699
FXUS66 KLOX 241701
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1001 AM PDT Sun Aug 24 2025

.SYNOPSIS...24/927 AM.

High pressure over the Four Corners Region will persist through
at least today, 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 the rest of the week as a
weak upper-level trough approaches the West Coast.

&&

.SHORT TERM (TDY-TUE)...24/944 AM.

***UPDATE***

Looking like a much less active day today as there is less
monsoon moisture around and convective parameters are quite a bit
weaker than yesterday. Still should see some isolated showers and
storms by afternoon over the LA/Ventura mountains but overall
weaker intensity and not expecting anything over the coastal and
valley areas.

It will be another hot day today, getting a faster start since
there is little to no cloud cover this morning. Expecting temps
similar or even a little warmer as onshore gradients are weaker to
the north and east and there is less moisture in the air. Most of
the coastal valleys will easily top 100 today as will the deserts,
and the intermediate areas between the coast and valleys will be
in the 90s. Heat advisories and Extreme heat warnings continue in
most of the same areas as Saturday and will have to give some
consideration of adding at least heat advisories to some areas
Monday.

***From Previous Discussion***

A 593 dam upper high continues to sit atop of the 4 corners
region. At the sfc there will be weak onshore flow both to the
east and west. Temperatures will be similar to ydy save for the
Antelope Vly where less cloud cover is forecast and temps are
forecast to rise by 3 to 6 degrees. The monsoon has pumped up
humidities across the area. In addition to making the daytime
temperatures feel worse the added moisture is also hindering the
overnight cooling. The combination of warm overnight lows,
humidity and above normal temperatures will create one more day of
dangerous heat conditions and heat warnings and advisories are in
effect through this evening.

The monsoon flow will also continue the threat of showers and
TSTMs. There is a little more moisture at the lower levels this
afternoon, so any TSTM that develops could produce more rainfall
than those ydy. The steering flow is also weak so there is risk
of flash flooding this afternoon. Some of the TSTMs will be high
based and will continue the threat of dry lightning. In addition,
there will still be the threat of strong/erratic wind gusts up to
50 mph under and near to any TSTM that develops.

The high pretty much collapses on Monday and a weak upper low sets
up over the northern 2/3rds of the state. Some coastal low clouds
will develop as well. Hgts will fall to 588 dam. Max temps will
drop 3 to 6 degrees. This cooling will be enough to end the heat
issues. Enough residual moisture will remain over the mtns to
warrant a slight chc of TSTM for the LA/VTA mtns and the AV.

More marine layer and better onshore flow along with the upper
low`s influence will knock another 2 to 3 degrees off of the
temps on Tuesday. This cooling will bring max temps down to near
normal. Mdls still show just enough moisture for a slight chc of a
shower of TSTM in the afternoon over the LA/VTA mtns and the AV.

.LONG TERM (WED-SAT)...24/342 AM.

Mdls are in decent agreement that an upper low will approach the
PACNW and then sweep into British Columbia. This will bring dry SW
flow into Srn CA which will eliminate the monsoon threat. Onshore
flow increases to moderate levels and along with troffing aloft
will work to bring night through morning low clouds to most of the
coasts and some of the lower vlys. Most max temps will slowly
cool through Friday when vly highs will only be in the mid 80s to
lower 90s or 4 or 5 degrees under normal. A few degrees of warming
is forecast for Saturday although given the pattern this may be
optimistic.

Looking further out to the rest of the Holiday weekend there does
not look like any meaningful weather with a warming likely both
days Sun and Mon.

&&

.AVIATION...24/1700Z.

At 1600Z at KLAX, the marine layer was 800 ft deep. The top of
the inversion was 3600 feet with a temperature of 27 C.

For 18Z TAF package, high confidence in valley and desert TAFs
with VFR conditions expected through the period.

For coastal sites, moderate confidence in 18Z TAFs. Timing of
flight category changes for KSBP and KSMX could be +/- 2 hours of
current forecast. South of Point Conception, there is a 30% chance
of CIG/VSBY restrictions for KSBA, KOXR and KCMA. For KSMO, KLAX
and KLGB, there is a 40% chance that CIG/VSBY restrictions do not
develop tonight.

KLAX...Moderate confidence in 18Z TAF. There is a 40% chance that
CIG/VSBY restrictions do not develop tonight. If the restrictions
do develop, timing of flight category changes could be +/- 3 hours
of current forecasts. No significant easterly wind component is
expected.

KBUR...High confidence in 18Z TAF.

&&

.MARINE...24/715 AM.

For the Outer Waters, high confidence in Small Craft Advisory
(SCA) level winds through at least late tonight. For Monday
through Thursday, there is a 40-60% chance of SCA level winds,
mainly around Point Conception during the afternoons and evenings.

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 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 this evening
      for zones 38-88-342>345-348-351>353-368>383-548. (See LAXNPWLOX).
     Heat Advisory remains in effect until 9 PM PDT this evening
      for zones 356>358. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Monday for
      zones 670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 3
      AM PDT Monday for zone 676. (See LAXMWWLOX).

&&

$$

PUBLIC...MW/Rorke
AVIATION...RAT
MARINE...Ciliberti/Schoenfeld/RAT
SYNOPSIS...MW/Hall/Ciliberti

weather.gov/losangeles

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