-- Discussion containing changed information from previous version are highlighted. --
596
FXUS66 KLOX 111611
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
911 AM PDT Tue Jun 11 2024

.SYNOPSIS...11/151 AM.

Temperatures today are expected to warm a few more degrees as
high pressure builds and onshore flow weakens. As an upper low
moves through the region, cooler temperatures and a deeper marine
layer are expected Wednesday and Thursday. Friday through the
weekend daytime highs will trend upward with locally gusty
northerly winds.

&&

.SHORT TERM (TDY-THU)...
-- Changed Discussion --
11/910 AM.

***UPDATE***

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

***From Previous Discussion***

The marine layer is shallower tonight compared to last night,
currently about 1500 ft deep. Still, the onshore gradients are
strong enough to push the low clouds and fog across the coastal
plains and even into the Santa Clarita Valley. The cutoff low
remains to the south of the region, allowing a narrow ridge to
nose in from the west and boost upper level heights slowly
through Wednesday morning. The rising heights may shrink the
marine layer depth, limiting the inland extent of low clouds tonight
into Wednesday morning. There is also a chance for patchy dense
fog across the coasts and valleys, especially north of Point
Conception. Early morning drizzle is possible each day due to
the changing upper level heights, that will lift or compress the
marine layer. The best chances for drizzle will be Thursday.

Daytime highs are expected to again increase today, as high
pressure builds. The greatest change will be for interior areas,
with warm conditions for the Antelope Valley, where highs will be
around 100 to 104 degrees. Minimal differences are expected for
the beaches and coastal valleys today. Temperatures are expected
to range from the upper 60s to mid 70s at the coasts and upper 70s
to upper 80s across the valleys. A slight cooling trend will
begin Wednesday everywhere, followed by a substantial drop in
temperatures on Thursday for inland areas. This trend will be
caused by an increase in onshore flow in conjunction with falling
heights, as the low pressure system crosses over the region
Thursday into Friday. Precipitable water will be minimal during
the passage of the low to the south of the region, thus no
significant convective potential is expected. However,
development of afternoon cumulus clouds over the mountains is
likely.

With onshore pressure gradients trending upward each day through
Wednesday, southwesterly winds will increase during the
afternoons/evenings across the Antelope Valley and foothills.
These winds are unlikely to reach advisory level. Late Thursday
night into Friday morning, the low pressure system will be east
of the region and sustaining strong upper level north-to-
northwesterly winds. The winds aloft will likely drive advisory
level level northwesterly winds across the I-5 cooridor, western
Antelope Valley, and the adjacent mountain ridgetops of Ventura
and Western Los Angeles Counties.

.LONG TERM (FRI-MON)...11/336 AM.

After the upper level low clears out of the region, a ridge will
build over the region. Friday night, the northerly pressure
gradient will shift to offshore, and easterly onshore gradients
decrease. Both the warm airmass aloft and the northerly offshore
flow and dampened marine influence will contribute to a warming
trend for Friday and Saturday.

Sunday and Monday, there is good agreement across the models that
a broad trough of low pressure will sweep over the area. The
easterly onshore pressure gradients will start to increase again,
and the offshore flow from the north is likely to subside. As a
result, temperatures will trend downward Sunday into early next
week.

Winds and fire weather will be the most impactful weather element
in the long term period. Thursday night into Friday morning,
strong northerly upper level winds driven by the exiting low
pressure, will likely create advisory level winds across the
across the I-5 cooridor and adjacent areas. Then Friday afternoon
through Monday, strong north to northwesterly winds will dominate
the western portions of the region. Winds will be very strong
over the coastal waters, and will impact wind prone locations
such as the I-5 Corridor, Antelope Valley, mountain ranges, and
the Santa Babara South Coast. These winds will be caused by
strong northerly pressure gradients that are forecast to peak
around 5 mb on Saturday. Humidities will drop over the region with
concerns for Sundowner Winds and impactful fire weather
conditions Friday night through Monday. The GFS currently shows
winds of 40-50 kts across the outer waters Friday night through
Sunday night.

This northerly flow will offer better clearing up north and most
marine layer clouds will be confined to LA and Ventura Counties.
-- End Changed Discussion --

&&

.AVIATION...11/1028Z.

At 0845Z at KLAX, the marine layer was 1500 ft deep. The top of
the inversion was at 4000 ft with a temperature of 24 C.

Good confidence in TAFs for KPMD and KWJF.

Low confidence in TAF for KPRB with a 40 percent chc of no cigs.

Moderate confidence in TAFs for KSBP and KSMX with a 30 percent
chc of 1/4SM FG conds 12Z-15Z. A 30 percent chc of VFR transition
delayed until 18Z.

Moderate confidence in remainder of TAFs. There is a 20 percent
chc of no clearing at sites with clearing fcst. Flight category
changes could be off +/- 2 hours.

KLAX...Moderate confidence in TAF. There is a 25 percent chc of
2SM BR OVC004 conds 12Z-15Z. There is a 30 percent chc of no
clearing. There is a 25 percent chc of 2SM BR OVC004 conds 12/09Z-
12/12Z No significant easterly wind component is expected.

KBUR...Moderate confidence in 00Z TAF.  There is a 25 percent chc of
1SM BR OVC002 conds 11Z-15Z. VFR conds may be delayed until 18Z.

&&

.MARINE...
-- Changed Discussion --
11/832 AM.

Good confidence in current forecast through Thursday afternoon
with Small Craft Advisories (SCA) not expected.

Moderate confidence the forecast for the nearshore waters along
the Central Coast. SCA conditions are likely (60 percent chance)
between Friday afternoon and Sunday. There is a chance (30 percent)
of GALE force winds Saturday afternoon through Sunday evening.

For the outer waters, SCA winds will likely (60 percent) develop
Thursday night over most of the area. GALE force winds are likely
(60 percent chance) Friday through Sunday. If GALES do not develop
there will be strong SCA conditions. An extended period of steep,
short period hazardous seas is likely between Friday and Sunday.

For the western Santa Barbara channel SCA winds and seas will
likely develop on Friday and continue through Sunday. There is a
slight chance (20 percent) of a period of GALE force winds
Saturday afternoon and evening.

For the inner waters including the eastern Santa Barbara Channel,
there is a low chance (25 percent) of SCA conditions. There is a
moderate chance of steep, short period hazardous seas Saturday
afternoon and night.
-- End Changed Discussion --

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...Schoenfeld/Rorke/Cohen
AVIATION...Rorke
MARINE...Rorke/RM
SYNOPSIS...MW/RS

weather.gov/losangeles

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