Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/23/23

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 812 PM PDT Sat Apr 22 2023

.SYNOPSIS...22/810 PM.

A cooling trend is on the way for Sunday and Monday with
increasing onshore flow and an increase of night through morning
low clouds and fog. A warming trend is forecast for the middle and
end of next week, especially for interior areas.

&&

.SHORT TERM (SAT-TUE)...22/809 PM.

Another very warm day across inland areas today, with highs
in the mid 80s to lower 90s. Slight cooling along some immediate
coastal areas due to earlier arrival of sea breeze. As upper level
ridge of high pressure continues to break down tonight into
Sunday, pressure gradients will continue to trend onshore to the
east. Current satellite imagery showing low clouds and fog
returning to portions of the Central Coast this evening which will
become more widespread overnight. In addition, high resolution
models and HREF guidance indicate that low clouds and fog
will become likely late tonight into Sunday morning across
portions of the LA/Ventura county coastal areas. ACARS data
showing a very shallow marine layer depth in place this evening
(around 500 feet). As a result, there is the potential for
patchy dense fog to form later tonight into Sunday morning.

The other short term concern is gusty northerly winds across
southern Santa Barbara county. The strongest winds have been
focused across the western portions of the Santa Barbara
south coast and Santa Ynez mountains where wind advisories in
effect until 6 am Sunday due to wind gusts of 35 to 50 mph.
The strongest winds will be focused near Gaviota and Refugio.
Gusty northerly winds will also expand to the eastern portions of
the Santa Ynez range and I-5 corridor, but wind advisories are
not expected to occur tonight. Most areas will see a cooling
trend on Sunday, especially coastal areas due to the increased
onshore flow and marine layer influence.

*** From previous discussion ***

Onshore flow expected to peak Monday afternoon so additional
cooling and marine layer coverage Monday with slower clearing.
Forecast soundings indicate the inversion base will rise to at
least 1500 feet Monday, meaning there`s good chance that clouds
will move into at least some of the coastal valleys. Northerly
flow expected to continue through Monday in southern Santa Barbara
County which will hinder clouds from moving in there but the
eastern portion from Santa Barbara east could eventually see some
morning low clouds.

A weak trough passage to the north will reverse gradient trends
Tuesday leading to some warming and earlier clearing marine layer.

.LONG TERM (WED-SAT)...22/1147 AM.

The longer range forecast remains basically unchanged. Ensembles
continue to support the building ridge idea in the deterministic
models so confidence remains high on a warming trend, especially
mountains and deserts. Onshore flow is weakest on Wednesday which
should also correspond to the warmest day for coast and valleys
before onshore flow increases each day through the end of the
week and marine layer becomes more robust. By Friday afternoon
onshore flow is expected to be at least 8mb so expect to see
increasing breezes across the Antelope Valley.

&&

.AVIATION...23/0040Z.

At 2350Z at KLAX, the marine layer was 500 ft deep. The top of
the inversion was at 1900 ft with a temperature of 22 C.

Moderate confidence in Ventura and L.A. coastal TAFs, KSMX, and
KSBP. High confidence for all other TAFs. There is a 20% chance of
conds remaining VFR at KLGB and KSMX, and a 30% chance of VLIFR
conds at KSMX. There is a 30% chance of IFR conds at KSBP, KOXR,
KCMA, KLAX, and KSMO after 10Z-17Z.

KLAX...Moderate confidence in TAF. High confidence in VFR
conditions through this evening. There is a 30% chance of bkn006
conds 10-17Z. There is a 20% chance of the easterly wind
component reaching 8 kts briefly from 09Z-15Z.

KBUR...High confidence in TAF.

&&

.MARINE...22/156 PM.

For the Outer Waters, moderate to high confidence in current
forecast. Small Craft Advisory (SCA) level winds will continue
into early this afternoon, then will increase to Gale force late
this afternoon and continue through Sunday night. So, a GALE
WARNING remains in effect from this afternoon through Sunday
night. There is a 30-50% chance that the Gale force winds may
continue through Monday. Even without gales, high confidence in
SCA level winds and seas Monday and Tuesday. For Wednesday, high
confidence in winds and seas dropping below SCA levels.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. Today through Tuesday, high
confidence in combination of SCA level winds and seas. There is
a 30-40% chance of Gale force winds Sunday and Sunday night. For
Wednesday, high confidence in winds and seas dropping below SCA
levels.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. For the western half of the Santa
Barbara Channel, high confidence in SCA level winds from this
afternoon through Sunday afternoon with a 50-70% chance of the
SCA level winds continuing Sunday night through Tuesday.
Otherwise, high confidence in winds and seas remaining below SCA
levels today through Wednesday for the remainder of the southern
Inner Waters.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 6 AM PDT Sunday for zones
      349-351. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 9 AM PDT Sunday for zone
      645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 PM PDT Sunday for zone
      650. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Monday for zones
      670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Gomberg/MW
AVIATION...Lund
MARINE...RAT/Schoenfeld
SYNOPSIS...Gomberg

weather.gov/losangeles

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