FXUS66 KLOX 122025
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
125 PM PDT Sat Apr 12 2025

.SYNOPSIS...12/436 AM.

Strengthening onshore flow will bring a cooling trend into early
next week. Night through morning low clouds will become a staple
of the forecast over the weekend, pushing into the coastal slopes
of the mountains by mid week. A cooler weather pattern is expected
through much of next week as a series of low pressure systems move
over the region. Night through morning drizzle or afternoon and
evening mountain showers cannot be ruled out for periods next
week.

&&

.SHORT TERM (TDY-MON)...12/902 AM.

***UPDATE***

The marine inversion was around 1400 ft deep this morning. There
was a good onshore push overnight with 24-hour pressure gradient
trends of +3.3 mb LAX-DAG as of 15Z. A pronounced eddy in the low
cloud field was evident this morning as well, with the center of
the eddy around Santa Barbara Island. Marine layer clouds were
much more organized this morning and covered just about all
coastal areas (exception the SBA County S coast) and pushed inland
to some of the adjacent vlys. Extensive low clouds also covered
the southern Salinas Vly eastward to near the Kern County border.
The low clouds should burn off and clear off the coast this
morning, altho some beaches over L.A. County may have only partial
clearing. Elsewhere and otherwise, mostly sunny skies with some
hi clouds at times can be expected through this afternoon.

There were some gusty N to NE winds this morning over the SBA S
coast around Gaviota and also in the SLO County mtns. Overall,
winds were light to breezy onshore this morning, with all areas
expected to have breezy to gusty W-SW winds this afternoon as
onshore gradients increase thru the day.

Will update the zones to remove dense fog from the VTU/L.A.
County coast and adjacent vlys this morning, otherwise the
forecast in the short-term looks on track.

***From Previous Discussion***

Night through morning low clouds and fog will become a staple of
the forecast as moderate to strong onshore flow is likely to
develop across the region. While gradients will weaken slightly
over the coming days, onshore flow and a well established marine
intrusion will continue. A cooling trend is very likely to persist
through the weekend.

A shortwave trough moving south of Aleutian Islands this morning
will drop down into the region late in the weekend, cutting off
from the flow off the California coast between Sunday and Monday.
This trough will reinforce onshore flow and likely deepen the
marine layer depth. The trough will likely stall out off the coast
for several days and keep a cooler weather pattern in place.

.LONG TERM (TUE-FRI)...12/437 AM.

A series of cutoff troughs of low pressure are expected to move
over the region for next week. There is quite a bit of
uncertainty with the finer details of the forecast. Confidence
remains high in a cooler weather pattern lingering as cluster
analysis suggests a broader troughing pattern lingering through
much of the week. The uncertainty comes from the exact movement of
upper-level low pressure systems. Night through morning drizzle
or mountain showers and thunderstorms cannot be ruled out entirely
given the pattern. The latest forecast ensembles have a few
members generating precipitation for the first trough moving over
the region between Tuesday and Wednesday, but this is likely
underdone due to the convective nature of the air mass. In the
latest deterministic solutions, there are periods of time where a
difluent flow pattern develops ahead of a 500 mb cold pocket
approaching -22 degrees Celsius. The current forecast emphasizes a
deeper marine layer with a cooler weather pattern lingering, but
this will be need to monitored closely.

As we get out into late next week, a stronger cutoff low will
likely move over the region. This could be the system that
could bring a higher chance of precipitation. More than of the
forecast ensembles have QPF with the system for late next week.
There is a also a chance that this system could bring snow levels
down to the 4000 foot level, as well. About a fifth of the EPS
members generate snow for KSDB. As stronger onshore flow will
likely develop with the trough, gusty southwest winds are possible
for the interior portion of the area. EPS wind gusts means
approach wind advisory criteria for several days late next week
for KPMD and KWJF. While the forecast goes with NBM values for the
current time due to the uncertainty, future shifts may need to
take a closer look at the finer details as we get closer into the
time period.

&&

.AVIATION...12/2024Z.

At 1838Z at KLAX, the marine layer was around 900 feet deep. The
top of the inversion was around 2500 ft with a temp of 18 C.

High confidence in desert TAFs, moderate confidence in KPRB, and
low to moderate confidence in remainder of sites. Timing of flight
cat changes may be off by +/- 3 hours, with cigs arriving at KOXR,
KCMA, KSMO, KLAX, and KLGB as early as 21Z. Cigs may arrive and
scatter multiple times before remaining at the TAF site after 06Z. There
is a 30% chc of VLIFR conds at KSBP and KSMX. IFR conds are
possible upon arrival at sites south of Point Conception, lifting
to low MVFR by 12Z-15Z Sun. Cigs may struggle to clear and remain
at the coastal TAF sites through the period.

KLAX...Low to moderate confidence in TAF. There is a 30% chance
that cigs arrive as early as 21Z, and scatter and reform
frequently until remaining at TAF site after 06Z. There is a 30%
chance of BKN008 conds until lifting to BKN010-015 after 12Z. There
is a 40% chance that cigs linger until 20Z Sun. No significant
east wind component expected thru the period.

KBUR...Low to moderate confidence in TAF. There is a 30% chance
that cigs this evening will arrive as early as 07Z and clear as
late as 19Z. There is a 30% chance of cigs arriving as BKN006 and
lifting to BKN010-015 by 12Z-15Z.

&&

.MARINE...12/856 AM.

For the outer waters, low-end GALE force wind gusts are expected
thru this evening. Thereafter, Small Craft Advisory (SCA) level
winds and seas are expected thru Sunday, with SCA level seas
likely lingering into Sun evening. SCA conds are not expected late
Sun night thru Wed.

For the inner waters N of Pt Conception, SCA level seas will
likely continue thru tonight. Winds will likely (80% chance) reach
SCA levels this afternoon/eve, with a 20% chance of GALE force
gusts. SCA conds are not expected Sun thru Wed night.

For the Santa Barbara Channel, SCA level winds are likely (70%
chance) in western portions this afternoon thru late tonight, with
a 30% chance of SCA winds pushing into eastern portions. SCA
conds are not expected Sun thru Wed night.

For the southern inner waters, there is a 30% chance of SCA level
W-NW wind gusts this afternoon/eve from Anacapa Island to Malibu,
and a 20% chance of SCA winds pushing into the Santa Monica Basin
and across the outer portion of the zone. Otherwise, SCA conds
are not expected thru Wed night.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect until 9 PM PDT this evening
      for zones 87-354-362-366-367. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Sunday for
      zones 645-650. (See LAXMWWLOX).
     Gale Warning in effect until 9 PM PDT this evening for zones
      670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Hall/Sirard
AVIATION...Lund
MARINE...DB/Lund
SYNOPSIS...Hall

weather.gov/losangeles

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