277
FXUS66 KLOX 231628
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
928 AM PDT Mon Sep 23 2024

.SYNOPSIS...23/837 AM.

Low clouds will affect the coastal areas through the week with
near normal temperatures, and dense fog through at least Tuesday.
Inland temperatures will remain above normal through the week,
warmest today through Tuesday. Otherwise, fairly benign pattern.

&&

.SHORT TERM (TDY-WED)...23/822 AM.

***UPDATE***

The marine layer is currently between 800 and 1200 feet, but in
many ways it is behaving likely it is much shallower than that.
Thick fog with visibilities under 1 mile is affecting a lot of
the coastal and adjacent valley areas. The most widespread dense
fog with visibilities of 1/4 mile or less is occurring over the
Central Coast and the Santa Ynez Valley, where a Dense Fog
Advisory was issued through 10am today. Expecting most areas to
see visibilities starting to improve within the next hour and
clear to at least the beaches by 11am. Where the low clouds and
fog will be this afternoon is a tough call. The offshore pressure
trends suggest good clearing and some projections show some sort
of clearing trend from northwest to southeast. Looking at the
satellite picture however and the late morning cloud surge has the
scent of poor beach clearing from the Central Coast to Ventura
County.

While coastal areas will likely see similar temperatures compared to
yesterday thanks to the moderating effects of the marine layer,
all other areas will be 5 to 10 degrees warmer thanks to those
offshore pressure trends and building high pressure aloft. The
current temperature forecast looks on track with highs in the mid
80s to mid 90s common away from the immediate coast, and the
hottest spot or two approaching 100 degrees.

***From Previous Discussion***

The marine layer will be a little shallower tonight and there will
be a little less clouds in the vlys. The csts, however, will
remain mired in stratus with patchy dense fog.

Not much excitement in the Tue/Wed fcst. At the upper levels SW
flow will develop over the state as a trof forms in the E PAC and
a high amplitude ridge develops over the Rockies. Tuesday`s 586
dam hgts will fall to 584 dam. There will be similar gradients
Tuesday and a stronger onshore push to the east on Wed.

The low cloud pattern will continue across the coasts each night
through morning with a little more vly penetration on Wed due to
the increase in onshore flow.

There will not be too much change in temps on Tuesday. The
interior will warm a little making Tuesday the warmest day there.
Most coastal areas will cool a degree or two. The lowering hgts
and increased onshore flow will combine to bring 3 to 6 degrees of
cooling to the area on Wednesday. The marine layer will bring a
split personality to temps on Wed with the csts/vlys 2 to 4
degrees blo normal and the interior 4 to 6 degrees above normal.

.LONG TERM (THU-SUN)...23/313 AM.

The GFS and EC ensembles and deterministic runs are in good
agreement thru the xtnd period. Srn CA will be in between high
pressure to the east and low pressure troffing to the west. SW
flow aloft will continue through the period.

Quiet weather will dominate the fcst. In fact it will be rather
June like with the forecast confined to how much marine layer
stratus there will be each night through morning.

Those low clouds should cover the coasts each night through
morning with perhaps a little better vly coverage Sunday as the
onshore flow is forecast to increase to mdt-stg.

Look for slight warming Thu and better warming Fri. Cooling is on
tap for both days Sat and Sun. Max temps will continue cooler than
normal across the csts/vlys and warmer than normal across the
interior.

&&

.AVIATION...23/1041Z.

Around 0830Z, the marine layer depth was near 1000 feet deep at
KLAX. The top of the inversion was around 3100 feet with a
temperature of around 27 degrees Celsius.

High confidence in the current forecast for valley and desert
terminals. Moderate confidence in the current forecast for the
coastal terminals.

For coastal terminals, LIFR conditions will be common terminals
through 15Z, then conditions improve one category through 17Z.
There is a moderate-to-high chance of VLIFR conditions through
14Z. Conditions should improve to VFR between 17Z and 19Z, but
there is a low-to- moderate chance that IFR to low MVFR conditions
remain in longer than expected. An early return of LIFR to IFR
conditions should be expected with conditions deteriorating as
soon as 01Z.

For all other terminals, VFR conditions are expected, except
for a low-to-moderate chance of VLIFR conditions for Los Angeles
San Fernando Valley terminals.

KLAX...LIFR conditions will be common through 15Z, then
conditions improve one category through 17Z. There is a 30 percent
chance of VLIFR conditions through 14Z. The current forecast
reflects surface visibility and not tower visibility. Conditions
should improve to VFR as early as 19Z, or as late as 22Z. There
is a 30 percent chance that IFR to low MVFR conditions will
persist through the afternoon hours. LIFR to IFR conditions
should spread back into KLAX as soon as 01Z or as late as 03Z.

KBUR...There is a 30 percent chance of VLIFR to LIFR conditions
through 16Z, otherwise VFR conditions are expected.

&&

.MARINE...23/928 AM.

High confidence in the current forecast through early Thursday,
then moderate confidence thereafter. Winds and seas will remain
below Small Craft Advisory (SCA) levels through early Thursday,
except for low-to-moderate (20-30 percent) chance of local SCA level
W-NW wind gusts in the vicinity Point Conception, near Point Dume
and into the San Pedro Channel each afternoon and evening through
Wednesday. There is a moderate (40-50 percent) chance of SCA
level winds Thursday afternoon through Friday for the waters
beyond 10 NM offshore along the Central Coast southeast to San
Nicolas Island. Additionally, there is a 30% chance of SCA level
seas building over the weekend.

A shallow marine layer over the coastal waters will bring at
least patchy dense fog to the coastal waters at times through
Wednesday morning. A marine weather statement is in effect through
noon today, but there is a likely chance that areas to widespread
dense fog will redevelop over the coastal tonight through Tuesday
morning.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Dense Fog Advisory in effect until 10 AM PDT this morning for
      zones 340-341-346>348. (See LAXNPWLOX).
PZ...NONE.

&&

$$

PUBLIC...Rorke/Kittell
AVIATION...Hall
MARINE...Hall/Lund
SYNOPSIS...Kittell

weather.gov/losangeles

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