Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/28/23

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 829 PM PDT Sat May 27 2023

.SYNOPSIS...27/828 PM.

A strong onshore flow pattern will keep a persistent and deep
marine layer in place through next week. Night through morning
low clouds and fog will with limited afternoon clearing will
continue as well. Local drizzle is possible each morning across
coast and valleys. Temperatures will be cooler than average into
next week.

&&

.SHORT TERM (SAT-TUE)...27/827 PM.

Low clouds burned off better today across most areas, but are
beginning to redevelop this evening. Onshore pressure gradients
remain strong, with LAX-Daggett gradient peaking at +8 mb
this afternoon. Meanwhile, ACARS data showing the marine layer
depth around 3700 feet across the LA Basin this evening.
An upper level low pressure system off the coast of Oregon will
drop southward and become centered off the northern California
coast on Sunday. This will increase the cyclonic flow aloft across
Southwest California on Sunday and Monday, with gradually
lowering heights.

Little change in the marine layer depth and temperatures
expected on Sunday. There could be a return of patchy drizzle
on Sunday morning across the region (especially LA county), with
a better chance by Monday morning as the marine layer depth and
low level southerly flow increases. Looking for the low clouds and
fog to extend into the lower coastal slopes during the late night
and morning hours through Monday, with HREF sky cover ensembles
showing a slow burnoff of low clouds expected each afternoon.
High resolution models continue to show increasing instability
and some mid level moisture across the local mountains on Sunday
afternoon and again Monday afternoon. At this point, thinking
there will be some elevated cloud build-ups over the local
mountains (especially northern Ventura county mountains), but
the chance of thunderstorm activity is still only 10 percent
as moisture will remain somewhat limited.

*** From previous discussion ***

The marine inversion is expected to start deepening again Monday
and Tuesday as the upper low off the coast moves closer, cooling
the air aloft and pushing the marine layer back up. Could see a
return to patchy morning drizzle, especially over the lower coastal
slopes. Slower clearing and a slight cool down expected as well.

.LONG TERM (WED-SAT)...27/215 PM.

The upper low is expected to move onshore late Tuesday into
Wednesday, likely providing the best chance for morning drizzle
across coast and valleys. Temperatures will continue their slow
cooling trend, more so inland than at the coast. Following the
upper low passage there will be a slow recovery of heights aloft
resulting in a very minor warm up through the end of the week.
Onshore flow remains seasonably strong, 8-10mb to the east each
day so at the very least we`re looking at a later than usual
clearing of the marine layer and afternoon temps that are still
3-6 degrees below normal through Saturday. Model clusters
continue to support this idea, with virtually all members showing
below normal 500mb heights into next weekend.

&&

.AVIATION...27/2321Z.

At 2215Z, the marine inversion at KLAX was based at 3300 feet.
The top of the inversion was 5500 feet with a temperature of
16 degrees Celsius.

Overall, moderate confidence in 00Z TAF package. High confidence
in return of MVFR CIGs to all coastal and valley sites overnight,
but low confidence in timing of return (could be +/- 4 hours of
current forecasts).

KLAX...Moderate confidence in 00Z TAF. Timing of return of MVFR
CIGs could be +/- 4 hours of current 07Z forecast. No significant
easterly wind component is expected.

KBUR...Moderate confidence in 00Z TAF. Timing of return of MVFR
CIGs could be +/- 4 hours of current 09Z forecast.

&&

.MARINE...27/150 PM.

No changes to the marine forecast in the afternoon issuance.

For the Outer Waters, high confidence in current forecast. Tonight
through Wednesday, winds and seas are expected to remain below
Small Craft Advisory (SCA) levels.

For the Inner Waters north of Point Sal and south of Point
Concpetion, high confidence in current forecast. Tonight through
Wednesday, winds and seas will remain below SCA levels.

&&

.BEACHES...27/150 PM.

Long-period south swell originating from the Southern Hemisphere
will move into the coastal waters between Saturday night and
Tuesday. Strong rip currents and elevated surf of 3 to 5 feet will
be possible over the Memorial Day holiday weekend. There will be
the potential for hazardous rip currents and a Beach Hazards
Statement may be needed later this weekend.

&&

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

&&

$$

PUBLIC...Gomberg/MW
AVIATION...RAT
MARINE...Sweet/RAT
BEACHES...Sweet/RAT
SYNOPSIS...MW

weather.gov/losangeles

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