Topanga, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

527
FXUS66 KLOX 190440
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
840 PM PST Thu Dec 18 2025

.SYNOPSIS...18/750 PM.

Well above normal temperatures will continue away from the coast
through Friday. Unsettled weather is possible this weekend along
the Central Coast, spreading to all areas with a potentially
significant storm near the middle of next week.

&&

.SHORT TERM (THU-SUN)...18/839 PM.

***UPDATE***

Quite the impressively warm day today as high pressure aloft with
above normal hgts and offshore flow combined to rise temps across
the LA/VTA csts and vlys by 8 to 12 degrees. Elsewhere the SBA
south coast saw a remarkable 12 to 18 degrees of warming. There
was little change or even some cooling across the rest of SBA
county and all of SLO county as the offshore push there relaxed
and some cool air moved int from the interior. Max Temp records
were set at Woodland Hills (92) Santa Barbara (84), Palmdale and
Lancaster (both 75).

Current satellite imagery does not show much in the way of low
clouds but all short range mdls and ensembles do show plenty of
low clouds moving into the LA cst, western SBA county and the Paso
Robles area.

Current short term forecast looks on track and no updates are
planned.

***From Previous Discussion***

On Friday the ridge will be pushed to the south and flat westerly
flow sets up over the area. Hgts will fall to about 585 dam
(still well above normal). Low clouds will be similar to Wednesday
and pretty much confined to the Long Beach area. Much weaker
offshore flow at the sfc will lead to 3 to 6 degrees of cooling
across the csts/vlys. The lack of cool air advection from the
San Joaquin Vly will lead to 2 to 4 degrees of warming across the
interior.

Flat westerly flow continues over the area on Saturday. Hgts will
dip down to 582 dam. Onshore flow to the east will increase from 1
mb in the morning to about 3 mb in the afternoon, the offshore
flow from the north will be 3 mb weaker in the afternoon compared
to Friday. The onshore flow and falling hgts will bring some
coastal low clouds to the area in the morning. At the same time the
southern edge of an atmospheric river (AR) affecting the northern
portion of the state will move south enough to south to bring
mostly cloudy skies to most over the area save for LA County which
will end up partly cloudy. The AR could (20 percent chc) bring
some light rain to SLO county. The cooling trend will continue as
falling hgts and better onshore flow combine to lower most temps 3
to 6 degrees. The Central Coast will be the exception with little
change in temps. Max temps, however, will remain above normal
(3 to 6 degrees csts, 5 to 10 degrees vlys and 10 to 15 degrees
mtns and far interior).

.LONG TERM (MON-THU)...18/201 PM.

Tuesday remains the day of transition. The AR will sag south and
the flow will become even more southwesterly. Rain chances will
overspread the entire area. Rain chances have increased with the
latest forecast and now sit around 40 percent for LA county, 50
percent for VTA county, 50 to 60 percent for SBA county and 60 to
70 percent for SLO county. The forecast rainfall amounts have also
been increased. SBA and SLO counties will now likely see a half
inch to an inch of rain, while a quarter inch to a half inch is
possible for VTA and LA counties.

There has been a slight change in the current thinking for the
Wed/Thu storm. Both the EC and esp the GFS (as well as most
ensembles and the AI enhanced mdls) are now speeding up the system
(hence the wetter Tuesday fcst). This forecast (Which very well
might change since it is 7 to 8 days away) now call for the bulk
of the rain to fall Wednesday through Thursday (Christmas)
morning. Very preliminary (and subject to change) rainfall totals
for the Wed/Thu time period call for 2 to 4 inches of rain
csts/vlys, 4 to 6 inches across the mtns and 1 to 2 inches for the
interior sections. It is too early to get a handle on rainfall
rate predictions. Snow levels will be over 8000 ft but will start
to fall later Thursday.

Model agreement falls off pretty rapidly after Thursday, but there
is a potential for another system over the weekend of the 27th and
28th.

&&

.AVIATION...18/2214Z.

At 2200Z at KLAX, the marine layer depth was around 400 feet.
The top of the inversion was 2000 feet with a temperature of
25 degrees Celsius.

For the 00Z TAF package, high confidence in KSBP...KSBA...KOXR...KCMA
KBUR...KVNY...KPMD and KWJF.

For KSMX...KLAX...KLGB and KLGB, moderate confidence in 00Z TAFs
as timing of flight category changes with marine layer could be
+/- 3 hours of current forecasts.

KLAX...Overall...moderate confidence in 00Z TAF. Timing of flight
category changes could be +/- 3 hours of current forecasts. No
significant easterly wind component is expected.

KBUR...High confidence in 00Z TAF.

&&

.MARINE...18/740 PM.

For the Outer Waters, moderate to high confidence in current
forecast. Tonight through Friday evening, Small Craft Advisory
(SCA) level winds will continue across all of the Outer Waters.
For Friday night and Saturday, the SCA level winds will continue
across PZZ673/676. Additionally, there will be 20% chance of Gale
force wind gusts at times around Point Conception through
Saturday. For Sunday through Monday, winds and seas will remain
below SCA levels for all of the Outer Waters. For Tuesday, there
is a 60-80% chance of SCA level southeasterly winds.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. Through Friday, there is a 50-70%
chance of SCA level winds in the afternoon and evening hours. For
Saturday through Monday, high confidence in winds and seas
remaining below SCA levels. For Tuesday, there is a 40-50% chance
of SCA level southeasterly winds.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. Through Friday, there is a 50-70%
chance of SCA level northwest winds across the western half of
the Santa Barbara Channel, mainly during the late afternoon and
evening hours. Otherwise, high confidence in winds and seas below
SCA for the southern Inner Waters through Monday. On Tuesday,
there is a 30-50% chance of SCA level southeasterly winds.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 9 PM PST Friday for zone
      670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 AM PST Saturday for
      zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Rorke/Rorke/RM
AVIATION...RAT
MARINE...RAT/Ciliberti
SYNOPSIS...RM/jld

weather.gov/losangeles

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