344
FXUS66 KLOX 031755
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1055 AM PDT Wed Sep 3 2025

.SYNOPSIS...03/921 AM.

Very warm conditions will continue today, then temperatures will
slowly lower through Friday, including the abnormally warm
overnight temperatures. Relief is on the way. Monsoonal moisture
will remain over the region through Thursday, bringing risks of
strong winds, brief heavy downpours, lightning, and fire starts
over Los Angeles County.

&&

.SHORT TERM (TDY-FRI)...03/1055 AM.

***UPDATE***

Quiet start to the day on the rain/thunderstorm front, with all
the activity far to our east. That seems to be the trend in all
the computer model projections as well, with very few showing any
convection at all this afternoon. This is a big change compared to
how those projections looks for the past couple of days. The basic
convective parameters still look favorable for thunderstorms over
the Mountains and deserts from Santa Barbara to Los Angeles
Counties (Lifted Index -2, MUCAPE 2,000 J/Kg, K-Index 40, 850
millibar dewpoint 12 degrees C). The lack of any high resolution
model support however brings a lot of doubt however about major
convection. The risk for heavy rain and flooding Will look more
at the current Flood Watch on if we need to end that early.

Definitely a warm day again today, with most coastal and valley
areas over all four counties trending up from yesterday. This
includes Ventura and Los Angeles Counties where the Heat
Advisories remain in place today. While tomorrow will be warm
again, both the daytime highs and overnight lows should be down a
few degrees over today as the high to the east shifts some and
onshore flow strengthens. As a result, there are no plans of
extending the Heat Advisories.

***From Previous Discussion***

Quite weather covers Srn CA at the moment. Skies are clear and
temps are above normal and its a little on the humid side. There
is hardly any upper flow over the area as the upper high that was
over UT ydy has weakened considerably. There is little to no
marine layer clouds this morning and also very little in the way
of mid and high level debris clouds. The extra sunshine and lack
of marine layer will bring 1 to 3 degrees of warming to most
areas. This warming along with the continued higher than normal
humidity will bring advisory level heat to most areas away from
the beaches. There is still enough moisture left in the atmosphere
(1.25" PWATs) to bring a chance of afternoon TSTMs over the VTA/LA
mtns as well as the Antelope Vly. Any TSTM that forms will move
very slowly due to the very weak steering flow and this will
enhance the potential for flash flooding. A Flash Flood Watch is
in effect for the VTA/LA mtns as well as the Antelope Vly

Things begin to settle down on Thursday. Weak flow will remain
aloft as the area will sit under the eastern edge of an E Pac
high. Hgts will fall to 588 dam about 3 dam lower than today.
There will also be a significant increase in onshore flow both to
the east and north. despite the increase in onshore flow, there
will likely not be much of any marine layer stratus in the morning
as there is just no source of lift. Most max temps will cool 3 to
5 degrees and while max temps will end up several degrees over
normal it will not be advisory level heat. It will also be less
humid making things feel even better. Just enough moisture at the
higher levels to bring a slight (20 percent) chc of TSTMs to the
mtns in the afternoon.

Hgt fall further to 585 dam on Fri. Onshore flow will continue to
increase. Low cloud will likely form across many of the coasts.
The flow will be from the west and will be dry eliminating the
TSTM threat. Most areas will cool an additional 2 to 4 degrees.
Max temps away from the beaches in the cstl areas will be in the
upper 70s to mid 80s, while the vlys will mostly end up in the
upper 80s to mid 90s.

.LONG TERM (SAT-TUE)...03/307 AM.

Benign weather on tap for the four day xtnd period. Broad troffing
will move into the western states over the weekend and then the
trof will sharpen early next week. There will be onshore flow
through the period with a moderate onshore push to the east in the
afternoons. The marine layer clouds will likely cover most of the
coasts and may xtnd into the lower vlys. But other than the
morning stratus skies should be mostly clear.

Max temps will fall another 1 to 3 degrees over most of the area
(The Central Coast will warm some as there will be weaker onshore
flow there). This cooling will bring most max temps down to 2 to 4
degrees blo normal. After Saturday`s cooling there will be little
day to day change in temps.

&&

.AVIATION...03/1109Z.

At 1720Z at KLAX, the marine layer was 700 ft deep. The top of the
inversion was at 2200 ft with a temperature of 27 C.

*A national METAR outage continues across the region, and there
will be limited or no amendments until observations are restored*

Overall, moderate to high confidence for 18Z TAF Package. LIFR to
IFR conditions likely at KSBP & KSMX after 03Z Thu. There is a 30%
chance of LIFR to IFR conds at KCMA & KOXR from 10Z to 16Z Thursday.
Otherwise, generally expect VFR conditions through the period.

KLAX...Moderate confidence in 18Z TAF. There is a 20% chance of
LIFR to IFR conditions through 16Z Thursday. No significant east
wind component expected.

KBUR...High confidence in 18Z TAF.

&&

.MARINE...03/744 AM.

Moderate confidence in the current forecast. Higher confidence in
the forecast for seas relative to winds.

For the waters southwest through northwest of the Channel Islands
and the nearshore waters along the Central Coast, there is a
high-to-likely chance of Small Craft Advisory (SCA) northwest
winds through at least Thursday evening. The highest chance will
be for the waters from around Point Conception south to San
Nicolas Island with elevated chance offshore of the Monterey-San
Luis Obispo County border. There is a moderate-to-high chance of
SCA level winds each afternoon and evening over the weekend,
increasing to a high chance for early next week.

Inside the southern California bight, there is a moderate-to-high
chance of SCA level winds each afternoon and evening through
Thursday evening, highest across the western/southern portion of
the Santa Barbara Channel and into the Anacapa Passage, near Point
Dume, and into the San Pedro Channel. Winds and seas should drop
below SCA levels over the weekend, but start to increase again
early next week.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory remains in effect until 6 PM PDT this evening
      for zones 88-355>358-368>375-548. (See LAXNPWLOX).
     Flood Watch in effect through this evening for zones 379>383. (See LAXFFALOX).
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 9
      PM PDT this evening for zones 645-650-670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Thursday for
      zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Rorke/Kittell
AVIATION...Black
MARINE...Hall/Black
SYNOPSIS...RK

weather.gov/losangeles

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

NWS Flagstaff Office