Walnut, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

916
FXUS66 KLOX 191608
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
908 AM PDT Thu Mar 19 2026

.SYNOPSIS...19/852 AM.

Dangerously hot temperatures will continue all week. Coastal
areas likely peaked Tuesday, while valley and interior areas
continue to peak through Friday. Dense coastal fog may is
possible early Friday morning. Temperatures lower significantly
over the weekend, but remain well above normal into next week.

&&

.SHORT TERM (TDY-SAT)...19/907 AM.

***UPDATE***

Light onshore trends continue today which should lead to at least
some minor cooling near the coast. Minimal cooling, if any,
inland and heat advisories and extreme heat warnings continue
through Friday. An area of dense fog moved into the coastal
waters between Catalina and Palos Verdes but so far as been
confined to the ocean. There`s at least an 80% chance that dense
fog will move onshore later tonight as onshore trends are expected
to continue.

***From Previous Discussion***

The dangerous heat wave continues to be on track, at least away
from the immediate coasts. Taking a look at current Satellite
imagery as of 230am, there is a thin line of marine layer clouds
stretching from San Diego into L.A. County (around Palos Verdes),
while marine layer clouds are moving into the coastal waters off
the Central Coast from the north. Why is this important? If the marine
layer clouds continue to roll into the region and spread into the
coastal locations, temperatures will be about 5 degrees lower than
forecast. With the SBA to SAN pressure gradient sitting around
negative 2.1 mb, there is a support for these clouds to continue
moving along the beach areas. Right now the most likely scenario
if the low clouds do continue to move northward, is that areas
around Long Beach, and maybe up to LAX and Santa Monica may get
low clouds and dense fog this morning which in turn could make
temperatures several degrees below the current forecast.
As for valleys and mountains, the inversion is so strong that any
noticeable cooling should be confined to the coastal areas,
meaning hot conditions continue to be on track across the valleys
and mountains.

Besides the marine layer cloud potential becoming more widespread
tonight and Friday morning (however more likely to occur Friday
night into Saturday morning), forecast models are indicating
little change in the diurnal pressure gradients the next few days
with little change in temperatures aloft.

The message continues to be the same as said previously, (through
at least Friday): it continues to be very hot with temperatures
20-30 degrees above normal, and spanning 90-106 degrees away from
the coast and 80s to 90s at the coasts. Heat Advisories and
Extreme Heat Warnings remain in effect through Friday and some
inland hazards may have to be extended.

On Saturday, temperatures are expected to fall a good 5-10
degrees as the ridge shifts into AZ/NM with a short wave trough
starting to move into the region. As a result, there will be an
increase in onshore flow and possible fog near the coast. However,
high temperatures will still be 15-20 degrees above normal.

Record highs for Downtown LA this week are as follows:

Thursday: 97 in 1997
Friday: 93 in 1997
Saturday: 93 in 1931

.LONG TERM (SUN-WED)...19/221 AM.

After the 5-10 degree drop Saturday along with some possible
coastal fog Sunday morning, temperatures will slowly start to
increase again starting Monday through the middle of next week.
Not expecting temperatures to be as hot as this week, but still
15-20 degrees above normal, with a less than 5% chance of
reaching 100 in the valleys.

As for rain chances, the GFS and EC deterministic runs are dry
through the 28th, looking at their respective ensembles and
ensemble AI projections, rain chances were pushed back to the
29th or 30th of March at the earliest. Even then, projections are
still very light in accumulations, and not even close to
significant at this time.

&&

.AVIATION...19/1209Z.

At 0749Z at KLAX, there was no marine layer. The surface-based
inversion top was at 2200 ft with a maximum temperature of 28 C.

High confidence in inland TAFs, low to moderate confidence in
coastal TAFS, with lowest confidence south of Point Conception. There
is a chance of LIFR- VLIFR FG at KLGB (40%), KLAX (40%), KSMO
(35%) KOXR (20%), KCMA (10%), KSBA (10%), KSMX (10%) through 17Z
Thursday. There is a 30-50% chance of VLIFR-IFR conds for coastal
sites after 03Z Fri, highest confidence south of Pt. Conception.

KLAX...Low to moderate confidence in TAF. There is a 40% chance
of 1/4-1/2 FG BKN002 through 17Z Thursday and again after 03Z
Fri. Otherwise high confidence in VFR conditions and any east
winds staying under 6 knots.

KBUR...High confidence in TAF.

&&

.MARINE...19/243 AM.

Conditions are likely to remain below Small Craft Advisory (SCA)
levels through at least Friday. There is a very low to low (10-20
percent) chance for brief SCA level winds for the northernmost
outer waters this evening. SCA conditions are likely to develop
over the weekend across the waters southwest through northwest of
the Channel Islands and the nearshore waters along the Central
Coast. There is a 60-70 percent of widespread SCA conditions by
Saturday evening. There is a low (15-25 percent) chance of GALE
FORCE winds, highest from around Point Arguello south to San
Nicolas Island.

Areas of dense fog across the southern inner waters this morning
will gradually become more widespread through tonight into Friday
morning as a shallow marine layer depth will in place over the
coastal waters.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory remains in effect until 8 PM PDT Friday for
      zones
      38-87-340-341-343-344-346>350-354-355-362-366-367-549-550. (See LAXNPWLOX).
     Heat Advisory in effect until 8 PM PDT Friday for zones
      38-87-343-344. (See LAXNPWLOX).
     Extreme Heat Warning in effect until 8 PM PDT Friday for
      zones 88-342-345-351>353-356>358-368>376-378>380-548. (See LAXNPWLOX).
PZ...NONE.

&&

$$

PUBLIC...MW/Lund
AVIATION...Lund
MARINE...Hall
SYNOPSIS...MW

weather.gov/losangeles

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