303
FXUS66 KLOX 161757
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1057 AM PDT Fri Aug 16 2024

.SYNOPSIS...16/225 AM.

A high pressure system over the region will weaken and move east
over the coming days as an upper-level trough moves into the
Pacific Northwest. A cooling trend with increased onshore flow
will continue through the weekend, then some warming will develop
over the early half of next week.

&&

.SHORT TERM (TDY-SUN)...16/850 AM.

***UPDATE***

The forecast is well on-track, and no changes have been made to
the ongoing forecast.

***From Previous Discussion***

Very benign weather will continue across Srn Ca for the 3 day
short period. Over the next three days an upper high over the
CA/AZ border will shift to the east while at the same time an
upper low to the N will move southward. The effects over SRN CA
will be a switch to SW flow aloft that will strengthen with time.
594 dam hgts this morning will fall to 588 dam by Saturday
afternoon and then rebound slightly Sun. At the sfc there will be
weak to moderate onshore flow to the east and weak occasionally
offshore flow in the N/S direction.

Marine layer cloud coverage is a little more robust that it has
been over the last few nights. A weak eddy has spun up and there
are some low clouds moving from Long Beach into the Oxnard. Low
clouds should increase further tonight into Saturday morning as
hgts lower. The low cloud coverage will shrink Sunday morning as
the offshore flow from the north increases slightly.

The onshore push to the east will be a little stronger today and
this will cool the coasts a few degrees. Northerly flow however
will bring warmer air into the interior where max temps will warm
3 to 4 degrees. Look for 2 to 4 locally 5 to 6 degrees of cooling
Saturday as the hgts lower and onshore increases. Less marine
layer, slightly higher hgts and a stronger offshore push from the
north will bring a little warming to the area Sunday.

Last evenings Sundowner event did not live up to expectations with
gusts almost all in the 30 to 40 mph range. The winds will be
weaker tonight and there is not threat of advisory winds.

Monsoonal thunderstorm activity is not favored through the
weekend, although the outer edge of a moisture surge may bring
some high clouds to the region tomorrow afternoon. This moisture
is expected to be too elevated to increase thunderstorm chances,
which continues to be well under 10 percent.

.LONG TERM (MON-THU)...16/309 AM.

The latest deterministic mdls and ensembles are in good agreement
on the general upper level pattern for the xtnd period. The upper
high will strengthen and move to the west on Monday and Tuesday.
On Wednesday and Thursday a PAC NW trof will move into the state
and push the upper high back to the east.

Hgts will climb each day through Tuesday and will peak around 595
dam on Tuesday afternoon. to 595 dam. Look for 2 to 4 degrees of
warming each day. By Tuesday afternoon the only 70s will be right
at the beaches with 80s and lower 90s across the rest of the
coasts. The vlys will see max temps from 92 to 104 degrees. There
will be plenty of triple digit heat across the far interior and
lower mtn elevations as well. These temps are about 6 degrees
above normal. While it will be warm these temps will only pose a
moderate heat risk. There is a 15 percent chc that the current
temp forecast is too low and there would be a need for heat
products across the interior and some of the vlys.

Lowering hgts and onshore flow will arrive Wed and continue into
Thu. Look for 2 to 4 degrees of cooling each day.

The significant high pressure will likely suppress most if not
all marine layer clouds on Mon and Tue. The lowering hgts will
bring an more conducive environment for low cloud formation Wed
and Thu mornings.

Monsoonal moisture transport into the region becomes a bit more
likely on Tuesday. Even so, at this point the chance of actual
convection remains less than 10 percent.

&&

.AVIATION...16/1756Z.

At 1646Z at KLAX, the marine layer was 1300 ft deep. The top of
the inversion was 2700 ft with a temperature of 24 deg C.

High confidence in 18Z TAFs for KPRB, KBUR, KVNY, KPMD, and KWJF.

Moderate confidence in Los Angeles County coastal TAFs. Arrival of
cigs may be off +/- 3 hours from current forecasts. Cig/vsby
restrictions may bounce between VFR-IFR between 04Z and 10Z. There
is a 30% chance cigs arrive by 04Z as IFR.

Low confidence in remaining coastal TAFs. Arrival of cigs may be
off +/- 4 hours from currents forecast and minimum flight cat may
be off by 1 cat at any time after cigs arrive. There is a 30%
chance of VLIFR conditions at KSMX and KOXR at any point after
cigs arrive. There is a 20% chance KSBP remains VFR thru the
period.

KLAX...Moderate confidence in the 18Z TAF. There is a 30% chance
that cigs below 010 arrive by 04Z and a 20% chance of cigs below
005 with vsbys as low as 4SM between 09Z and 15Z. Flight cats may
bounce between VFR-IFR, especially between 04Z and 09Z. There is
a 30% chance of VFR conditions by 16Z. No significant east wind
component is expected.

KBUR...High confidence in 18Z TAF.

&&

.MARINE...16/928 AM.

For the offshore waters from the Central Coast to San Nicolas
Island (the outer waters), high confidence in SCA level winds for
the two southern zones through Monday. For the furthest northern
zone, high confidence in SCA level winds through tomorrow morning,
with moderate confidence in SCA level winds continuing thru
Monday.

For the nearshore waters off the Central Coast, moderate
confidence in SCA level winds through this evening. Moderate
confidence in conditions remaining below SCA levels through the
Monday.

For the Santa Barbara Channel, high confidence in winds below SCA
levels through Saturday. Moderate confidence of SCA level winds
occuring in the Western Portion of the channel in the afternoon
thru late night hours on Saturday. Then, high confidence in winds
remaining below SCA levels Sunday thru Monday. In the eastern
portion, high confidence in conditions remaining below SCA level
through the Monday.

For the southern inner waters, high confidence in conditions
staying under SCA levels through Monday.

With a shallow marine layer, there is moderate confidence in
patchy dense fog with visibilities under 1 nautical mile
effecting the Central Coast waters and southern inner waters
tonight thru tomorrow morning.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 9 PM PDT this evening
      for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 AM PDT Saturday for
      zone 670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Monday for
      zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Rorke/Cohen
AVIATION...Lewis
MARINE...Lewis/Kittell/Sirard
SYNOPSIS...Hall

weather.gov/losangeles

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