for zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Rorke
AVIATION...Rorke/Lund
MARINE...Lund
SYNOPSIS...Schoenfeld/Ciliberti

weather.gov/losangeles

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