727
FXUS66 KLOX 291853
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1153 AM PDT Sat Jun 29 2024

Updated Aviation and Marine Sections

.SYNOPSIS...29/450 AM.

A general warming trend will establish across the area through
next week as high pressure aloft strengthens over the region. Warm
temperatures over the area this weekend will likely turn
dangerously hot across the interior toward the middle of next
week. Near record heat is possible between Independence Day and
Saturday, especially across the mountains and desert. A hot air
mass could linger into next weekend.

&&

.SHORT TERM (TDY-MON)...29/847 AM.

***UPDATE***

The forecast is well on-track, and no changes have been made to
the ongoing forecast.

***From Previous Discussion***

Low clouds and fog are well-entrenched across the coast and lower
coastal valleys this morning as moderate onshore flow remains in
place. Stronger onshore pressure gradients brought some cooling
on Friday, which led to more cloud coverage across the area last
night and into this morning. While the coastal areas will see
temperatures closer to persistence today, a warming trend will
develop outside the marine influence as 500 mb heights climb
across the region through the weekend.

Earlier AMDAR soundings from KLAX indicated the marine layer
depth around 950 feet deep around midnight, which did agree well
NAM BUFR time height sections. If the NAM BUFR time heights
section played out as progged, the marine layer depth has likely
deepened to close to 2000 feet deep at KLAX. This is partially due
to the influence of weak troughing to the northwest of the area
and the eddy circulation still intact across the southern
California bight. Actually, several eddy vortices can be seen on
satellite early this morning, including one into the Santa Barbara
Channel.

Clouds could struggle to clear from the beaches today, but with
the high pressure building in, the marine layer depth will shrink
and thin rapidly throughout the late morning hours. Outside of the
marine intrusion, the air mass will heat up across the region.
EPS, GEFS, and CMC ensemble members solutions suggest a steady
warming trend taking shape through Sunday. Closer to the coast due
to the persistent marine layer depth, the warming trend will be a
bit more muted, with less warming likely taking place.

With the marine layer turning more shallow through tonight and
into Sunday morning, there is a moderate-to-high chance that any
low clouds and fog could form dense fog across the coastal areas.
High-resolution multi-model ensemble members suggest a 40-50
percent chance of dense fog developing along the Central Coast and
into the Los Angeles County beaches by daybreak Sunday.

By Monday, the upper-level ridge of high pressure over north Texas
this morning will push a bit to the east and allow for a weak
upper-level trough over the North Pacific to drop into the Pacific
Northwest. This trough should bring slight height falls and an
increase in onshore flow. As a result, low clouds and fog could
become more pronounced on Monday or Monday night, and the warming
trend should level off, or maybe see a degree or two of cooling
across the area.

.LONG TERM (TUE-FRI)...29/457 AM.

High pressure aloft will quickly lift the trough out of the region
and build into the region from the west. Strong ridging over the
North Central Pacific Ocean will build into the state through
Friday. While there is still quite a large spread in the model
solutions over how warm it will get and the strength of the high,
the forecast ensemble members favor a very warm to hot air mass on
Tuesday turning much hotter by Friday. Temperatures break away
from NBM values in the extended period to advertise near record
heat between Independence Day and Saturday. Record heat is
introduced for Friday in the latest forecast with forecast
temperatures of 111 degrees at Paso Robles and 114 degrees at
Palmdale and Lancaster, with daily record values at 110 and 113
degrees respectively. While the hottest temperatures and highest
likelihood of record high temperatures will be for the interior
portions of the area, it should be noted that Woodland Hills
Pierce College has a lower record high for July 5th. The record
high for Pierce College is 105 degrees on July 5th, bookended by
a 112 degree record high on July 4th and a 116 degree record high
on Saturday, July 6th. The forecast currently advertises a tie of
the record high for July 5th, but there is a moderate chance that
this record could be broken.

With the near record high temperatures expected and very warm
overnight low temperatures forecasted, an Excessive Heat Watch
remains in effect for the interior portions of the area as
dangerously hot weather could develop causing heat stress and a
higher likelihood of heat illness for anyone planning outdoor
activities.

The forecast keeps some semblance of a low clouds field near the
coast into late week, but there is a moderate chance that low
clouds and fog could be very patchy in nature given the high
pressure center location. If any monsoonal moisture sneaks in from
the southeast, the low cloud field could become non-existent as
the clouds aloft will play tricks on the marine inversion.

The latest EPS ensemble precipitable water value means continue
to trend higher in the latest runs with the potential for
monsoonal moisture. EPS PWAT means now exceed above 1.00 inch
between Wednesday and Thursday. There are handful solutions
offering a higher spread into the weekend and into early next
week. Any increase in cloud cover could put a damper of excessive
heat developing, especially if a thick cloud shield develops and
cuts into temperatures. Though unlikely at this time, very slight
chance PoPs remain in the forecast for each afternoon and evening
from Wednesday through Friday across the interior portions of the
area. As the forecast ensembles are at the mercy of convective
parameters working as advertised, it is a low confidence but high
impact type scenario. Stay tuned at this could become a wrinkle
in the forecast.

&&

.AVIATION...29/1851Z.

At 16Z at KLAX, the marine layer was 1800 feet deep. The top of
the inversion was at 4500 feet with a temperature of 22 Celsius.

Low confidence on clearing at KSBA and KOXR this afternoon. Most
likely VFR conditions will occur by 21Z, but clearing could occur
as early as 19Z or as late as 23Z if at all. Otherwise, moderate
confidence in VFR at all other sites by 18Z. High confidence in
VFR conditions through Sunday at KPRB KBUR KVNY KWJF KPMD. High
confidence in lower ceilings and visibility with less low cloud
coverage tonight compared to last night. Low confidence in timing
and which airports will get ceilings tonight into Sunday. Chances
for ceilings: KSBP (30% LIFR) KSMX (60% LIFR) KSBA (40% LIFR)
KOXR (40% LIFR, 20% IFR) KCMA (40% LIFR, 20% IFR) KSMO (30% LIFR
40% IFR) KLAX (30% LIFR 40% IFR) KLGB (20% LIFR 50% IFR). Cannot
discount VLIFR anywhere, especially KSMX KSBA.

KLAX...Moderate confidence in VFR conditions through at least 02Z.
Moderate confidence on ceilings occurring tonight, high confidence
in ceilings being at least IFR with a 30% chance of LIFR. Cannot
discount a few hours of VLIFR dense fog. Low confidence on timing
with ceilings starting as early 02Z and as late 10Z. High
confidence in any southeast winds staying under 06 knots.

KBUR...High confidence in VFR conditions through Sunday with a
less than 10% chance of ceilings after 10Z. High confidence in
seasonal winds.

&&

.MARINE...29/946 AM.

High confidence in dense fog (with visibilities one nautical mile
or less) affecting the waters off of Santa Barbara and San Luis
Obispo Counties this morning and likely through the afternoon and
evening. There are indications that the fog will scour out as the
northwest winds increase later tonight.

High confidence in fairly benign conditions everywhere through
early this evening, except for lingering choppy seas. High
confidence in northwest winds increasing quickly tonight into
Sunday and lasting through Monday Night. For the offshore waters
from the Central Coast to Point Conception, There is a 70% chance
of Gales by Sunday afternoon and night, with a small but present
chance on Monday. Otherwise, high confidence in Small Craft
Advisory winds from the Central Coast to San Nicolas Island. There
is also a low but present threat of these winds pushing deep
enough into the Santa Barbara Channel to need a Small Craft
Advisory, but the more likely outcome is for those winds to stay
confined to the far western portion. As a result of these winds,
expect building choppy seas over most waters, even those areas
that are not very windy.

Moderate confidence for significantly and abnormally light winds
Tuesday and Wednesday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Watch in effect from Tuesday morning through
      late Friday night for zones
      38-88-343>345-353-376>379-381>383. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 9 PM this evening to 3 PM
      PDT Sunday for zone 670. (See LAXMWWLOX).
     Gale Watch in effect from Sunday afternoon through late
      Sunday night for zones 670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 AM to 3 PM PDT Sunday
      for zone 673. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 AM Sunday to 3 AM PDT
      Tuesday for zone 676. (See LAXMWWLOX).

&&

$$

PUBLIC...Hall/Cohen
AVIATION...RK
MARINE...Kittell
SYNOPSIS...Hall

weather.gov/losangeles

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