747
FXUS66 KLOX 021157
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
457 AM PDT Thu May 2 2024

.SYNOPSIS...02/455 AM.

A dry weather pattern will continue through Saturday as the region
remains between high pressure aloft to the west and an exiting
trough to the east. Warming will continue to take shape across the
northern and interior portions of the area today, while a
persistent marine layer will moderate the warming across the South
Coast of California. An unseasonably cold storm system will brush
the area to the north this weekend and bring cooler temperatures,
gusty winds, and a chance for light precipitation Saturday into
Sunday. A warming and drying trend will develop for the work week
next week.

&&

.SHORT TERM (TDY-SAT)...02/455 AM.

Zonal flow remains aloft over the region early this morning as the
area sits between a broad upper-level trough to the east and an
upper-level ridge over the eastern Pacific Ocean. A fairly complex
surface pattern exists across the area as ridging to the west has
created a weak offshore flow pattern across the area. Offshore
flow is present across the Central Coast of California this
morning, but a persistent eddy circulation remains intact across
the southern California bight. With the offshore flow pattern
being too weak, it is unlikely for the eddy to get dislodged from
the bight. As a result, a persistent marine intrusion will remain
wedged in place for today across the South Coast of California.
Low clouds and fog have spread into the the Los Angeles County
coastal plain and into the San Gabriel Valley. Clouds are starting
to push north along the Ventura County coast and the south coast
of Santa Barbara County. Clouds are expected to push into most
coastal and valley areas south of Point Conception this morning,
but there is a moderate chance that the eddy circulation could
pull too far offshore and result into some clearing skies to start
the day.

A warming trend should develop today as offshore flow should
assert some influence with the compressional heating, but the
warming trend could be more muted or even closer to persistence
along the South Coast of California due to the low cloud field
already present across the area. The forecast preserves a warming
trend continuing into today while moderating the warming along
the Los Angeles, Ventura, and southern Santa Barbara Counties.
There is a moderate chance that clouds could hug the beaches and
struggle to clear off the southern coastal areas this afternoon,
but more confidence exists in the offshore push being able to
clear off the clouds just off the coast.

A wind advisory was cancelled early this morning as northerly
winds weakened with the northerly surface gradient relaxing some,
but there is another chance of gusty northerly winds through the
Interstate 5 Corridor tonight as the surface pressure gradient
tightens again. There is a moderate chance that a wind advisory
could be issued for the same areas tonight and into Friday
morning as NAM-WRF boundary layer winds increase to 25 knots.

With the ridge aloft and offshore flow weakening later today, the
marine layer cloud field should become a bit more entrenched
tonight and into Friday morning. Ridging aloft should tighten the
marine inversion some and possibly inhibit clearing on Friday at
the beaches. A return of low clouds and fog should occur along the
Central Coast, but there is a moderate chance that the low cloud
forecast could be a little too expansive along the Central Coast
for late tonight and into Friday morning.

By Friday night, cyclonic flow will start to develop and a
deepening marine layer should be expected as onshore flow
strengthens. Marine layer induced low clouds and fog should be
fairly aggressive on Friday night and Saturday as low clouds and
fog will likely push into the coastal slopes of the mountains.
Much cooler temperatures will start to spread into areas north of
Point Conception on Saturday as an unseasonably cold upper-level
trough digs into northern California. A cold frontal boundary will
drop south into the region late Saturday and bring an increase in
chances for precipitation on Saturday night.

.LONG TERM (SUN-WED)...02/455 AM.

The frontal boundary will continue to move south and east over
the area into Sunday while weakening some. The highest chance for
precipitation will be for areas north of Point Conception, along
the northern slopes of the mountains, and into the San Gabriel
Valley between Saturday night and Sunday. EPS, GEFS, and CMC
ensemble members buy into this idea emphasizing these areas being
wetter. Southern Santa Barbara County, Ventura County, and western
Los Angeles County could end up being in a rain shadow effect as
downsloping occurs from the Transverse Ranges. PoPs break away
from NBM values between Saturday night and into Sunday, and go
higher than the previous forecast for the wetter areas. Likely
PoPs may be needed by future shifts if the pattern continues for
areas north of Point Conception, along the northern slopes of the
mountains, and into the San Gabriel Valley. Almost all solutions
of the EPS suggest rain for terminals north of Point Conception,
KSDB, KEMT, and KPOC.

Temperatures will be quite cool for Sunday across the area. Record
cold high temperatures could be tied in some areas as a cold
pattern for May sets up. Temperatures go colder than NBM values
for Sunday.

Gusty winds could end being the main story with this system. EPS
members produce a broad period of gusty winds between Sunday and
Monday morning. Gusty west to northwest will likely develop on
Sunday across most areas, and a wide swath of wind advisories
might be needed for Sunday afternoon and evening. Gusty northwest
to north are likely to linger through the Interstate 5 Corridor
and into southern Santa Barbara County for Sunday night and into
Monday morning.

A warming and drying trend should develop for the work week next
week as forecast ensemble advertised a consistent warming trend in
the temperature means.

&&

.AVIATION...01/2336Z.

At 2300Z at KLAX, the marine layer was 1900 ft deep with an
inversion top at 4300 ft with a temperature of 17 C.

Low to moderate confidence in coastal TAF sites and KBUR and KVNY,
with high confidence elsewhere. Timing of flight cat changes
could be off by +/- 2 hours, and cigs may develop one category
lower than forecast for coastal sites in Ventura and L.A.
counties. There is a 30% chance of no cigs developing for KSBA,
KBUR, and KVNY, and a 30-40% chance of IFR cigs overnight for
KSMX.

KLAX...Low to moderate confidence in the 00Z TAF. Timing of
flight cat changes could be off by +/- 2 hours, and there is a 20%
chance of cigs as low as BKN008. High confidence in any east wind
component remaining less than 6 kt.

KBUR...Low to moderate confidence in the 00Z TAF. Timing of
flight cat changes may be off by +/- 2 hours, with a 30% chance of
no cigs developing tonight, and a 30% chance of IFR cigs
developing overnight.

&&

.MARINE...01/1036 PM.

For the outer waters, there is currently a lull in the Gale Force
winds, but expecting these winds to strengthen again tomorrow
afternoon/evening. At least SCA wind are expected much of the
time through Sunday, and Sunday afternoon and night there is a 40%
chance of gales returning. SCA level seas are expected through
Friday night followed by a 40-50% chance of SCA seas on Sunday and
Monday.

For the inner waters N of Pt. Sal, SCA level winds are likely to
continue through tonight with a brief lull tomorrow morning. SCA
level winds should return during the afternoon/evening Thursday
and Friday (25% chance of brief gales during these times), and a
40% of SCA winds Saturday afternoon/evening. SCA winds are then
likely (70% chance) Sunday and Monday. Current SCA level seas will
subside Thursday night, followed by a 20% chance of returning
Sunday and Monday.

For the Santa Barbara Channel, SCA level winds will affect the
western portions of the the channel this afternoon and evening,
with a 20% chance of reaching the central/eastern portions.
Thursday onward, SCA level winds are generally expected to only
impact the extreme western portions of the channel, until
Saturday afternoon. Saturday afternoon through Sunday night there
is a 40-50% chance of widespread NW SCA winds for the entire
channel, with the potential (20% chance) for gales on Sunday.

For the southern inner waters, SCA winds are expected early
tonight over far western portions of the Santa Barbara Channel,
and again Friday evening (20% chance). Otherwise, conditions are
expected to remain below SCA levels until Saturday afternoon.
Saturday afternoon through Sunday there is a 40-50% chance of
widespread NW SCA winds for all the inner waters, with the
potential (20% chance) for gales on Sunday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Friday for zone
      645. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 3
      AM PDT Friday for zone 650. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Friday for zones
      670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Hall
AVIATION...Smith
MARINE...Phillips/Schoenfeld
SYNOPSIS...Hall

weather.gov/losangeles

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