Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/27/23

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 857 PM PDT Fri May 26 2023

.SYNOPSIS...26/855 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. Drizzle or very light rain is possible each
morning across coast and valleys. Temperatures will be cooler than
average into next week.

&&

.SHORT TERM (FRI-MON)...26/853 PM.

An upper level trough moving through interior California and the
Great Basin has created a strong onshore flow pattern along with
a deepening marine layer today. The LAX-Daggett pressure gradient
has peaked at +9 mb late this afternoon, while ACARS data shows
the marine layer depth remains over 4000 feet across the LA Basin.
Current satellite imagery showing extensive low clouds lingering
for areas south of Point Concpetion, extending into the lower
coastal slopes. The deep marine layer pattern will continue to
bring the potential for patchy drizzle late tonight into Saturday
morning, especially LA county.

On Saturday, a weak ridge will replace the trough but impacts for
most will be minimal. With warmer air moving in aloft the marine
inversion will likely lower a bit on Saturday. This will reduce
the amount of moist ocean air getting into the far interior areas
like the Antelope Valley, consequently boosting afternoon
temperatures back into the low to mid 80s. Most everywhere else
probably not much change from the last several days, with the May
Gray pattern remaining in place. There will be slow clearing
this weekend at best with highs still mostly in the 60s.

*** From previous discussion ***

Given the lowering and strengthening inversion a case could be
made that the low clouds will have an even tougher time clearing.
In any case, May Gray conditions are expected to continue through
the extended holiday weekend for coast/valleys with much below
normal temps. The main exception to this will be the Central
Coast, which, due to the orientation of the coastline and slightly
shallower marine layer skies are expected to clear each
afternoon.

For the mountains on Sunday there is some increasing instability
as the next trough approaches from the northwest. Forecast
soundings are much less impressive than last weekend but ensembles
do show increasing moisture and afternoon cloud cover Sunday. At
this point chances are too low to include in the forecast, still
10% or less, but something to keep an eye on with the best chances
over the far northern Ventura mountains.

.LONG TERM (TUE-FRI)...26/202 PM.

Next week`s forecast looks much the same as this week. Forecast
models, while not in the best of agreement, all basically indicate
this same pattern lasting through next week as a series of weak
upper lows move through the West Coast. Model clusters are in
almost unanimous agreement that height anomalies will be around
100m below normal. Add in an expected onshore gradient of 9-10mb
each day and the unavoidable conclusion in a continued May
Gray/June gloom pattern with high temps of 5-10 degrees below
normal. Consensus models indicate a less than 10 percent chance of
reaching 70 in downtown LA most days through next week (normal is
74), with only next Friday up to 30% of reaching 70. This is all
consistent with CPC`s forecast of below normal temperatures, which
also extends through early the following week.

&&

.AVIATION...27/0004Z.

At 2345Z at KLAX, the marine layer was 4200 ft deep. The top of
the inversion was at 5000 feet with a temperature of 11 C.

Moderate confidence in the cst/vly TAFs. SCT-BKN030-040 conditions
will likely continue through the evening hours,, wide more
widespread cigs returning overnight into Saturday
morning.Forecasting most sites to lower to MVFR category overnight
into Saturday morning, however there is a 20% chance of cigs
lingering in VFR category. Slow to no clearing across coastal
TAFs on Saturday afternoon.

KLAX...Moderate confidence in 00Z TAF. VFR cigs likely to persist
at KLAX through the evening, with a few hours of SCT conditions
likely between 04z-07z. On Saturday, there is a 30 percent chance
of cigs dropping to MVFR category after 16z, and a 20 percent
chance of clearing by late afternoon.

KBUR...Moderate confidence in 00Z TAF. There is a 50 percent chc
of SCT conds 04Z-10Z. Otherwise MVFR-VFR cigs expected to persist
through at least Saturday morning.

&&

.MARINE...26/811 PM.

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. There is the possibility of
some local gusts around 25 knots around the Point Conception area
this weekend.

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

For the Inner Waters south of Point Concpetion, high confidence
in current forecast. Across the western half of the Santa Barbara
Channel, there may be some local gusts to 25 knots this weekend
during the afternoon and evening hours. Otherwise, winds and seas
will remain below SCA levels through Wednesday.

&&

.BEACHES...26/811 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 may
affect area beaches over the Memorial Day holiday weekend. As the
swells are marginal in the latest swell guidance, a Beach Hazards
Statement may be needed to highlight the increased potential for
dangerous rip currents.

&&

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

&&

$$

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

weather.gov/losangeles

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