Walnut, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

746
FXUS66 KLOX 311028
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
328 AM PDT Sat May 31 2025

.SYNOPSIS...31/208 AM.

Cooler but more humid conditions this weekend as tropical
moisture moves over the region, with a chance for showers or a
thunderstorm. Near normal conditions will follow Monday and
Tuesday, with a modest warm up towards the end of next week.

&&

.SHORT TERM (TDY-MON)...31/319 AM.

The latest satellite is showing a rapidly expanding marine layer
which is now blanketing all coastal sections. While visibilities
under one mile will affect the Central Coast once again (a Dense
Fog Advisory will be considered), the rest of the area should not
see much fog. This should remain the case through most of the
morning hours. For the afternoon, with onshore pressure gradients
peaking in the 9 millibar neighborhood (both west to east and
south to north), many coastal areas should see slow to no
afternoon clearing - unless convection starts firing which almost
always disrupts the marine layer (more on that later).

The Heat Advisories have completed their run as temperatures
remain on track to lower over the weekend. Temperatures will stay
above normal however, and will still feel warm as humidity rises
with the advance of tropical moisture from the south. Some might
even say that it feels muggy by tonight. This moisture draw is
due to an upper level cut off low, with a center currently stalled
400 miles south of Los Angeles, generating steady southeast flow
aloft. Whenever we deal with a tropical moisture surge, we
instantly look to the shower and thunderstorm chances. The other
two key ingredients are there, instability (MUCAPE 500-1000+ and
K-Index 35-40) and potential kickers (500 millibar vorticity
disturbances and omega values of 10+). While most of the computer
models are scant on rainfall, the high resolution CAMs are
resolving some reflectivity returns which gives us a little
confidence that something will form somewhere. For this afternoon,
models continue to highlight the mountains along the Santa
Barbara and Ventura County border, which should get the best mix
of sunshine and elevated moisture. To the east, ample clouds will
be streaming in which will limit afternoon heating, but being
closest to the moisture source, a shower or two cannot be ruled
out. For tonight and Sunday, the shower chances will expand over
most of Los Angeles and Ventura Counties as the moisture peaks and
several upper level disturbances rotate through. The most likely
scenario is for much of the area to see a few inconsequential fat
drops falling from the sky, but a spot or two or three will get a
legit but brief shower. Cannot discount a thunderstorm or two as
well, especially over the San Gabriels and Antelope Valley thanks
to the favorable northeast steering flow by Sunday.

The vast majority of projections have the low quickly pushing east
Sunday night as another upper level low drops into northern
California, with the moisture feed shutting down fast. As that
next low rotates through southern California Monday and Tuesday,
the ingredients are in place for more June-like weather to return
with a marine layer covering most coastal and valley areas, and
gusty southwest winds over the interior.

.LONG TERM (TUE-FRI)...31/321 AM.

Little change expected from Monday through Wednesday, with
typical June Gloom conditions on the coastal side of the ranges,
and breezy warm conditions on the desert side. Ensemble
projections show a range of outcomes for the back half of next
week, ranging from little change to a modest warm up as the flow
turns more northwesterly.

&&

.AVIATION...31/0533Z.

At 0438Z, the marine layer was 1500 feet deep at KLAX. The top of
the inversion was around 2000 feet with a temperature of 29 C.

Overall, low to moderate confidence in the 06Z TAF Package. High
confidence for desert and valley terminals and low for coastal
sites. Timing of cig/vsby restrictions may be off +/- 3 hours and
minimum flight cats off by one or two.

KLAX...Low confidence in 06Z TAF. There is a 30% chance of LIFR
cigs (BKN/OVC002-004) through 15Z Sat. Departure of cigs may be
off +/- 2 hours. No significant east wind component expected.

KBUR...Moderate confidence in 06Z TAF. There is a 20% chance for
LIFR to IFR conds (likely short-lived) through 16Z Sat.

&&

.MARINE...31/322 AM.

For the outer waters, moderate to high confidence. Small Craft
Advisory (SCA) conditions are lingering tonight for PZZ673 due to
steep, short period seas. Conditions are then expected to remain
below SCA levels through early Sunday morning. There is a 50-60%
chance of SCA level wind gusts in PZZ670 from Sunday afternoon
into the overnight hours. Higher confidence in seas reaching 10 ft
through Monday evening. Thereafter, conditions look to remain below
advisory criteria through at least mid-week.

For the nearshore waters along the Central Coast, conditions are
expected to remain below SCA criteria through mid-week. However,
there is a 30% chance for SCA level seas Sunday evening into late
night.

For the Santa Barbara Channel, high confidence in conditions
remaining below SCA criteria through the mid-week. However,
there is a 20% chance of SCA level wind gusts over the western
portion during the afternoon and evening hours on Sunday.

For the Inner Waters off the Los Angeles and Orange County coasts,
high confidence in conditions remaining below SCA levels through
Wednesday.

Brief, localized SCA wind gusts may occur across the coastal
waters Saturday afternoon through Sunday morning as an upper level
low pressure system off the coast of Baja California moves north
then east over our coastal waters. This system brings a 10-20%
chance of thunderstorms Saturday afternoon through Sunday,
especially south of Point Conception.

As the system exits the region, another upper-level low pressure
system will dive south over the coastal waters Sunday into Monday
bringing chances for SCA seas, weaker winds, and a deepening
marine layer with drizzle at times.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Dense Fog Advisory in effect until 9 AM PDT this morning for
      zones 340-346-347. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 5 AM PDT early this
      morning for zone 673. (See LAXMWWLOX).

&&

$$

PUBLIC...Kittell
AVIATION...Black
MARINE...Black/Phillips
SYNOPSIS...RK

weather.gov/losangeles

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