504
FXUS66 KLOX 261657
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
957 AM PDT Wed Jun 26 2024

.SYNOPSIS...26/922 AM.

Expect cooling temperatures through Friday as high pressure
weakens over the area and onshore flow strengthens. Night through
morning low clouds and fog will become more widespread through the
end of the week. Warmer weather is expected over the weekend and
into early next week as high pressure returns.

&&

.SHORT TERM (TDY-FRI)...26/928 AM.

***UPDATE***

The marine layer clouds never really made an appearance in LA
County this morning, and an eddy is keeping the Santa Barbara area
covered. Temperatures are 3-5 degrees cooler this morning than
yesterday as the cooling trend kicks off. The exception is in the
LA County mountains which had more cloud cover yesterday.  No
other impactful changes from the previous forecast.

***From Previous Discussion***

Low clouds have become widespread in coastal areas N of Pt.
Conception, and were beginning to push into the Santa Ynez Valley.
S of Pt. Conception, the stratus field was less organized, but
some clouds have pushed into coastal areas from southeastern SBA
County to western L.A. County. Clouds should become more
widespread in these coastal areas by daybreak, and could even
push into the lower valleys of VTU County and the San Gabriel
Valley for a few hours. Pressure gradients between KLAX and KDAG
were moderately onshore, slightly more so that at this time
yesterday morning. Expect skies to clear by mid morning in the
valleys and late morning across most of the coastal plain. Clouds
could linger at some beaches into the afternoon hours, but even
there, skies should eventually become mostly sunny today.

The forecast area was sandwiched between the western periphery of
a large and strong upper high over New Mexico, and an upper low
well of the coast of the Pacific Northwest, with a broad west
southwesterly flow pattern aloft overhead. Heights today will
change little from those on Tue, but onshore gradients between
KLAX and KDAG will be slightly stronger this afternoon. In
addition, temps at 950 mb will drop a degree or two. With the
addition of some extra marine influence to start the day, expect a
couple of degrees of cooling in most areas west of the mtns
today, with the best cooling across the coastal plain. Max temps
should change little in the mtns and the Antelope Valley. N-S
gradients will increase across SBA County and thru the I-5
Corridor later today and tonight, so expect some gusty NW to N
winds across the western portions of the south coast of SBA
County, the western Santa Ynez mtns and thru the I-5 Corridor.
Winds are expected to remain below advisory levels in most areas.

The upper low in the Pacific will move into the Pac NW late
tonight/Thu, with a trough extending southward into the forecast
area. Expect the marine layer to deepen a bit tonight, and clouds
should be widespread in coastal areas (with the possible exception
of the south coast of SBA County due to the northerly flow.
Clouds will have a better chance at pushing more forcefully into
the valleys tonight. There could even be some local drizzle,
mainly south of Pt Conception. Expect somewhat slower clearing of
the low clouds Thu, with a better chance that clouds will linger
at some beaches. With lowering heights and cooling at 850 mb and
950 mb, expect a few degrees of cooling just about everywhere Thu.
The exception may be on the south coast of SBA County, where
temps may edge upward due to downslope northerly flow.

A broad trough will linger across the region Thu night and Fri.
N-S gradients will peak across SBA County and in the
VTU/northwestern L.A. County mtns Thu evening, and winds could
reach advisory levels in some areas. Elsewhere, expect little
change from tonight/Thu morning, except that low clouds may be a
bit more widespread in the valleys. Once again, due to northerly
flow, clouds may be limited across southern SBA County or arrive
very late Thu night. Expect the clearing pattern Fri to be
similar to that on Thu. Additional slight height falls and
slightly cooling at 850 mb/950 mb may allow for a bit more
cooling in most areas Fri.

.LONG TERM (SAT-TUE)...26/508 AM.

Heights will rise across the region over the weekend as a large
upper high in the south central U.S. begins to expand westward.
Expect the marine layer to become increasingly shallow, with less
in the way of inland and valley low clouds each night. In fact,
low clouds may be squeezed out of most valley areas by Sat
night/Sun morning. Rising heights/thicknesses, weakening onshore
flow, and less low cloud coverage should lead to a few degrees of
warming both Saturday and Sunday. On Sun, max temps will probably
exceed 100 degrees in the Antelope Valley and the interior valleys
of SLO County, with highs near 100 degrees in some of the warmer
locations in the valleys of VTU and L.A. Counties.

Heights will remain quite high across the region Mon and Tue,
although they will lower a bit as the upper high weakens and
shifts eastward. In addition, onshore flow will increase each day.
Expect a few degrees of cooling Mon and Tue, especially west of
the mtns, with a possible increase in the coverage and inland
extend of night through morning low clouds and fog.

N-S gradients will increase Sun night and Mon night, which could
bring some gusty winds to southern SBA County and the I-5
Corridor, along with a reduction in coastal stratus in southern
SBA County.

&&

.AVIATION...26/1102Z.

Around 0730Z, the marine layer was around 900 feet deep at KLAX.
The top of the marine inversion was around 3000 feet with a
temperature near 23 degrees Celsius. There was another inversion
above up to around 4500 feet.

Moderate confidence in the current forecast for coastal terminals
south of Point Conception, otherwise high confidence in the
current forecast. LIFR to IFR conditions will be prevalent at
coastal terminals, higher south of KSBA.

KLAX...IFR conditions will continue through at least 17Z. There
is a 30 percent chance of IFR to MVFR conditions lingering past
17Z until as late as 22Z. An early return of IFR conditions should
be expected as early as 02Z Thursday, or as late as 06Z Thursday.
No wind impacts are expected at this time.

KBUR...VFR conditions are expected through the period. No wind
impacts are expected at this time.

&&

.MARINE...26/352 AM.

Moderate to high confidence in the current forecast. Higher
confidence in seas relative to winds.

Northwest winds will increase through Thursday. There is a 80 to
100 percent chance of Small Craft Advisory (SCA) level winds by
this afternoon for the waters southwest through northwest of the
Channel Islands and the nearshore waters along the Central Coast
and lasting into late Thursday night. There is a 50-60 percent
chance of the northwest Gales west through northwest beyond 10 NM
from the Central Coast shoreline this evening through Thursday
night, extending farther to the south on Thursday afternoon and
evening.

Inside the southern California bight, there is a moderate-to-high
(30-50 percent) chance of SCA levels winds for the western Santa
Barbara Channel, dropping off a nil-to-low chance (0-20 percent)
chance to the east and southeast. Chances will increase by about
10 percent on Thursday and Thursday evening.

Areas of dense fog will affect most of the coastal waters this
morning with the highest likelihood to the southwest through
northwest of the Channel Islands and the nearshore waters along
the Central Coast this morning. There is a low-to-moderate chance
of similar dense fog tonight and into Thursday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 1 PM this afternoon to 3
      AM PDT Friday for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 5 PM PDT this afternoon
      for zone 670. (See LAXMWWLOX).
     Gale Warning in effect from 5 PM this afternoon to 8 AM PDT
      Thursday for zone 670. (See LAXMWWLOX).
     Gale Watch in effect from Thursday morning through late
      Thursday night for zone 670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 PM PDT Thursday for
      zone 673. (See LAXMWWLOX).
     Gale Watch in effect from Thursday afternoon through late
      Thursday night for zone 673. (See LAXMWWLOX).
     Small Craft Advisory in effect from 2 PM this afternoon to 3
      AM PDT Friday for zone 676. (See LAXMWWLOX).

&&

$$

PUBLIC...DB
AVIATION...Hall
MARINE...Hall
SYNOPSIS...jld

weather.gov/losangeles

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