Sylmar, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

655
FXUS66 KLOX 202121
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
221 PM PDT Sun Apr 20 2025

.SYNOPSIS...20/221 PM.

Expect dry conditions through next weekend, with temperatures
near normal to a few degrees below normal. Low clouds and night
through morning fog will be on the increase early this week
especially near the coast, while mostly clear skies prevail
elsewhere.

&&

.SHORT TERM (TDY-WED)...20/221 PM.

The region will remain beneath broadly cyclonic flow aloft between
a series of impulses tracking across the Pacific Northwest, and a
subtropical stream south of the international border. Patches of
high clouds will be advected over the area as flow peripheral to
the impulses grazes the subtropical stream. However, it will
remain adequately dry in the mid-levels to prevent precipitation
from occurring. Larger-scale pressure gradients will trend
increasingly onshore through early this week, while mean upper
troughing north of the area re-positions westward. This will
foster an increase in low clouds and night through morning fog
especially near the coast. Temperatures will be near normal to a
couple degrees below normal across the region through early and
middle parts of this week, with highs generally in the 70s except
60s near the beaches and lower 80s in parts of the Antelope Valley.

.LONG TERM (THU-SUN)...20/221 PM.

Later in the week and into next weekend, medium-range model
guidance indicates a higher-amplitude trough and perhaps deep
cyclone developing in the vicinity of the Pacific Coast. Model
solutions vary significantly regarding the details of these
features, though perturbation trajectories should remain far
enough inland to minimize precipitation chances. The main effects
from this system will be temperatures cooling by a couple of
degrees late this week into next weekend, as midlevel heights
fall. The falling midlevel heights could also initially support
drizzle development in the deepening marine layer. In addition,
northwest to north pressure gradients will trend offshore as a
result of strong surface high pressure building upstream of the
trough over the Pacific waters. In addition, low clouds and fog
will eventually be shunted southward, becoming confined to LA
County and vicinity -- and perhaps dissipating by next weekend as
cooling aloft with the trough erodes the inversion surmounting
the marine layer.

&&

.AVIATION...20/1747Z.

At 17Z at KLAX, the marine inversion was 1500 feet deep. The top
of the inversion was 2700 feet with a temperatures of 15 degrees
Celsius.

For 18Z TAF package, high confidence in KBUR...KVNY...KWJF and
KPMD. For all other sites, moderate confidence due to some
uncertainties in behavior of marine layer stratus. North of Point
Conception, timing of flight category changes could be +/- 2 hours
of current forecasts. For coastal sites south of Point
Conception, there is a 60-80% chance of IFR/LIFR CIGs and VSBYs
after 06Z tonight.

KLAX...Overall, moderate confidence in 18Z TAF. For tonight,
moderate to high confidence in return of CIG/VSBY restrictions
with timing of return +/- 2 hours of 18Z forecast. No significant
easterly wind component is expected.

KBUR...High confidence in 18Z TAF.

&&

.MARINE...20/1249 PM.

For the Outer Waters, moderate to high confidence in current
forecast. Through Monday, there is a 20% or less chance of Small
Craft Advisory (SCA) level winds around Point Conception. For
Tuesday afternoon through Friday, there is an 80% chance of SCA
level winds across the Outer Waters.

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

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. Through Friday, high confidence in
winds and seas remaining below SCA levels across most areas. The
only exception will be the western half of the Santa Barbara
Channel where there is a 30% chance of SCA level winds Wednesday
through Friday, mainly during the late afternoon through evening
hours.

&&

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

&&

$$

PUBLIC...Cohen
AVIATION...JMB
MARINE...JMB
SYNOPSIS...Cohen

weather.gov/losangeles

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