Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 06/05/21

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 812 PM PDT Fri Jun 4 2021

.SYNOPSIS...04/654 PM.

Increasing onshore flow will bring a cooling trend to inland areas
through early next week and will keep persistent low clouds and
fog in place with much cooler temperatures along the coast.
Afternoon temperatures will begin to warm again beginning mid
week.

&&

.SHORT TERM (FRI-MON)...04/725 PM.

Upper level ridge of high pressure over the region today will
gradually weaken through the weekend. Another day of strong
onshore flow caused the June Gloom pattern to persist along the
coast. The LAX-Daggett gradient peaked at +9 mb this afternoon,
while LAX-Bakersfield gradient peaked at +6 mb. 00Z Vandenberg
sounding and ACARS data over the LA basin currently showing the
marine layer depth around 1300 feet. With heights gradually
lowering and the presence of a weak eddy circulation, expecting
marine layer depth to gradually increase on Saturday, with low
clouds filling in across most coastal/valley areas by Saturday
morning. Current satellite imagery showing low clouds and fog
beginning to advance inland across the coastal plain this evening.

Onshore flow is expected to be even slightly stronger on Saturday
and Sunday afternoons, with LAX-Daggett gradient likely peaking
at around +10 mb and LAX-Bakersfield gradient at +7 mb, which
would be exceeding the 97th percentile for strong onshore
gradients this time of year. The stronger onshore flow and deeper
marine layer is expected to bring cooling to the entire forecast
area. The interior valleys of San Luis Obispo County will feel the
most significant cooling from today`s readings due to an expected
southwest wind direction which will bring greater marine layer
influence. ONshore winds will likely further strengthen through
the weekend, with gusts generally in the 25 to 40 mph range across
interior valleys, mountains, and deserts each afternoon and
evening. Isolated gusts as high as 50 mph can be expected in the
foothills of the Antelope Valley during the afternoon and evening
hours on both Saturday and Sunday. As a result, a wind advisory
may need to be considered at some point for the Antelope Valley
this weekend. The gusty onshore winds combined with relatively
low humidities, and unseasonably dry fuels will lead to a
continuation of elevated fire weather conditions across the
interior through the weekend.

*** From previous discussion ***

Monday we`ll likely see a rapid deepening of the marine layer as
the upper low finally swings through. Model soundings suggest at
least a 4000` marine layer depth and with that possibly some
drizzle for coast/valleys south of Pt Conception. Probably not
much clearing for coastal areas and possibly valleys as well.
Temps will likely be the coolest of the week with most coastal
valleys in the lower 70s at best and the Antelope Valley only low
to mid 80s.

.LONG TERM (TUE-FRI)...04/205 PM.

After the upper low moves through onshore flow is expected to
weaken and possibly turn lightly offshore by Thursday if the ECMWF
is correct. However, there`s a fair amount of uncertainty with
temperatures as some model solutions keep a rather deep trough
along the West Coast while others, particularly the ECMWF, are
much weaker and warmer. So there`s a larger than usual spread of
possible temperatures from mid to late week, but either way temps
will be warming up with a very good chance of above normal temps
Thursday and especially Friday.

&&

.AVIATION...05/0026Z.

At 0010z at KLAX... The inversion was around 1300 feet. The top
of the inversion was around 4700 feet with a temperature of about
24 degrees Celsius.

Overall... Moderate to high confidence in the current TAFs.
IFR/MVFR CIGs near immediate coastal areas as of 0010z, will
spread inland quickly across most coastal/valley TAF sites
through this evening, with potential for LIFR cigs to develop
overnight, especially at KSBP, KSMX, KSBA, AND KOXR. KPRB, KPMD,
and KWJF will remain VFR throughout the forecast period, with
gusty onshore winds during the afternoon and evening hours.

KLAX... High confidence in the current TAF. IFR/MVFR conditions
will likely return around 03z, with arrival time likely +/- 1 hour
of 03z. There is a ten percent chance of east winds greater than
8 kts during the 13z- 17z period.

KBUR... High confidence in the current TAF. IFR/MVFR conditions
will likely return by 07z, with arrival time likely +/- 1 hour of
07z.

&&

.MARINE...04/809 PM.

Patchy fog, locally dense with visibility under one mile, will
continue into next week. The poorest visibility and most widely
spread conditions will occur in the overnight and morning hours.

Across the outer waters... Winds will be Small Craft Advisory
(SCA) level near Point Conception and northward through Sunday,
though they may drop below SCA level during morning hours. There
will be SCA level winds across all of the outer waters
Monday through Wednesday. Otherwise and elsewhere, conditions
will be below SCA levels.

Across the inner waters north of Point Sal... Winds will increase
to SCA level Monday through Wednesday during the afternoon and
evening hours. Otherwise, conditions will remain below SCA
levels.

Across the inner waters south of Point Conception... Winds through
the Santa Barbara Channel and down to Point Mugu will increase to
SCA level Monday and Tuesday the afternoon and evening hours. The
winds will be SCA level across all of the inner waters on
Wednesday. Otherwise and elsewhere, conditions will be below SCA
levels.

&&

.BEACHES...04/810 PM.

High surf and dangerous rip currents along the southwest-facing
beaches of Los Angeles and Ventura counties will diminish this
evening but will remain elevated into Saturday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Monday for zone
      670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Sunday for zone
      673. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (MON-FRI).

No significant hazards expected.

&&

$$

PUBLIC...Gomberg/MW
AVIATION...Gomberg
MARINE...Kj
BEACHES...Kj
SYNOPSIS...Kj

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