Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 031651
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
951 AM PDT Mon Aug 3 2020

.SYNOPSIS...03/327 AM.

There will not be much change in temperatures today from
yesterday. A cooling trend will start Tuesday and continue through
mid week before a warming trend that will start at the end of the
week. The night through morning low cloud regime will continue and
expand.

&&

.SHORT TERM (TDY-WED)...03/949 AM.

Marine layer stratus covers the coastal waters and adjacent
beaches south of Pt Conception this morning but deepened a little
overnight so not quite as much dense fog as yesterday. Agree with
earlier forecast that the transition zone between the beaches and
valleys will be a tricky temperature forecast but aside from that
today will feel a lot like yesterday. Probably the biggest
difference will be the return of Sundowners to southwestern SB
County later today and this evening and a wind advisory has
already been posted for that.

***From Previous Discussion***

A trof moves into the state on Tuesday and expands on Wednesday.
Hgts fall, the marine layer will lift into the vlys and the
onshore flow will increase. All of these will combine to drop max
temps 4 to 8 degrees on Tue and another 3 to 6 degrees on Wed. Max
temps on Wed will be 4 to 8 degrees blo normal.

The increasing west to east flow will bring near advisory level
winds to the Antelope Vly and foothills each afternoon.

.LONG TERM (THU-SUN)...03/327 AM.

Low excitement levels for the extended period as the marine layer
seems to have lost all of its calenders and still thinks its June.
Broad west coast troffing will continue through Sunday, although
it will weaken and hgts will rise starting Friday. There will be
strong onshore flow each day esp from the west to the east.

The night through morning low cloud pattern will continue through
the week and into the weekend. The strong onshore flow will make
for slow clear and will keep some beaches cloudy all through the
afternoon. The marine cloud coverage will lessen over the vlys
over the weekend and hgts increase.

Temps Thursday will be similar to Wednesday perhaps a little
cooler over LA county. As hgts rise max temps away from the coast
will warm a little each day Fri-Sun.

There will likely be some gusty westerly winds during the afternoons
across the Antelope Valley and surrounding mountain areas. The
afternoon seabreezes will also be a little stronger than normal,
but otherwise not expecting any winds of note.

&&

.AVIATION...03/1208Z.

At 12Z at KLAX...the marine layer was around 1500 ft deep. The top
of the inversion was around 3500 ft with a temp of 28 degrees C.

Low clouds were fairly widespread in coastal areas south of Pt.
Conception, and have pushed into the lower valleys of VTU County.
Conds were mostly IFR to LIFR, except locally VLIFR across VTU
County. North of Pt. Conception, low clouds were patchy, mainly
affecting southern portions of the Central Coast and the Santa
Ynez Valley. Conds were mostly LIFR to VLIFR where there were
cigs. Expect skies to clear by mid morning, except possibly late
morning near the beaches.

Gusty west winds will affect the Antelope Valley this afternoon
and evening. Gusty NW winds will affect the I-5 Corridor through
late tonight and western portions of the Santa Ynez Range and
the adjacent south coast of SBA County tonight.

Expect widespread low clouds in coastal areas tonight, with the
exception of the south coast of SBA County due to areas of gusty
NW to N winds. N-S gradients should keep clouds out of the San
Fernando Valley.

KLAX...Moderate confidence in the 12Z TAF. There is a 20-30%
chance that cigs could linger to 16Z. There is a 20-30% chance
that cigs will arrive as early as 06Z this evening.

KBUR...High confidence in the current TAF. There is a 20% chance
of LIFR to IFR cig after 10Z tonight.

&&

.MARINE...03/912 AM.

For the morning update...expanded the Gale Warning for late this
afternoon through tonight into zone PZZ676, otherwise no other
changes.

From last discussion...

Across the outer waters...Gale Force winds are expected to
develop from north to south in the northern two zones (PZZ670,673)
today, preceded by Small Craft Advisory level winds. Winds will
be strongest across western portions of the zones. Winds should
drop below Gale Force late tonight, then SCA level winds are
likely from late tonight thru late Wed night. There is a 40% chance
of SCA level winds Thu thru Fri. Across the southern zone (PZZ676),
SCA level winds are expected to develop today, strongest NW of
San Nicolas Island, then SCA level winds will continue thru late
Wed night. There is a 50% chance of SCA level winds Thu thru Fri.

Across the inner waters north of Pt. Sal, winds will increase to
SCA levels this afternoon and continue thru late tonight. There
will be a lull in the winds Tue morning, but SCA level winds are
expected Tue afternoon thru late Tue night. SCA level winds are
likely Wed afternoon and evening, There is a 30% chance of SCA
level winds Thu afternoon and evening.

Across the inner waters south of Pt. Conception...winds across
the western Santa Barbara Channel will reach SCA levels this
afternoon thru late tonight, and again Tue afternoon thru late
Tue night. SCA level winds are likely across western portions of
the SBA Channel Wed afternoon and evening, then there is a 30-40%
chance of SCA level winds there during the afternoon and evening
hours Thu and Fri. SCA conds are not expected across the
remainder of the inner waters south of Pt. Conception.

Patchy fog, locally dense with visibility down to one mile or
less, will affect the waters this morning.

&&

.FIRE WEATHER...03/950 AM.

The strong upper level ridge of high pressure that brough the hot
temperatures over the weekend is beginning to weaken, bringing
increased onshore flow and marine layer influence to coastal and
coastal valley areas of Los Angeles and Ventura counties. However,
a northerly wind influence is bringing drier air into much of
Santa Barbara and San Luis Obispo counties away from the coast.
Above the marine layer, a hot and very dry air mass will linger
one more day across all interior areas, with temperatures ranging
between 95 and 105 degrees and humidities ranging between 5 and 15
percent. The hot, dry, and unstable conditions combined with dry
fuels will lead to a coninued risk of deep vertical plume
development with existing and new fire ignitions across the
interior today. West to north wind gusts between 20 and 40 mph
will continue through tonight, strongest over the Antelope Valley
and Los Angeles county mountains each afternoon, and over the I-5
Corridor and southern Santa Barbara County during the late
afternoon and nighttime hours. The combination of hot
temperatures, very low humidities, and locally gusty winds will
bring elevated to brief critical fire weather conditions today
across the mountains, foothills, interior valleys, and deserts.

Sundowner winds are expected across the western portions of the
Santa Barbara south coast and foothills during the late afternoon
through nighttime hours today through Wednesday, where wind gusts
of 30 to 45 mph can be expected (strongest near Gaviota).
Humidities will generally range between 15 and 35 percent with
temperatures rising to the lower 90s in warmest locations with
todays sundowner wind event. Humidities are expected to be
slightly higher with the Tuesday and Wednesday sundowner winds as
temperatures begin to cool somewhat. Widespread cooling and an
increase in humidity is expected for Tuesday through Friday,
including improved overnight recovery. However, the increased
onshore flow will continue to bring gusty onshore winds to the
mountains and Antelope Valley through the period.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect from 3 PM this afternoon to 3 AM PDT
      Tuesday for zones 39-52. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3
      AM PDT Wednesday for zones 645-650. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Tuesday for zone 670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 PM PDT this afternoon
      for zones 673-676. (See LAXMWWLOX).
     Gale Warning in effect from 3 PM this afternoon to 3 AM PDT
      Tuesday for zones 673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (WED-SUN).

Gusty winds are possible through the Highway 14 Corridor and the
Antelope Valley each afternoon and evening. The gusty winds will
create elevated fire danger.

&&

$$

PUBLIC...MW/Rorke
AVIATION...DB
MARINE...Sweet/DB
FIRE...Gomberg
SYNOPSIS...30

weather.gov/losangeles



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