417
FXUS66 KLOX 060649
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1149 PM PDT Wed Jun 5 2024

.SYNOPSIS...05/735 PM.

High pressure over the region will continue above normal
temperatures through Thursday, most pronounced away from the
coast. The marine layer will continue to bring some night through
morning low clouds to the coastal and valley areas. While very
warm temperatures are expected over the interior through Saturday,
closer to the coast, highs will be moderated by the marine layer
and moderate to strong onshore flow.

&&

.SHORT TERM (WED-SAT)...05/1022 PM.

***UPDATE***

Marine layer clouds made an early return to the coasts this
evening under a strong inversion. With heights around 590 to 592
dam, a marine layer depth around 1800 ft and onshore flow with a
6 mb LAX to DAG gradient tonight, expecting low clouds and patchy
fog to push through the coastal plains and into the valleys
overnight. There is some uncertainty if dense fog will develop
near the coasts, may need to add dense fog over the coastal
waters for tonight into Thursday morning.

Thursday morning, the upper level pattern shows high pressure
slowly decreasing as the center of the ridge shifts eastward which
will start deepening the marine layer. Skies will struggle to
clear at the coasts through the day, especially for west-facing
beaches as the afternoon LAX-DAG onshore gradient is expected to
trend stronger peaking near 8-9 mb. Clouds and patchy fog will
push deeper into the valleys Thursday night, and not seeing an end
to marine layer clouds as gradients trend stronger and heights
continue to fall. The current forecast looks on track, with only
minor changes made to the extent of marine layer clouds and patchy
fog.

.SHORT TERM (WED-SAT)...05/133 PM.

Overall for the short term, 12Z models in good synoptic agreement
through the period. At upper levels, ridge will remain over the
desert Southwest through Thursday then will shift eastward Friday
and Saturday as a trough develops along the West Coast. Near the
surface, onshore flow will gradually strengthen through the
period.

Forecast-wise for the immediate short term, main issue is heat.
With upper ridge remaining dominant feature through Thursday,
inland heat will continue. Looking at both deterministic and
ensemble stuff, heat will continue through Thursday across
interior sections with temperatures actually threatening records
across the Antelope Valley. So will keep EXCESSIVE HEAT WARNING in
effect for the Antelope Valley and HEAT ADVISORIES in effect for
interior San Luis Obispo county, the Cuyama Valley and the western
range of the San Gabriel Mountains. For areas west of the
mountains, a continued marine influence and moderate to strong
onshore gradients will keep things cooler. For Friday and
Saturday, all areas will experience some slight cooling on Friday
and a bit more pronounced cooling on Saturday.

Otherwise, no major issues are expected through Saturday. Will
expect the marine inversion to gradually deepen each day with
better inland penetration each night/morning. Dissipation of
stratus each day should be good for all areas but the immediate
coast where clouds could remain stubborn each afternoon. Also, 12Z
models came in much drier at mid-levels on Thursday, so have
knocked down POPs to below mentionable levels for the mountains.
As for winds, the moderate to strong onshore gradients will
generate gusty southwesterly winds across interior sections,
including the Antelope Valley, but any advisory-level winds should
remain localized.

.LONG TERM (SUN-WED)...05/133 PM.

For the extended, 12Z models continue to exhibit decent synoptic
agreement. At upper levels, trough will linger along the West
Coast through Sunday then will slowly drift southwestward early
next week (well offshore) as a ridge builds once again over the
desert Southwest. Near the surface, moderate to strong onshore
gradients are forecast to continue.

Forecast-wise, no significant issues are anticipated through the
period. Main "concern" will be the continued presence of the
marine layer stratus. Inversion likely to be deepest on Sunday
then will shrink slightly early next week. So, low clouds and fog
will likely push into the coastal valleys each night with good
dissipation each afternoon. Other than the stratus, skies should
remain mostly clear through the middle of next week. As for
temperatures, Sunday will likely be the coolest day with a slight
warming trend for most areas Monday through Wednesday. The onshore
gradients will continue to generate gusty southwesterly winds each
afternoon across interior sections.

&&

.AVIATION...06/0627Z.

At 0505Z at KLAX, the marine layer was 1700 ft deep. The top of
the inversion was at 3800 ft with a temperature of 27 Celsius.

Fairly good confidence in TAFs. There is a 30 percent chc of LIFR
conds at sites with only IFR conds fcst. Flight Cat transition
timing my be off by +/- 1 hour.

KLAX...Fairly good confidence in TAF. There is a 30 percent chc of
3SM OVC004 conds 11Z-15Z. There is a 20 percent chc that cigs will
remain blo OVC010 through the period. High confidence that any
east wind component will remain blo 7 kt.

KBUR...Fairly good confidence in TAF. There is a 30 percent chc of
2SM BR conds 11Z-15Z. VFR transition could occur as late as 1930Z.

&&

.MARINE...05/733 PM.

Small Craft Advisory (SCA) winds and seas have ended for the outer
waters off the Central Coast. Otherwise, southeast to southwest
winds are expected for much of the waters through Thursday. Winds
will peak around 15 knots in the afternoon and in the morning
between the islands and through any channels. There is a 30%
chance of SCA level winds late Sat thru Sun, especially off the
Central Coast.

Reduced visibilities are expected each morning through at least
the weekend, possibly dense each morning and below one mile from
Santa Barbara to the Central Coast.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory in effect until 8 PM PDT Thursday for zones
      38-343-344-379. (See LAXNPWLOX).
     Excessive Heat Warning in effect until 8 PM PDT Thursday for
      zones 381>383. (See LAXNPWLOX).
PZ...NONE.

&&

$$

PUBLIC...Thompson/Phillips
AVIATION...Rorke
MARINE...Kittell/Smith
SYNOPSIS...Smith

weather.gov/losangeles

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