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259
FXUS66 KLOX 221621
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
921 AM PDT Sun Sep 22 2024

.SYNOPSIS...22/342 AM.

A warmer and drier pattern will establish through Monday as high
pressure aloft builds over the region. A warmer air mass will
likely remain in place through much of the week away from the
coast, with the hottest daytime temperatures forecast for Monday.
Onshore flow will persist through the period, maintaining night
through morning low clouds and fog for coastal areas and some of
the valleys.

&&

.SHORT TERM (TDY-TUE)...
-- Changed Discussion --
22/920 AM.

***UPDATE***

The marine inversion this morning ranged from 1400 ft deep at VBG
and around 1800 ft deep at LAX. Low clouds and fog covered the
coast and into some of the adjacent vlys thru mid morning. The low
clouds are expected to clear back to or off the coast by midday
with some low clouds possibly lingering along the Central Coast
beaches this afternoon. Elsewhere and otherwise, mostly sunny
skies will prevail across the region today. Breezy onshore winds
are expected this afternoon as well.

Temps this afternoon will be a few degrees below normal for the
coast and adjacent vlys, and a few degrees above normal for the
interior vlys, mtns and deserts. Much of the inland coast and vlys
should reach the 70s and 80s today, except the warmest vlys will
likely reach into lower 90s.

***From Previous Discussion***

584 dam hgts will persist through Tuesday as a weak high hgt upper
pinches off and retrogrades a 100 miles west of Pt Conception. The
weak sfc reflection of the low will help bring offshore trends
and even weak offshore flow in the morning hours to the area esp
Monday.

Offshore trends will continue on Monday and there will be less
marine layer clouds and an even quicker burn off. This will allow
for another 3 to 6 degrees of warming. Monday will be the warmest
day of the next 7 with max temps 3 to 6 degrees above normal.

A slight increase in onshore flow and a slight decrease in hgts is
expected Tuesday. This will cool temperatures a couple degrees
across coast and valleys but either little change or slight
warming across the interior.

.LONG TERM (WED-SAT)...22/330 AM.

Not much excitement on tap in the extended period. The faster more
dynamic flow will be well to north and there will be weak flow
over Srn CA. Gradients Wed to Fri to the east will increase to
moderate but the N/S grads will remain weak and may even be
slightly offshore in the morning hours. There will be better
onshore trends on Saturday. The night through morning low clouds
pattern will continue over the coasts will local penetration into
the lower vlys (esp the Santa Ynez Vly).

Look for 3 to 5 degrees of cooling Wednesday with the increase in
onshore flow. Thursday`s temps will be very similar to Wed`s.
Perhaps some barely noticeable warming Friday and then 2 to 3
degrees of cooling on Saturday as there is another noticeable
increase in the onshore flow both to the north and east.

In general max temps will be above normal across the interior but
a few degrees blo normal across the coasts and vlys.
-- End Changed Discussion --

&&

.AVIATION...22/1040Z.

Around 0715Z, the marine layer depth was around 1200 feet deep at
KLAX. The top of the marine inversion was around 2100 feet with a
temperature near 18 degrees Celsius. There was another inversion
above up to around 4100 feet.

High confidence in the current forecast for desert terminals,
otherwise moderate confidence in all other terminals. Higher
confidence in flight categories. Less confidence in timing. LIFR
to IFR conditions at terminals north of Point Conception and IFR
to MVFR conditions will continue at terminals south of Point
Conception through at least 16Z. Timing of clearing could off by
up to four hours. There is a moderate chance of LIFR conditions
at terminals north of Point Conception through 14Z. Farther to the
south, there is a low-to-moderate chance of VFR conditions
continuing at Los Angeles County valley terminals. There is a
high-to-likely chance of LIFR to IFR conditions returning tonight
and into Monday morning.

KLAX...IFR to MVFR conditions will continue through at least 20Z,
and possibly as late as 23Z. There is a 20 percent chance that
KLAX may not clear at all. A return of IFR to MVFR conditions
could occur as soon as 01Z or as late as 03Z. Higher confidence
exists in IFR conditions after 03Z.

KBUR...There is a 20 percent of VFR conditions continuing through
the period, otherwise IFR to MVFR conditions will spread into KBUR
as soon as 1130Z, or as late as 13Z. VFR conditions will develop
between 16Z and 17Z.

&&

.MARINE...
-- Changed Discussion --
22/911 AM.

High confidence in the current forecast through Wednesday, then
moderate confidence thereafter. Winds and seas will remain below
Small Craft Advisory (SCA) levels through at least Wednesday,
except for 30-50% chance of local SCA level wind gusts near Pt
Conception and the San Pedro Channel this afternoon thru evening.
There is also a 20-30% chance of SCA level winds for the inner
waters off the LA and OC Coasts in the afternoon thru evening
Wednesday. Then, moderate to high confidence in winds and seas
increasing to SCA level Thursday thru Friday, with highest
confidence in the Outer Waters (Central Coast south to San Nicolas
Island) Friday.
-- End Changed Discussion --

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...Rorke/Sirard
AVIATION...Hall
MARINE...Lewis/Hall
SYNOPSIS...Smith/Hall

weather.gov/losangeles

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