727
FXUS66 KLOX 250359
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
859 PM PDT Tue Sep 24 2024

.SYNOPSIS...24/633 PM.

Low clouds and fog will continue across coastal areas through the
week with some afternoon clearing and below normal temperatures.
Valley temperatures are expected to be at or below normal for the
remainder of the week, while the far interior areas will remain
above normal. Otherwise, a quiet weather pattern will continue.

&&

.SHORT TERM (TUE-FRI)...24/647 PM.

***UPDATE***

A quiet weather pattern will continue tonight into Wednesday.
Temperatures are expected to drop between 3 to 8 degrees compared
to today, most notably over the mountains and valleys. Onshore
flow is expected to continue as a weak upper low remains off the
coast, contributing to the cooling trend as heights lower aloft.

This evening, gusty southwest winds are affecting some passes
and canyons, including the LA county interior into the Antelope
Valley, and also some canyons in the Santa Monica Mountains.

At the coast, low clouds associated with the marine layer are
already covering much of the coastal sections, and clouds are
expected to progress well inland over the coastal valleys
overnight into Monday morning.

***From Previous Discussion***

Big cool down today across the valleys, several degrees more than
expected, as a big increase in the onshore flow to the north
(LAX-BFL) brought a solid cloud layer farther inland and it was
slow to clear. The result was a 6-12 degree drop in high temps
there. In an odd twist areas that were within 5 miles of the
coast were slightly warmer than yesterday. As was the Antelope
Valley and interior SLO County.

The deterministic models indicate weakening onshore flow Thu/Fri
but ensemble based guidance shows little change in temperatures
the rest of the week, meaning onshore flow will likely change
little through the period. Overall a quiet period of weather this
week that will likely carry into the weekend and possibly into
early next week.

.LONG TERM (SAT-TUE)...24/158 PM.

Longer range ensembles continue to show a weak upper low lingering
just off the coast through the weekend and into early next week
but with some height rises as high pressure tries to build in from
the southeast. However, given the rather large spread in the
ensemble solutions confidence is lower than usual with the
specifics during this period. Probably no significant warming
trends coming, but a few degrees of warming is possible, mainly
away from the coast as onshore flow is expected to be fairly
strong later in the period.

&&

.AVIATION...25/0048Z.

At 0030Z at KLAX, the marine layer was 1500 ft deep. The top of
the inversion was near 2200 ft with a temperature of 28 deg C.

High confidence in IFR or lower cigs/vsbys for coastal TAFs with
low confidence in timing of return to VFR with a 10-30% (highest
nearest the coast) chance that of brief or no return to VFR conds
occur.

Moderate confidence in valley TAFS (KBUR/KVNY/KPRB) with a 10-20%
chance VFR conds prevail for KBUR/KVNY and a 20% chance of IFR
conds KPRB (10-18Z).

High confidence in KPMD and KWJF TAFs.

KLAX...Moderate confidence in TAF. There is a 10% chance for
VV002 cigs and/or vsbys 1/2SM or lower between 04Z and 15Z.
However, there is also a 20% chance for cigs to remain OVC005 or
higher thru the period. High confidence in no significant east
wind component.

KBUR...Moderate confidence in TAF. There is 10% chance VFR conds
prevail thru the period.

&&

.MARINE...24/858 PM.

A low end Small Craft Advisory has been issued for the southern
Inner Waters and southern Outer Waters and is in effect late
Wednesday afternoon through early evening.

For the Outer Waters (Central Coast south to San Nicolas Island),
moderate to high confidence in the forceast. High confidence in
the northern zone (10 to 60 NM off the Central Coast) remaining
below Small Craft Advisory (SCA) level thru Thursday, then there
is a 40-60% chance of SCA winds Thurs afternoon thru evening. In
the two Southern Zones (Pt Sal to San Nicolas Islands), moderate
confidence in conditions remaining sub advisory thru Wednesday
afternoon. Then there is a 40-60% chance of SCA level winds form
Pt Conception to San Nicolas Island in the afternoon thru evening
Wednesday and Thurs. Then, moderate confidence in the Outer
Waters remaining sub advisory Friday thru late Saturday, then
increasing to SCA level thru late Sunday.

For the Inner Waters along the Central Coast, moderate to high
confidence in conditions remaining sub advisory thru the period,
with highest chances (20-40%) of SCA conditions Thurs afternoon
thru evening and late Sat thru late Sun.

For the Inner Waters south of Pt Conception, moderate confidence
in winds and seas remaining below SCA level thru Wednesday
morning. Moderate confidence (50-70% chance) in SCA level winds in
Santa Barbara Channel and from Anacapa Island to Pt Dume and the
San Pedro Channel Wednesday late afternoon thru early evening.
Then, moderate confidence in winds remaining sub advisory thru
Sunday, and increasing Sunday afternoon thru evening in the
Western Portion of the Santa Barbara Channel.

A shallow marine layer will bring at least patchy dense fog thru
Wednesday, especially in the afternoon thru evening hours. Please
refer to our marine weather statement for more information.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 2 PM to 9 PM PDT
      Wednesday for zones 650-655-676. (See LAXMWWLOX).

&&

$$

PUBLIC...MW/Smith
AVIATION...Munroe/Lewis
MARINE...Lewis/Munroe
SYNOPSIS...MW/Smith

weather.gov/losangeles

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