Pasadena, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

038
FXUS66 KLOX 231639
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
939 AM PDT Wed Apr 23 2025

.SYNOPSIS...23/926 AM.

A persistent marine layer with stronger onshore flow will keep a
cooler weather pattern in place through Saturday. Night through
morning low clouds and fog with drizzle will be a staple of the
forecast with clouds struggling to clear from beaches each day.
Gusty onshore winds are possible across the interior portions of
the area through the end of the week. A warming trend is expected
for next week.

&&

.SHORT TERM (TDY-FRI)...23/938 AM.

***UPDATE***

The marine layer has deepened to 4000 feet across LA County this
morning based on numerous pilot reports, sloping down to around
2500 ft along the Central Coast. There have been some reports of
drizzle or even light rain, especially in southern Santa Barbara
County and to around La Conchita in far western Ventura County where
amounts of just under a tenth of an inch have been reported.

With this deeper marine layer and an almost 3mb onshore trend it`s
going to be a very slow clearing day, and would not be surprised
if even the LA/Ventura valleys stay socked in well into the
afternoon. Most of the high res models are indicating almost full
clearing today but given past experience with these patterns this
this seems an unlikely outcome. Highs today will mostly be in the
low to mid 60s for coast and valleys.


***From Previous Discussion***

A deep marine layer depth is likely to continue to remain in
place over the coming days as broad troughing remains anchored
along the California coast and strong onshore flow will remain
intact. A cooler pattern will linger into late week with
temperatures below seasonal normals. Weak dynamics aloft will
continue to scrape the area and bring the possibility of night
through morning drizzle.

Across the interior portions of the area, stronger onshore flow
will bring much breezier to windier conditions during the
afternoons and evenings. A wind advisory was added for the western
Antelope Valley foothills for this afternoon and this evening where
gusts up to 45 mph are possible. Isolated gusts to 55 mph cannot
be ruled out near Lake Palmdale. With similar onshore pressure
gradients developing over the coming days, additional wind
advisory headlines may be needed.

By Friday, an elongating trough in the Gulf of Alaska will enter
the region while splitting off from the flow aloft. This cutoff
trough will likely deepen the marine layer depth between Friday
and Saturday to turn it into a deep moist layer up to around 7000
to 8000 feet deep on Friday night. This will be plenty deep enough
to produce night through morning drizzle or light rain across the
region. Mountain showers seems to be a high probability given the
pattern and favorable flow pattern.

.LONG TERM (SAT-TUE)...23/441 AM.

The cutoff trough will approach the California coastline on
Saturday morning as the marine layer mixes out into a deep moist
layer. The forecast ensemble members introduce a majority of the
perturbations with light rain across the area. EPS members are
the wettest relative to the GEFS and CMC ensemble members. Almost
all of the EPS ensemble members have precipitation across the
region with amounts lessening as one heads south. EPS QPF means
suggest a quarter inch or less, with a high chance of values
between 0.25 and 0.50 inch for San Luis Obispo County. Meanwhile,
GEFS and CMC keep the forecast more inline with night through
morning drizzle. Given the cutoff trough, the current forecast
generally keeps NBM values for PoPs, while skewing PoPs higher
along the coastal slopes of the mountains.

Temperatures will be much cooler than normal on Saturday with most
areas being 5-12 degrees below normal. Temperatures in the mid
50s to mid 60s will be common across the coastal and valley areas.
Experimental data analysis on the NBM forecast suggests KLAX and
KOXR potentially seeing record low maximum temperatures on
Saturday. Local records versus the forecast indicate otherwise,
but near record low maximum temperatures will be possible on
Saturday.

A warming trend for much of next week is expected as cluster
analysis still favors an upper-level ridge of high pressure
building into the West Coast. Anomalously high heights seem more
plausible across the Pacific Northwest, but the pattern will still
likely create above normal temperatures with less marine layer
low cloud coverage.

&&

.AVIATION...23/1305Z.

At 12Z at KLAX, the marine layer was 3400 feet deep. The top of
the inversion was at 4700 feet with a temperature of 14 C.

Clouds were widespread across the region, and have pushed into all
areas except for the Antelope Valley, the mountains above 4000
feet, and the far interior valleys of SLO County. Conds were
mostly MVFR to high IFR, except LIFR to VLIFR in the higher
valleys, foothills and lower mountain slopes, with local LIFR
cigs on the Central Coast and in the Santa Ynez Valley.

Expect skies to clear by late morning in the valleys and early
afternoon across interior portions of the coastal plain. Cigs will
likely linger all day the coast, especially south of Pt.
Conception. Expect widespread low clouds tonight, with MVFR cigs
in most areas, except for IFR to VLIFR conds once again in the
higher valleys, foothills and lower mountain slopes.

KLAX...Moderate confidence in TAF. There is a 30% chance that cigs
will scatter out between 20Z and 02Z. There is a 30% chance of an
east wind component of 7 to 9 kt from 10Z-17Z Thu.

KBUR...Moderate confidence in TAF. Cigs may arrive linger until as
least as 21Z today.

&&

.MARINE...23/800 AM.

In the Outer Waters, moderate confidence in the forecast. Winds
will be close to low-end Small Craft Advisory (SCA) levels at
times thru Fri night. SCA conds are likely (60-70% chance) in the
northern zone (PZZ670) this afternoon thru late tonight, while
there is a 40% chance of SCA level winds elsewhere. There is a 40%
chance of low end SCA level winds anywhere across the outer
waters Thu afternoon thru Fri night/Sat morning. SCA level conds
are likely (70% chance) Sat afternoon thru Sun night.

For the Inner Waters north of Pt. Sal, moderate confidence in
the forecast. There is a 40% chance of SCA level winds during the
afternoon/eve hours today thru Fri. SCA conds are likely (60%
chance) during the afternoon/eve hours Sat and Sun.

For the Inner Waters south of Pt. Conception, moderate confidence
in the forecast. There is a 40% chance of SCA level winds during
the afternoon/eve hours today thru Fri in western portions of the
Santa Barbara Channel, then SCA conds are likely there (60%
chance) during the afternoon/eve hours Sat and Sun. Otherwise,
SCA conds are not expected thru Sun night.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 9 PM PDT this evening for zone
      381. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3
      AM PDT Thursday for zone 670. (See LAXMWWLOX).

&&

$$

PUBLIC...MW/Hall
AVIATION...DB
MARINE...DB/Lewis
SYNOPSIS...Hall

weather.gov/losangeles

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