-- Discussion containing changed information from previous version are highlighted. --
988
FXUS66 KLOX 110444
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
944 PM PDT Mon Jun 10 2024

.SYNOPSIS...10/838 PM.

Temperatures Tuesday are expected to warm a few more degrees as
high pressure builds and onshore flow weakens. Cooler temperatures
are expected Wednesday and Thursday as an upper low moves through
causing the marine layer to deepen. Then turning warmer again
Friday through the weekend with locally gusty northerly winds.

&&

.SHORT TERM (MON-THU)...10/837 PM.

Significant warming started today as onshore flow weakened in
response to building high pressure aloft. Several interior
observation sites climbed into the lower to mid 90s today.
Meanwhile, at the coast temperatures were about the same as
yesterday with slow clearing of low clouds and fog and a chilly sea
breeze. 00Z Vandenberg sounding showing marine layer depth around
1500 feet, while ACARS sounding showing marine layer depth around
1900 feet this evening. With building heights and weakening
onshore pressure gradients, the marine layer depth is expected to
shrink overnight into Tuesday morning. Current satellite imagery
showing low clouds surging quickly into the coastal areas this
evening and will likely spread into most coastal valleys tonight.
Model cross section showing marine layer depth becoming more
shallow north of Point Conception tonight, which could lead to
some patchy dense fog. On Tuesday afternoon, low clouds will
likely linger near some of the beaches as the marine inversion
lowers and strengthens. There will likely be an addition 4-8
degrees of warming for inland areas on Tuesday, with Antelope
Valley climbing to above 100 degrees.

*** From previous discussion ***

Models remain consistent indicating increasing onshore flow
Wednesday as the upper low to our southwest starts to move back
towards the coast. There is still some uncertainty how much
cooling will happen Wednesday but most of the ensemble solutions
show 2-4 degrees of cooling across inland areas and little change
at the coast. More significant cooling Thursday as the upper low
is overhead and onshore gradients to the east bounce back up to
around 10mb in the afternoon. The marine layer will increase to
around 3000 feet again with some morning drizzle possible across
coast and valleys.

.LONG TERM (FRI-MON)...10/207 PM.

The upper low will move quickly through the area Thursday with
building heights Friday and Saturday and weakening onshore flow.
Models have been consistent showing a significant increase in
northerly flow across the western portion of forecast area. Models
weren`t quite as warm today as they have been the last few days
but forecast 950mb winds have increased to 50-60kt just west of Pt
Conception and northerly gradients have jumped to almost 5mb,
peaking early next week at close to 6mb. Humidities will be
dropping across the interior as well as portions of the Santa
Barbara south coast as the Sundowner winds funnel through the
passes and canyons. Winds will be increasing across the northern
LA/Ventura mountains as well but models are definitely focusing on
southern Santa Barbara County for the strongest winds.

Temperatures will be warming up Friday/Saturday and this time
coastal areas will see some of the warming as well, especially in
southern SB County. With the northerly flow in place any marine
layer clouds will be confined to LA and Ventura Counties at most,
and it`s possible it will get pushed south of LA County. Highs
expected to reach the lower 80s across inland parts of the coastal
plain and low to mid 90s in the warmer coastal valleys.

Strong northerly flow will continue across the western areas
into early next week maintaining elevated fire concerns there.
Models show a coastal eddy developing Sunday into Monday that
would increase marine layer for LA/Ventura Counties and cool
temperatures at least a few degrees.

&&

.AVIATION...10/2358Z.

At 2355Z at KLAX, the marine layer was 2000 ft deep. The top of
the inversion was at 4700 ft with a temperature of 21 degrees C.

For the 00Z TAF package, high confidence in desert TAFs and
moderate confidence in coastal and valley TAFs. Lower confidence
for coastal and valley sites due to uncertainties in marine layer.
Timing of flight category changes could be +/- 3 hours of current
forecasts. In latest TAF package, have lowered cigs/vsbys for
several coastal/valley TAF sites due to shrinking marine layer
overnight along with current model guidance.

KLAX...Moderate confidence in 00Z TAF. Timing of flight category
changes could be +/- 3 hours of current forecasts. Also, there is
a 20% chance of LIFR conditions 08Z-14Z time frame. No significant
easterly wind component is expected.

KBUR...Moderate confidence in 00Z TAF. Timing of flight category
changes could be +/- 3 hours of current forecasts. Also, there is
a 20% chance of cigs remaining in IFR category.

&&

.MARINE...
-- Changed Discussion --
10/944 PM.

Moderate to high confidence in the current forecast. Higher
confidence in winds relative to seas.

For the waters southwest through northwest of the Channel Islands,
excluding the nearshore waters along the Central, there is a
high-to-likely (50-60 percent) chance of SCA level conditions
tonight, decreasing to a 20-30 percent chance between Tuesday and
Thursday. An increasing chance of SCA conditions will develop
between Friday and Sunday with a definite (80-100 percent) chance
of SCA conditions by Saturday afternoon and moderate-to-high
(30-50 percent) chance of GALES. There will likely be an extended
period of steep, short period hazardous seas between Friday and
Sunday.

For the nearshore along the Central Coast, winds and sea will very
likely remain below SCA levels through early Friday. Then, there
is a 50-70 percent chance of SCA conditions (winds and seas)
between Friday afternoon and Sunday. There is a low-to-moderate
(20-40 percent) chance of GALES, highest between Saturday
afternoon and Sunday evening.

Inside the southern California, winds and seas will remain below
SCA levels through at least Thursday afternoon, then there is an
increasing chances of SCA level winds between Friday and Saturday.
The chances for SCA levels will increase from a moderate-to-high
(30-50 percent) chance Thursday evening to a 40-60 percent chance
on Friday afternoon and night. Then, SCA chances will increase to
high-to-likely (50-70 percent) on Saturday. The highest chances
are expected through the Santa Barbara Channel during the
afternoon and evening hours. There is a low-to-moderate (20-40
percent) of GALES. There will be a moderate chance of steep,
short period hazardous seas Saturday and Saturday night.
-- End Changed Discussion --

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Tuesday for
      zone 673. (See LAXMWWLOX).

&&

$$

PUBLIC...MW
AVIATION...Gomberg
MARINE...Hall
SYNOPSIS...MW

weather.gov/losangeles

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