LA Area Forecast Discussion

537
FXUS66 KLOX 131627
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
927 AM PDT Tue May 13 2025

.SYNOPSIS...13/917 AM.

Another cool and windy day is on tap for today as an upper level
trough exits the region. Then, a gradual warm up is expected with
generally lighter onshore winds for Wednesday and Thursday as high
pressure aloft builds in. A cooling trend with more marine
influence is expected for the weekend.

&&

.SHORT TERM (TDY-THU)...13/926 AM.

***UPDATE***

An approaching trough has weakened the marine inversion leading to
a rather haphazard cloud distribution this morning. It will be
another cool day today with temperatures anywhere from 5 to 15
degrees cooler than normal, with the biggest anomalies across the
interior. Could still see some drizzle or light shower near the
upslope areas of the south facing mountains this morning.
Increasing west to northwest winds are expected later this morning
and afternoon, especially near the coast and in the Antelope
Valley with gusts to 30-45 mph possible, strongest in the AV.

***From Previous Discussion***

A tight surface pressure gradient in place yesterday and last
evening brought gusty winds to portions of the area as a weak and
dying boundary dug into the region. Enough of a gradient exists
today to bring gusty west to northwest winds across the Central
Coast, the Ventura County beaches, and into the Antelope Valley.
Wind advisories have been posted for these through 9 pm this
evening. A wind advisory was extended for the Santa Ynez Mountains
and into southwestern Santa Barbara County into late tonight as
winds continue. Some weakening of the winds will likely take place
later this morning and early this afternoon, but the winds
increase again and expand into the greater Santa Barbara area this
afternoon and evening.

A warming trend should start to take shape on Wednesday and
Thursday as 500 mb heights climb over the region. Broad troughing
will remain in place across the region, keeping the air mass from
significantly warming and daytime high temperatures below to near
normal for Wednesday and Thursday. Weaker onshore flow and the
increasing heights will lead to a warming trend over the next
couple of days. This should permit the marine inversion to reform
and keep night through morning low clouds and fog in place.

.LONG TERM (FRI-MON)...13/451 AM.

Higher confidence exists in the pattern for Friday through the
weekend as a cooling trend looks to take shape. Cluster analysis
of the ensemble members suggest broad troughing remaining in place
through the weekend, then the diverging solutions into early next
week. Consequently, there is less spread across the ensemble
members to highlight a cooling trend into Saturday or Sunday.
EPS cloud cover means increase between Friday and Saturday as more
clouds should be expected as the marine layer deepens. EPS cloud
cover means suggest clouds struggling to clear from the land mass
each afternoon. GFS surface pressure gradients agree with this
assessment with KLAX-KDAG surface pressure gradients tightening to
around 9 mb, a value typical with such an occurrence. At this
time, EPS ensemble members suggest marginally gusty winds
developing for KOXR, KSBA, KPMD, and KWJF for the weekend, but
EPS members are highlighting stronger winds for KSDB and through
the Interstate 5 Corridor Sunday night.

By early next week, there is a lot of spread across the ensemble
member temperatures. Cluster analysis reveals the uncertainty and
near equal chances in the height and amount of ridging aloft over
the region. While the slightly more favored solution keeps
troughing in place, it should be noted the majority of the
remaining solutions would lead to a warming trend. EPS members
suggest high temperature means increasing across the region, but
the question is how warm the air mass will get.

&&

.AVIATION...13/1245Z.

Around 1106Z at KLAX, there was no marine layer nor inversion.
There was a deep moist layer above up to around 6200 feet.

Low confidence in the current forecast due to the presence of a
weak marine inversion. Clouds will constantly scatter and reform
at all sites, most likely with MVFR conds through the morning.
There is a 20% chance of MVFR conds at all coastal sites after 08Z
Wed. Winds may be off by +/- 5 mph at any point.

KLAX....Low confidence in TAF. BKN015-025 will constantly scatter
and reform through the morning. There is a 20% chance of BKN015
cigs after 08Z Wed. Good confidence in any east wind component
remaining under 7 kts.

KBUR...Low confidence in TAF. BKN015-025 will constantly scatter
and reform through the morning. There is a 30 percent chance of
southwesterly cross winds greater than 10 knots between 22Z Tue
and 02Z Wed.

&&

.MARINE...13/308 AM.

Steep seas with widespread winds of 25 to 35 knots will continue
through today (up to 10+ feet for the outer waters and PZZ645,
and approaching 7 to 9 feet for the inner waters south of Pt
Conception), with generally hazardous conditions for most vessels
during the afternoon and evening hours. Current Small Craft
Advisories and Gale Warnings look good. While some areas will see
some lulls, steep seas will affect much of the area.

The strongest winds appear focused on the waters from eastern
Santa Cruz Island to Anacapa Island, but will also likely see
strong winds extending to the Ventura County Coast and south to
Point Dume.

Moderate confidence in forecast for the next 3 days...winds plus
or minus 5 knots and seas plus or minus 3 feet, but remaining near
SCA levels, especially across the outer waters.

High confidence in improving winds and seas (heights
remain elevated but periods lengthen) Wednesday through Friday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 9 PM PDT this evening for zones
      340-341-346-347-354-381-383. (See LAXNPWLOX).
     Wind Advisory remains in effect until 3 AM PDT Wednesday for
      zones 349-351-352. (See LAXNPWLOX).
     Wind Advisory in effect from 2 PM this afternoon to 3 AM PDT
      Wednesday for zone 350. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Wednesday for
      zones 645-655-670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 2 PM PDT this afternoon
      for zones 650-673-676. (See LAXMWWLOX).
     Gale Warning in effect from 2 PM this afternoon to 11 PM PDT
      this evening for zones 650-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...MW/Hall
AVIATION...Lund
MARINE...Kittell/Lund
SYNOPSIS...Hall

weather.gov/losangeles

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

NWS LOX Office Area Forecast Discussion