616
FXUS66 KLOX 251819
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1119 AM PDT Wed Sep 25 2024

Updated Aviation Section

.SYNOPSIS...25/939 AM.

Low clouds and fog will continue across coastal areas through the
week with some afternoon clearing and below normal temperatures.
Valley temperatures are expected to be at or below normal for the
remainder of the week, while the far interior areas will remain
above normal. Otherwise, a quiet weather pattern will continue.

&&

.SHORT TERM (TDY-SAT)...25/951 AM.

***UPDATE***

June continues in September across southern California as a trough
remains along the West Coast and onshore flow increases.
Deterministic models continue to advertise weakening onshore flow
the next couple days as high pressure tries to nudge in from the
east, but ensembles are mixed on this idea and forecast soundings
are only showing very minor lowering of the marine layer
depth so confidence is not high that any significant change from
the current conditions will occur.

***From Previous Discussion***

The area will be in between a upper level high to the east and a
large east pac trof to the west with weak SW flow over Srn CA. On
Friday the upper high exerts itself and pushes into the state from
the east. 584 dams hgts today will rise to 590 dam by Friday. At
the sfc gradients will slowly trend offshore as the high pressure
moves closer.

Currently the marine layer is 1600 ft deep and marine layer
stratus covers all of the coasts and most of the vlys including
the Santa Clarita. It will be another day of slow clearing with no
clearing likely at more than a few beaches. Today`s temps will not
change much across the coasts (the SBA south cst will be the
exception as a N to S offshore push will bring some warming). The
Vlys and interior will cool noticeably with 3 to 6 degrees of
cooling like and up to 10 degrees in the Paso Robles area.

The increasing hgts and offshore trends will decrease the marine
layer stratus coverage a little each morning Thu and Fri. Clearing
will be quicker and more complete each day as well. Max temps will
raise a degree or two on Thu and 1 to 3 degrees on Friday.

.LONG TERM (SUN-WED)...25/318 AM.

Decent mdl agreement for the weekend. A weak trof is fcst to swing
into the state and knock the upper high down to the SE. Hgts will
fall to 584 or 585 dam. More importantly onshore flow to the east
will increase to 7 or 8 mb. This surge in onshore flow coupled
with the lowering hgts will bring 2 to 4 degrees of cooling to the
area. The increased onshore flow will also great gusty conditions
across the LA mtns and the Antelope Vly.

Not much change on Sunday. Morning stratus will cover most of the
coasts, otherwise skies will be sunny. Max temps will change
little from Saturday and will be 3 to 6 degrees blo normals across
the csts/vlys and 4 to 8 degrees above normal inland.

The mdls diverge and the ensemble spread increases for the
forecast early next week. Despite the lower confidence in the
exact forecast there is good confidence that the benign weather
will continue. Most likely scenario calls for an upper high and
increasing hgts leading to a two day warming trend. Max temps on
Tuesday could reach into the upper 90s in the warmer vlys.

&&

.AVIATION...25/1818Z.

At 17Z over KLAX, the marine layer was 2000 ft deep. The top of
the inversion was 2800 ft with a temperature of 23 Celsius.

Moderate confidence in similar to slightly low ceilings and
visibility for the next 24 hours as the previous. Slow or no
clearing likely again for KSBA KOXR KSMO KLAX, with a 60-80%
percent chance of 2 hours or less of VFR conditions. Lower chances
of ceilings at KVNY KBUR KPRB tonight compared to last night, but
still a 60% chance of forming. High confidence in VFR at KWJF
KPMD through at least Thursday. Otherwise, high confidence in
ceilings at all other sites, likely dropping to LIFR for at least
a few hours.

KLAX...70% chance of 2 hours or less of VFR conditions today (best
chance for VFR in 20-24Z window), and a 50% chance of no clear at
all. Moderate confidence in similar ceilings and vis tonight as
last night, with IFR most common and a few hours of LIFR 06-14Z.
High confidence in no significant east wind component.

KBUR...60% chance of IFR/LIFR ceilings returning tonight in the
05-09Z window. There is a 30% chance of VLIFR fog 11-15Z.

&&

.MARINE...25/816 AM.

For this afternoon thru late tonight, moderate to high confidence
in winds reaching low end Small Craft Advisory across the western
and southern portions of the Santa Barbara Channel, the two
southern outer waters zones from Pt Conception south to San
Nicolas Island, and the southern inner waters from Anacapa Island
to near Point Dume this afternoon into this evening.

Beyond late tonight, moderate confidence in the forecast.

In the Outer Waters, winds/seas should be below SCA levels late
tonight/Thu morning. There is a 40% chance of SCA conds Thu
afternoon, then SCA conds are likely (60% chance) Thu night thru
Fri morning, with highest confidence in the northern zone off the
Central Coast and the middle zone near Pt Conception. There is a
60% chance of more widespread SCA level winds Friday afternoon
thru late night. Then, winds are expected to be below SCA levels
Sat thru Sun, with a higher chance of SCA winds Sun afternoon thru
evening (20-30%). Seas will build and may get close to advisory
levels (40-50% chance) Sat night thru Sun night.
For the Inner Waters N of Pt. Sal, conds are expected to remain
below SCA levels thru Sun night, with highest chances (30%) of
SCA conditions during the afternoon/eve hours Thu and Fri.

For the Inner Waters S of Pt Conception, SCA conds are unlikely
after this evening. However, there is a 20-30% chance of SCA
level winds Thu afternoon/evening.

Patchy dense fog is possible late tonight/Thu morning. Please
refer to the marine weather statement for more information.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 3 PM this afternoon to
      midnight PDT tonight for zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 9
      PM PDT this evening for zone 655. (See LAXMWWLOX).
     Small Craft Advisory in effect from 5 PM this afternoon to 3
      AM PDT Thursday for zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...MW/Rorke
AVIATION...RK
MARINE...Lewis/DB
SYNOPSIS...MW/Smith

weather.gov/losangeles

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