386
FXUS66 KLOX 031316
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
616 AM PDT Mon Jun 3 2024

.SYNOPSIS...03/522 AM.

A warming trend will establish through Wednesday due to high
pressure aloft building in and weakening onshore flow. The warming
trend will be most pronounced away the coast. Hot weather will
develop across the interior for much of this week with
temperatures much above normal for this time of year. Closer to
the coast, the warming trend will be moderated due to continued
night through morning low clouds and fog and moderate to strong
onshore flow.

&&

.SHORT TERM (TDY-WED)...03/517 AM.

Weak and dirty ridging aloft is building into the area early this
morning as the area sits between an downstream upper-level trough
entering the Plains States and an upstream upper-level trough off
the Pacific Northwest coast. A northerly surface pressure
gradient continues to tighten this morning, which has disrupted
the marine layer induced stratus and brought increasing northwest
to north winds to portions of the area. Stratus is well-entrenched
along the Central Coast this morning, but clouds have scoured
south of Point Conception, and mainly only remain across Los
Angeles County. High-resolution multi-model ensemble members
maintain clouds likely spreading back north through the morning
hours into Ventura County and southern Santa Barbara County. An
update might be needed later this morning to touch this part of
the forecast up.

West to northwest winds will develop across southwestern Santa
Barbara County, through the Interstate 5 Corridor, and down into
the western portion of the Antelope Valley through this
afternoon. Then, the winds will turn more northerly and affect
the southeastern portion of Santa Barbara County. Wind advisories
remain in effect for southwestern Santa Barbara County, the
Interstate 5 Corridor, and the western Antelope Valley foothills
for portions of today and tonight, but wind advisories were
expanded into the northern Ventura County mountains for today and
tonight and into the southeastern Santa Barbara County tonight.
There is a moderate to high chance gusty west to northwest winds
reaching advisory levels along the Central Coast and into the
Santa Ynez Valley, through the backcountry portion of the Santa
Barbara County mountains, and across the Antelope Valley floor
west of Highway 14.

Troughing to the north of the area will send quite a bit of middle
and high level cloudiness over the area through Tuesday. The
forecast keep a partly to mostly cloudy stance outside of the
marine layer depth due to the amount of cloudiness pushing south.
Adding confidence to the scenario, a look of infrared imagery
indicates a decent amount of cloudiness moving south this morning
across northern California.

Despite a thinning marine layer depth due to the ridge and the
northerly surface pressure gradient in place this morning, there
is a still a threat of a drizzle. Local 3-km WRF solutions
maintain a favorable flow pattern this morning and Tuesday morning
with weak omega values through the mixed layer. As far as this
morning, though rare, there have been times where ridging aloft
will clamp down on the dense marine air mass and will squeeze out
drizzle. As we move into Tuesday morning, the drizzle makes more
sense conceptually as the dynamics with the trough will lift the
low cloud deck and squeeze out drizzle.

High pressure should start to take control of the pattern on
Tuesday as the trough vacates the region and retreats south of
the U.S. border off the coast of Baja California. High pressure
aloft will build into the region, weakening onshore flow, and
thinning the marine layer depth. The air mass will heat up outside
of the depth of marine layer. A significant warming trend is
forecast for the interior portions of the area between Tuesday and
Wednesday, but the warming trend is more muted along the coast.
Still, there is a moderate chance that low clouds and fog could
get wiped out along the Central Coast between Tuesday and
Wednesday as enough offshore flow could develop. South of Point
Conception, confidence remains high that the marine influence will
remain wedged in and keep the warming trend moderated. Low clouds
and fog could continue to linger into the afternoon hours each
day, keeping the beaches shrouded in cloud cover.

Due to the hot weather forecast early in the month of June, the
climate normals are much lower. An excessive heat watch remains
in effect for Wednesday and Wednesday evening for the interior
portions of the area, such as the interior San Luis Obispo County
valleys, and the Antelope Valley and adjacent foothill areas.
Forecast highs are poised to be close to 15-20 degrees above
normal for this time of year on Wednesday.

.LONG TERM (THU-SUN)...03/521 AM.

A hot weather pattern will continue well away from the coast into
Thursday, and possibly into Friday. The forecast ensembles are
warming temperatures for Thursday and Friday. On Wednesday, NBM
solutions now give a greater chance of 100 and 105 degree high
temperatures for KPMD, KWJF, and KPRB. There is a greater than 95
percent chance of high temperatures reaching 100 degrees out in
the Antelope Valley and a greater than 75 percent chance of KPRB
reaching 100 degrees on Wednesday. On Thursday, a greater than 85
percent chance exists for the Antelope Valley. With the ensembles
trending warmer, the excessive heat watch on Wednesday and
Wednesday evening was extended into Thursday evening.

A southeast flow pattern still develops for late week and could
bring an early start to the monsoon in southern California. While
low confidence exists at this point, the pattern recognition could
come into play for late week or even into the upcoming weekend as
the trough moving to the south will lift back across the area.
Southeast flow aloft will increase and could pipe subtropical
moisture into the region for late week or over the weekend. Forecast
ensemble members have backed off precipitation for Thursday and
Friday, but it remains a non-zero chance given the pattern. There
are a handful of EPS ensemble members giving precipitation for
KPMD and KGXA for Friday through Sunday with NBM solutions giving
a 5 percent chance of rain for Wrightwood-Big Pines on Friday and
through the weekend.

&&

.AVIATION...03/1316Z.

At 12Z at KLAX, the marine layer was 3000 ft deep. The top of the
inversion was at 4300 feet with a temperature of 19 deg C.

Another deep marine layer, but the cloud field was not as solid as
it has been. However, clouds were filling in, and by sunrise,
clouds should be widespread in all coastal and valley areas with
the exception of the portions of southern SBA County, portions of
the valleys of VTU County, and the Cuyama Valley. Clouds were
also pushing into the coastal slopes. Conditions were mostly MVFR
across L.A. County, (except IFR to VLIFR in the foothills), and
IFR to VLIFR from Ventura County northward. Expect skies to clear
by late morning in the valleys, and by early afternoon across the
coastal plain. Clouds may still linger at some beaches today.
Expect a shallower marine layer tonight, with clouds likely
confined to coastal and lower valley areas. Conds will be IFR to
LIFR, except low LIFR in coastal and some lower valley areas of
L.A. and VTU Counties.

KLAX...Moderate confidence in the 12Z TAF. There is a 20% chance
that cigs will scatter out as early as 19Z. There is a 20% chance
that cigs will not return until at least 06Z. There is a 20%
chance of an east wind component of 7-8 kt from 09Z-16Z Tue.

KBUR...Moderate confidence in the 12Z TAF. There is a 20-30%
chance that cigs will scatter out as early as 17Z. There is a 20%
chance that tonight will remain clear.

&&

.MARINE...03/415 AM.

In the outer waters, Small Craft Advisory (SCA) level NW winds
are expected to increase to gales this afternoon (90% chance),
then continue thru late tonight. SCA conds are expected late
tonight thru Tue (90% chance). Winds are expected to drop below
advisory levels in the southern zone (PZZ676) late Tue afternoon
or eve, in the central zone (PZZ673) Wed, and in the northern zone
(PZZ670) late Wed night. SCA level winds are not expected Thu/Fri,
but there is a 50% chance of SCA level seas in northern areas Thu.

In the inner waters N of Pt Sal, steep seas were near advisory
levels this morning, and SCA level NW winds are expected (80%)
chance this afternoon/evening. Winds are seas will likely drop
below SCA levels late tonight/Tue morning, but are likely again
(70% chance) Tue afternoon/eve. SCA conds are not expected late
Tue night thru Fri.

SCA level winds are likely (60-70% chance) in the western third
or so of the SBA Channel this afternoon thru late tonight.
Otherwise, SCA conds are not expected across the inner waters
S of Pt. Sal thru Fri. SE winds will develop late each night and
morning thru Wed or Thu, with isolated winds around 15 knots thru
passages and channels, and between islands.

Steep and choppy seas will likely affect the outer waters thru at
least Wed night, with choppy seas spreading into western portion
of the SBA Channel and the souther inner waters at times.

There is a chance of dense fog in the waters from Point Mugu
northward late tonight thru Thu, mainly during the late night
thru morning hours.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Watch now in effect from Wednesday morning
      through Thursday evening for zones 344-381>383. (See LAXNPWLOX).
     Wind Advisory remains in effect from 3 PM this afternoon to 3
      AM PDT Tuesday for zones 349-351. (See LAXNPWLOX).
     Wind Advisory in effect from 6 PM this evening to 3 AM PDT
      Tuesday for zones 350-352. (See LAXNPWLOX).
     Wind Advisory remains in effect until 3 AM PDT Tuesday for
      zones 377-378-381. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Tuesday for
      zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 3
      AM PDT Tuesday for zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect until noon PDT today for zones
      670-673-676. (See LAXMWWLOX).
     Gale Warning in effect from noon today to 3 AM PDT Tuesday
      for zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Hall
AVIATION...DB
MARINE...DB
SYNOPSIS...Hall

weather.gov/losangeles

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