123
FXUS66 KLOX 261813
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1113 AM PDT Wed Jun 26 2024

Updated Aviation and Marine Sections

.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...26/1811Z.

At 17Z over LAX, the marine layer was 1000 feet deep. The top of
the inversion was 4000 feet and 23 degrees Celsius.

While all sites are VFR now, there is a chance of BKN010 reforming
today as early as 20Z at KOXR (30%) and KLAX (10%).

High confidence in VFR conditions through Thursday at KPRB KWJF
KPMD, moderate confidence at KBUR KVNY. All other sites have a
chance ceilings tonight into Thursday: KSBP (60%) KSMX (90%) KSBA
(50%) KOXR (80%) KCMA (70%) KSMO (50%) KLAX (50%) KLGB (50%). High
confidence that ceilings and visibilities will be similar for the
next 24 hours as they have been for the previous 24 hours. Winds
will be stronger today than yesterday at KSMX KSBP, and KWJF KPMD
where the wind directions will likely have a more northerly
component.

KLAX...Moderate confidence in VFR conditions through at least 04Z,
with a 10% chance of a couple of hours of BKN010 20-02Z. Low
confidence on ceilings tonight. 50% chance of BKN008-012 starting
as early 03Z and as late 10Z. Southeast winds will likely form
after 09Z, but high confidence that they will stay under 8 knots.

KBUR...There is a 10% chance of IFR ceilings Thursday 10-15Z,
otherwise high confidence VFR conditions through at least
Thursday. High confidence in seasonal winds.

&&

.MARINE...26/1111 AM.

Dense fog will impact the waters off the Central Coast this
morning, with reduced visibilities possibly lasting through the
afternoon and evening. There is a moderate threat for dense fog
again on Thursday for the same area.

High confidence in at least Small Craft Advisory (SCA) winds and
seas through Friday Night for the Outer Waters (offshore waters
of the Central Coast to San Nicolas Island). There is a 60 percent
chance of reaching Gales tonight, especially the northern most
areas. For Thursday, the chance for Gales increases to 90 percent
for that area. High confidence in Gales ending by Friday morning.
Moderate confidence in much less wind on Saturday, but winds will
pick up again on Sunday.

Elsewhere there the SCA level northwest winds will push into the
Santa Barbara Channel but high confidence that they will stay
confined to the western half. There is a chance that enough of the
channel will be covered with these winds to warrant an SCA...20
percent chance tonight and 40 percent chance on Thursday Night.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Friday for
      zones 645-676. (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).

&&

$$

PUBLIC...DB
AVIATION...Kittell/Lewis
MARINE...RK
SYNOPSIS...jld

weather.gov/losangeles

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