568
FXUS66 KLOX 221117
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
417 AM PDT Fri Aug 22 2025

.SYNOPSIS...22/408 AM.

Near record heat will continue across the region today as a hot
air mass will remain in place through the weekend. High pressure
aloft over the Four Corners Region will linger through at least
Sunday. Showers and thunderstorms will be possible over the Los
Angeles and Ventura County mountains, and portions of the
Antelope Valley, during the afternoon and evening hours through
Monday. A few showers spilling over into the valleys and foothills
cannot be ruled out over the weekend. A cooling trend is expected
for next week as an upper-level trough approaches the West Coast.

&&

.SHORT TERM (TDY-SUN)...22/408 AM.

The latest water vapor imagery shows an upper-level ridge of high
pressure centered over the Four Corners Region this morning.
Southeast flow aloft in the clockwise flow around the ridge center
is pushing some middle and high level moisture over the region.
Limited low cloud coverage continues across the region and most
areas will see mostly sunny to partly cloudy skies this morning.

A very warm to dangerously hot weather pattern will continue
across the area today. Heat advisories and extreme heat warnings
remain intact at this time and no changes were made, but there
remains a moderate chance of heat advisories or extreme heat
warnings being extended into Sunday. Please continue to stay
hydrated. Schedule any outdoor activities toward the cooler
portions of the day, either the early morning hours or in the
early evening hours. Avoid the midday sun and seek shade or air
conditioning in the afternoon.

Temperatures will be tricky over the coming days as the southeast
flow aloft starts to increase the humidity and increase cloud
cover. In addition, ensemble pressure gradients suggest a slight
uptick in onshore pressure gradients. This could bring a couple of
degrees cooling to the coast, but the increase in the humidity may
make it feel just as warm. While forecast ensembles lean toward
500 mb heights decreasing, which adds some confidence toward
onshore flow increasing, the ensemble members hold on to a near
flat temperature trends for today and Saturday. The forecast
introduces a degree or two of cooling as 950 mb and 850 mb
temperatures trend cooler and the forecast banks on onshore
pressure gradients increasing. That being said, confidence is
moderate at best in that actually materializing due to the history
of upper-level southeast flow patterns in August and September.
There is a 30 percent chance that the temperatures could equal or
hotter than yesterday`s values.

Monsoonal moisture increasing across the region will start to
increase the chances of afternoon and evening showers and
thunderstorms, especially across the mountains and desert.
Ensemble precipitable water values increase to near 1.50 inches,
or about 150 to 175 percent of normal for this time of year. NBM
values were primarily used as a starting point for PoPs in the
forecast, but these values were skewed toward the usual
climatological set up in monsoonal flow patterns. PoPs were
trended drier across the coast and valley areas and trended wetter
over the northern Ventura County mountains, eastern San Gabriel
Mountains, the eastern Antelope Valley over the next several
afternoons and evenings. GFS deterministic solutions and GEFS
ensemble members hint at a spillover of the monsoonal flow
convection across Los Angeles County on Saturday afternoon and
evening, but confidence remains low in its occurrence as high
resolution multi-model ensembles and a vast majority of the EPS
and CMC ensemble members lean dry. Future shifts may need to more
closely examine this wrinkle as we get closer. Looking at the flow
pattern combined with the steering flow, there is a chance that
some storms could be slow-moving on Saturday and Sunday. While it
is not certain exactly where storms will develop and how light
the steering flow may be, brief heavy downpours are possible on
Saturday and Sunday. Residents living near recent burn areas
should monitor the latest forecasts for updates.

A cooling trend should start to get underway on Sunday as 500 mb
heights continues to decline and onshore flow continues to
increase.

.LONG TERM (MON-THU)...22/416 AM.

Increasing onshore flow will allow for the cooling trend to
become more pronounced Monday as an upper-level trough
establishes along the West Coast. Most areas will see the most
pronounced between Monday and Tuesday.

Forecast ensemble members continue to indicate the monsoonal flow
pattern lingering into the next week. NBM values keep slight
chance PoPs in the forecast into late week, but confidence is low
given the upper-level pattern and the declining 500 mb height
means.

&&

.AVIATION...22/0710Z.

At 0644Z at KLAX, the marine layer was 400 ft deep, with an
inversion height of 2700 ft and a maximum temperature of 31 C.

There is a 10-20 percent chance of LIFR/IFR ceilings at any
coastal airport from 08Z-15Z, except for a 30% chance at KOXR and
a 60% chance at KSMX. Otherwise high confidence in VFR conditions.

KLAX...There is a 15 percent chance of OVC002-OVC006 cigs and VSBY
between 2SM-4SM from 11Z-16Z. Otherwise high confidence in VFR
conditions continuing. High confidence in any early morning
easterly winds staying below 06 knots.

KBUR...High confidence in VFR conditions.

&&

.MARINE...22/247 AM.

Moderate confidence in Small Craft Advisories (SCA) being common
each day through at least early next week for the waters beyond 20
miles from shore from the Central Coast the Santa Rosa Island.
Those winds however will likely not last as long as usual with
longer lulls in the morning and early afternoon hours. The waters
from Santa Rosa to San Nicolas will be trending milder, with
choppy seas likely to subside after today.

There is a non-zero chance of isolated thunderstorms over the
waters over the weekend. While a monsoonal surge is likely during
this time, confidence is very low on if, where, and exactly when
any thunderstorms may form.

Fog coverage will limited through the weekend, but random patches
are possible each morning. Any fog that forms will be dense with
visibilities under one mile.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Extreme Heat Warning in effect until 9 PM PDT Saturday 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 341-347-367. (See LAXNPWLOX).
     Heat Advisory remains in effect until 9 PM PDT Saturday for
      zones 356>358. (See LAXNPWLOX).
     Red Flag Warning in effect until 9 PM PDT Saturday for zones
      288-345-351>353-375>382. (See LAXRFWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Saturday for
      zones 670-673. (See LAXMWWLOX).

&&

$$

PUBLIC...Hall
AVIATION...Schoenfeld
MARINE...Phillips/Schoenfeld
SYNOPSIS...Hall

weather.gov/losangeles

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