-- Discussion containing changed information from previous version are highlighted. --
104
FXUS66 KLOX 071727
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1027 AM PDT Fri Jun 7 2024

.SYNOPSIS...07/919 AM.

Night and morning Low clouds and fog with areas of drizzle will
continue across coast and valleys into next week, clearing to
within a few miles of the beaches by afternoon. While
temperatures will be a few degrees below normal near the coast,
temperatures will be warmer over interior sections. Precipitation
is not expected over the region through at least the middle of
next week.

&&

.SHORT TERM (TDY-SUN)...07/925 AM.

***UPDATE***

No significant updates this morning. Marine layer depth up to
around 2300 feet in the LA Basin, sloping down to around 1300 feet
across SB/SLO Counties. Pressure gradients continue to trend
onshore while high pressure weakens, leading to cooler
temperatures, stronger afternoon sea breezes, and slower clearing
of low clouds. Inland temperatures are already down 5-10 degrees
this morning from 24 hours ago, and while some recovery is
expected this afternoon, highs should still end up down around 5
degrees on average for inland areas.

***From Previous Discussion***

Upper level heights are expected to continue to fall gradually
over the next few days, with a moisture-starved trough reaching
the region by Sunday. However, the overall weather pattern will be
quite similar through the weekend, and dropping daytime high
temperatures will be the most notable difference day-to-day. For
interior locations (i.e., deserts, mountains, and most valleys),
temperatures will fall several degrees each day through the
weekend, bottoming out on Sunday with max temperatures below
normal by around 2 to 6 degrees. One exception will be Paso
Robles, which is likely to see another drastic 10+ degree drop in
temperatures today, as a cool southerly seabreeze will moderate
temperatures. Coastal areas will be much less affected by the
cooling airmass aloft. Strong onshore pressure gradients are
forecasted through the period. This will drive continued marine
layer clouds and strong sea breezes, which will keep temperatures
relatively constant at the coasts through the weekend (mid 60s to
low 70s).

The marine layer is currently around 1700 ft deep with a strong
inversion aloft, which is significant lifting by a Catalina Eddy
compared ydy evening. The lifting will make drizzle possible this
morning for LA and Ventura Counties. Low clouds are currently
creeping inland, and have reached the Santa Clarita Valley and
foothill locations. Clearing is expected to occur by the late
morning or early afternoon each day, except for beaches where
clouds are likely to persist all day. No major changes in cloud
cover through the weekend, except for slight deepening (further
inland extent) each day.

There is good agreement between the GFS and ECMWF that a cutoff
low will to set up to the southwest of SoCal Sunday night. This
cool low pressure system has the potential to disturb the warm
capping inversion and scattering out the marine layer. The more
likely scenario is that the system will lift the marine layer
which would result in overnight- to- morning drizzle.

The strong onshore pressure gradients will continue to drive
southwest winds across the Antelope Valley and foothills. Wind
gusts 30 to 40 mph will be common, and gusts up to 45 mph are
possible for the foothills. A Wind Advisory has been issued for
this afternoon into tonight for the western Antelope Valley
foothills, as the local enhancement for this zone may result in
advisory level wind gusts with little upper level support.

.LONG TERM (MON-THU)...07/338 AM.

Next week there is high model agreement that the dominant
synoptic feature will be a cut off low, that is likely to stall
to the southwest of the region before slowly traveling eastward.
The center of the low pressure system will pass either to the
south or directly over SoCal on Thursday or Friday. Overall
weather conditions will be fairly constant during the period. At
the surface, strong onshore pressure gradients are expected to
continue.

The marine layer pattern will be similar each day, as June Gloom
will prevail. Overnight and morning clouds will extend over coasts
and valleys and up to the foothills. Daytime clearing and
sunshine is likely by midday, except with strong onshore gradients
clouds may continue to cling to the beaches all day. High
temperatures will show dramatic differences from the coasts to the
deserts. Expect 60s to low 70s at the beaches, 70s to low 80s for
the valleys, and in the 90s in the Antelope Valley.

The cutoff low has the potential to lift the marine layer, thus
drizzle is possible each night into morning. During the afternoon,
instability brought about by the low pressure system may yield
cumulus cloud development over the mountains, but with little
mositure, showers are unlikely at this time. Towards the latter
part of the week, when the upper low has a chance of passing
directly over the region, there is a chance that the low pressure
will disturb the capping inversion and scatter out the marine
layer, leading to widespread clearing.

&&

.AVIATION...
-- Changed Discussion --
07/1727Z.

At 1700Z at KLAX, the marine layer was 2500 ft deep. The top of
the inversion was at 5400 ft with a temperature of 23 degrees C.

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

Moderate confidence in other coastal and valley TAF sites. Timing
of flight category changes could be +/- 2 hours of current
forecasts. There is a 20-30% chance of VFR conditions at KLAX,
KSMO and KOXR 21Z-02Z.

KLAX...Moderate confidence in 18Z TAF. There is a 20-30% chance of
VFR conditions 21Z-03Z. For tonight, timing of flight category
changes could be +/- 2 hours of current forecasts. There is a 50%
chance that CIGs will not drop to LIFR levels. No significant
easterly wind component is expected.

KBUR...Moderate confidence in 18Z TAF. Timing of return of
IFR/LIFR conditions tonight could be +/- 2 hours of current
forecasts.
-- End Changed Discussion --

&&

.MARINE...07/725 AM.

For the Outer Waters, moderate to high confidence in current
forecast. Tonight through Saturday high confidence in winds and
seas remaining below Small Craft Advisory (SCA) levels. For Sunday
and Sunday night, there is a 40-50% chance of SCA level winds.
For Monday and Tuesday, high confidence in winds and seas
remaining below SCA levels.

For the Inner Waters north of Point Sal, high confidence in
current forecast. Today through Tuesday, winds and seas are
expected to remain below SCA levels.

For the Inner Waters south of Point Conception, high confidence
in current forecast. Today through Tuesday, winds and seas are
expected to remain below SCA levels.

Through the weekend, dense fog, with visibility of one mile or
less, will continue to impact the coastal waters north of Point
Conception during the night and morning hours.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect from 3 PM this afternoon to 3 AM PDT
      Saturday for zone 381. (See LAXNPWLOX).
     Heat Advisory remains in effect until 8 PM PDT this evening
      for zones 382-383. (See LAXNPWLOX).
PZ...NONE.

&&

$$

PUBLIC...MW/Schoenfeld/Rorke
AVIATION...RAT
MARINE...RAT
SYNOPSIS...MW

weather.gov/losangeles

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