Acton Weather

351
FXUS66 KLOX 221101
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
401 AM PDT Tue Apr 22 2025

.SYNOPSIS...22/400 AM.

A cooler weather pattern will continue into Friday as strong
onshore flow and a persistent marine layer will remain in place.
Night through morning low clouds and fog with drizzle will be a
staple of the forecast, struggling to clear from beaches each day.
Gusty onshore winds are possible across the interior portions for
the latter half of the week.

&&

.SHORT TERM (TDY-THU)...22/359 AM.

A well-entrenched low cloud field is in place across the region
this morning as strong onshore flow and a deep marine layer depth
remain over the area. Clouds are pushing into the coastal slopes
of the Coast Ranges along the Central Coast and into the western
portions of the Santa Clarita Valley.

A deepening marine layer depth with stronger onshore flow will be
the driver of the forecast over the coming days as broad troughing
will be anchored along the West Coast. Night through morning low
clouds and fog will be a staple of the forecast into late week.
Clouds will likely struggle to clear from the beaches and
immediate coast over the coming days. Shortwave troughs embedded
in the broader trough will bring the possibility of drizzle,
especially during the late night and early morning hours.

Currently, AMDAR soundings from KLAX indicate a marine layer depth
closing in on 1900 feet deep currently, which is slightly higher
than what NAM BUFR time height sections indicate. The marine
layer depth could top out close to 2500 feet deep this morning,
plenty deep enough to produce at least patchy morning drizzle as
weak dynamics scrape the area. NAM BUFR time height sections
advertise significant deepening of the marine layer depth tonight
through Wednesday morning to around 3000 feet deep. A favorable
flow pattern with height in the boundary layer should bring a
better chance of night through morning drizzle. A deep marine
layer depth with extensive low clouds and fog with drizzle is
likely to persist into Thursday.

The latest surface pressure gradients have moderately strong
onshore pressure gradients remaining in place early this morning,
more than a millibar more onshore than progged. Gradients should
top out close to 9 mb onshore this afternoon, but with another
trough approaching the California coast on Wednesday, the
gradients could approach 10 mb on Wednesday afternoon. Gusty
winds are possible across the interior portion of the area over
the next several afternoon and evenings, and there is a moderate
chance that a wind advisory may be needed for the foothill
portions of the Antelope Valley on Wednesday afternoon and
evening.

With strong onshore flow in place along with a deeper marine layer
depth, a cooler weather pattern will linger into late week. A
deeper marine intrusion will push a cooler air mass well into the
interior portions of the area through at least Wednesday and
likely into late week. Temperatures will likely remain below
seasonal normals into late week.

.LONG TERM (FRI-MON)...22/400 AM.

Broad troughing will linger into late week with a strong trough
expected to move over the region between Friday and Saturday. The
forecast ensembles all indicate cooling extending into Saturday.
EPS ensemble members continue to indicate a majority of the
solutions suggesting precipitation either in the form of light
rain or drizzle on Saturday, while GEFS and CMC ensemble members
are much drier. A cooler and cloudier weather pattern should be
expected for late week.

A warming trend will establish for early next week as cluster
analysis indicates ridging aloft nosing into the region. There is
still quite a bit of ensemble spread due to inconsistencies with
how strong the ridge pattern will be. Most favor a strong ridge
building into the West Coast, possibly bringing above normal
temperatures to the region and weak offshore flow to the Central
Coast. The forecast goes with NBM values for the current time.

&&

.AVIATION...22/1051Z.

At 1000Z at KLAX, the marine inversion was around 1700 feet deep.
The top of the inversion was 2700 feet with a temperature of
16 degrees Celsius.

For 12Z TAF package, high confidence in desert TAFs and moderate
confidence in coastal/valley TAFs. Lower confidence for coastal
and valley sites due to uncertainty with timing of flight category
changes (could be +/- 3 hours of current forecasts).

KLAX...Moderate confidence in 12Z TAF. There is a 20% chance of
IFR CIGs 12Z-16Z. Timing of dissipation of CIGs this afternoon
could be +/- 2 hours of current 20Z forecast. No significant
easterly wind component is expected.

KBUR...Moderate confidence in 12Z TAF. Timing of dissipation of
IFR CIGs could be +/- 2 hours of current 17Z forecast. timing of
return of CIG restrictions this evening could be +/- 2 hours of
current 06Z forecast (with a 40% chance of CIGs dropping to IFR
levels 06Z-12Z).

&&

.MARINE...22/351 AM.

For the Outer Waters, moderate to high confidence in current
forecast. Through tonight, there is a 50% chance of Small Craft
Advisory (SCA) level wind gusts across PZZ670 this afternoon and
tonight with conditions below SCA levels across PZZ673/676. For
Wednesday through Saturday, northwest winds will increase with a
60-80% chance of SCA level winds across all the Outer Waters.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. Through tonight, high confidence
in winds and seas remaining below SCA levels. For Wednesday, there
is a 30-40% chance of SCA level winds in the afternoon and evening
hours. For Thursday through Saturday, there is a 60-70% chance of
SCA level winds, mainly in the afternoon and evening hours.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. Today through Wednesday, high
confidence in winds and seas remaining below SCA levels. For
Thursday and Friday, there is a 40-60% chance of SCA level winds
across the western half of the Santa Barbara Channel. For
Saturday, there is a 60-80% chance of SCA level winds across
western sections of the entire southern Inner Waters.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...Hall
AVIATION...RAT
MARINE...RAT
SYNOPSIS...Hall

weather.gov/losangeles

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