Duarte Weather

183
FXUS66 KLOX 170351
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
851 PM PDT Sun Aug 16 2026

.SYNOPSIS...16/850 PM.

Night through morning marine layer clouds will be confined to the
near coastal areas through much of this week. Warmer and drier
conditions are expected away from the immediate coast, with peak
heat likely being Tuesday through Thursday when moderate heat
risk is expected in warmest locations.

&&

.SHORT TERM (TDY-WED)...16/843 PM.

***UPDATE***

Highs today came in about 1-6 degrees below normal today for this
time of year, with 90s to 100 for the interior, mid 80s to 90s for
the valleys, and cooler 60s and 70s near the coasts. Temperatures
will be trending warmer over the next few days as high pressure
strengthens, with heat advisories beginning Tuesday. Gusty
sundowner winds will develop each evening through the week, with
the best chance to reach advisory levels Monday evening. High
temperatures were adjusted slightly to account for colder highs
along the Central Coast. Monsoonal moisture could bring
showers/thunderstorms as early as Thursday afternoon, but better
chances are possible Friday afternoon. Otherwise the forecast
looks on track.

***From Previous Discussion***

Upper level ridge of high pressure beginning to expand westward
over southern California today with rising heights. This in
combination with slight weakening of onshore pressure gradients
has started a warming and drying trend, with many interior areas
climbing well into the 90s today. As heights continue to build the
next couple of days and onshore pressure gradients weaken
slightly, looking for marine layer cloud coverage to become less
extensive, mainly confined to the coast.

The warming trend remains on track through much of this coming
week, with heat likely peaking Tuesday-Thursday. 500 mb heights
will continue to increase gradually through Tuesday before
plateauing as the large area of high pressure across the Southern
United States marches westward. This combined with weakening
onshore flow will swing temperatures right back up to around 5-10
degrees above seasonal normals in the Tuesday-Thursday time frame.
Overnight temperatures will increase each day as well with most
areas south of Point Conception seeing lows drop down to only the
mid 60s to low 70s, with many foothill and mountain locations
seeing minimum temperatures in the mid 70s to lower 80s by mid
week. For the peak of the heat Tuesday through Thursday, warmest
valley, lower mountain, and desert locations are expected to range
between 95 and 105 degrees.

With afternoon forecast, have included heat advisories for Tuesday
through Thursday for areas that have highest confidence for
moderate heat risk including the warmest mountain and valley
locations (including San Fernando, San Gabriel, and Santa Clarita
Valleys). There is a 30-50 percent chance of heat advisories
being expanded to include more areas, with potential
considerations including LA interior coast (downtown LA), the
Ventura county valleys, and Santa Monica mountains. There is
increasing confidence that Downtown LA will top 90 degrees
sometime between Tuesday and Thursday. The warmer overnight lows
will also add to the heat discomfort, especially in LA county. The
shallow marine layer will help likely help keep temperatures at
immediate coastal areas moderate during the warm up.

Gusty northwest to north winds will begin increasing tonight
across southwest Santa Barbara County as well as interior mountain
areas, especially the I-5 corridor near the Grapevine. While
winds are expected to generally remain sub-advisory levels the
next few days, there is a moderate chance for winds to reach
advisory criteria in portions of southwest Santa Barbara County
Monday night. The focus of the sundowner winds each evening will
be from Gaviota to San Marcos Pass, with the Monday evening
event likely generating gusts up to 45 mph near Gaviota/Refugio.
The peak Santa Barbara-Santa Maria gradient on Monday evening
is expected to be -4 mb. The sundowner winds this week will bring
some warning into the 80s to lower 90s in windy canyons/foothills
by Monday evening, then slightly warmer the following few
evenings as the air mass warms up. These increasing winds across
southwestern SB County may also delay or completely hinder the
formation of marine layer clouds across the south coast of the
county as well as Ventura County. If the marine layer does in fact
not develop over these areas, temperatures could be warmer than
advertised.

.LONG TERM (THU-SUN)...16/245 PM.

Upper level ridging will continue to bring warm and dry
conditions to Southwest California through the work work. Onshore
flow will also be its weakest Wednesday through at least Friday.
The resulting widespread Moderate Heat Risk will also lead to a
moderate chance for heat headlines away from the coast through at
least Thursday, but increasing model agreement for Friday brings
it into play as well. The marine layer will likely be confined
just to the immediate coastal areas, and there is a small chance
that dense fog will occur as the marine layer depth will be quite
shallow.

Friday through next weekend, there maintains some uncertainty in
the evolution of the upper level pattern. Cluster analysis still
shows fairly similar chances of weak troughing setting up along
the coast vs the ridge maintaining its position out west. Suffice
to say confidence from Saturday on is fairly low. While the former
solution favor a cooling trend, the latter favor continued hot
weather and even a small chance for monsoonal convection. The
current heat advisories that are in effect Tuesday-Thursday
may need to be extended into Friday or even next weekend if
the warmer solution verifies.

While winds aren`t expected to be of any widespread significance,
the increasing northerly pressure gradient will likely allow for
gusty north to northwest winds each night across the interior
mountains (especially the Grapevine), deserts, and southwest Santa
Barbara County. While widespread advisory level winds aren`t
likely in the extended period either, there is a chance for
portions of southwest SB County to reach advisory levels. As in
the short term, increasing northerly winds across southwestern SB
County could disrupt the formation of marine layer clouds across
the south coast of the county as well as Ventura County. Again,
this could result in warmer temps along the coasts.

&&

.AVIATION...17/0205Z.

At 0046Z at KLAX, the marine layer was at 900 feet deep. The top
of the inversion was near 2300 feet with a temperature of 27 C.

High confidence in VFR TAFs for KPMD & KWJF. Brief cigs are
possible at KSBA, KBUR, and KVNY.

Low to moderate confidence in remaining TAFs. Arrival times of
IFR/MVFR conds tonight may be off +/- 2-3 hours. Patchy marine
layer may also cause conds to bounce between VFR and MVFR/IFR
later tonight and Mon morning.

KLAX...Low to moderate confidence in TAF. Arrival of cigs tonight
may be off +/- 2-3 hours from TAF with 40% chance of IFR. Cloud
coverage may bounce between SCT and OVC late tonight and Mon
morning. There is also a 20% chance no cigs late tonight. No
significant east wind component expected.

KBUR...High confidence in VFR TAF.

&&

.MARINE...16/848 PM.

Moderate to high confidence in forecast. Current Small Craft
Advisory (SCA) for gusty winds over the outer waters from near
Point Conception southward to San Nicolas Island and in the
vicinity of the Channel Islands looks on track. Good chance for
SCA winds to be ongoing from through much of the week over all of
the outer waters starting Monday evening. Nearshore along the
Central Coast, afternoon through evening SCA winds are likely
Tuesday through Friday.

For the inner waters, SCA winds will affect the western SBA
Channel through late tonight, then subsiding late tonight through
Monday morning before increasing again Monday afternoon and night.
This pattern will continue, with SCA winds in the afternoon and
overnight period, decreasing into the morning hours each day. For
PZZ655, SCA winds are not expected, although local gusts to 25
knots are likely nearshore in the afternoon and evening hours
through Wednesday.

Building short period seas are expected over the next several
days, likely rising to around 7-9 feet over the outer waters.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory in effect from 10 AM Tuesday to 8 PM PDT
      Thursday for zones
      38-88-343>345-351-353-371>373-375-376-379-380-548. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Tuesday for
      zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Wednesday for
      zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Phillips/Gomberg
AVIATION...Phillips/Sirard
MARINE...Ciliberti
SYNOPSIS...Gomberg/Ciliberti

weather.gov/losangeles

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

NWS LOX Office Area Forecast Discussion