641
FXUS66 KLOX 090716
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1216 AM PDT Sun Jun 9 2024

.SYNOPSIS...08/940 PM.

An onshore flow pattern will keep cooler temperatures and a
persistent and deep marine layer in place through Sunday, then high
pressure aloft will warm temperatures and decrease onshore flow
for early next week. Otherwise, night through morning low clouds
will continue across the coast and valleys through the middle of
next week.

&&

.SHORT TERM (SUN-WED)...08/859 PM.

***UPDATE***

Currently, an upper level trough is starting to nudge into the
area and will move across the area the next several days. An
upper level cut-off low will slice off the main trough as it runs
into a ridge of high pressure to the east, then hang out off the
coast of southern California, contributing to onshore flow.

For areas south of Point Conception, the marine layer will likely
deepen tonight into Sunday due to lowering upper level heights
with the incoming trough. For areas north of Point Conception, the
marine layer will actually shrink a bit, likely due to the
influence of the high pressure to the east. The dynamics of the
cut-off low will interact with the marine layer to squeeze out
some drizzle across coastal areas and foothills, thus have upped
PoPs (though still less than a mentionable chance) and added
drizzle and patchy fog to the forecast overnight through Sunday
morning. Delayed clearing is likely for most coastal areas, but
there is a chance that the Central Coast could clear out a bit
earlier.

Temperatures today were as expected for the most part with the
exception of San Luis Obispo County where the marine layer
influence was a little more than what the forecast models
suggested - keeping temperatures a few degrees cooler than
forecasted. With the idea that the marine layer will be shrinking
north of Point Conception, decided to keep temperatures on the
warmer side for San Luis Obispo County tomorrow outside the marine
layer. Otherwise, high temps tomorrow are expected to be in the
high 60s at the coasts, in the 70s away from the coasts, and high
80s to low 90s for the far interior areas.

***From Previous Discussion***

Marine layer was up to 3000 feet this morning and there were
numerous areas that had a thick layer of drizzle this morning that
resulted in measurable amounts of rain, mostly 0.05" or less.
Clouds are again slow to clear and temperatures are well below
normal for coast and valleys. The trough over the eastern Pacific
that is causing all this will be moving closer to the coast
tonight and Sunday so look for very similar conditions again
Sunday morning. However, there is some hope for earlier clearing
and slightly warmer temperatures, at least for areas away from the
immediate coast, as onshore gradients weaken in response to
strong high level easterly flow that will push the low farther
offshore and south.

These trends will continue into Monday, then peak Tuesday which
should be the warmest day at least in the short term forecast.
Morning onshore flow is expected to be half what it was today and
with warming aloft we should see the marine layer drastically
lowering early next week. Marine layer clouds are still expected
to push into the valleys for at least a few hours in the morning
and coastal areas may still struggle to clear in the afternoon.
But daytime highs by Tuesday will be back in the lower 100s for
the Antelope Valley and lower 90s for the warmer coastal valleys.
Interior parts of the coastal plain should reach the mid to upper
70s.

.LONG TERM (THU-SUN)...08/200 PM.

Another warm day expected for inland areas Wednesday, though
probably slightly cooler as gradients start trending onshore as
the upper low to our southwest begins to wobble back east. The
cooling trend will really kick into gear Thursday as the upper
low passes right overhead, resulting in another 3000 foot marine
layer, possible morning drizzle, slow clearing, and well below
normal temperatures.

These conditions will be relatively short-lived however as the
upper low is expected to scoot east rather quickly with rapidly
building high pressure aloft and also increasing northerly flow.
Models have been showing weakening onshore flow to the east and
offshore flow to the north, though the latter wasn`t as strong as
earlier runs had shown. At the very least we should be looking at
widespread warming, even for coastal areas Friday and Saturday
with at least a 40-50% chance of strong Sundowners in the Santa
Barbara area and triple digit heat across the interior. The 12z
GFS is still showing 25-40kt north winds coming across the Santa
Ynez Range Friday evening with 950 mb temps in the low 90s. Will
have to be monitoring that situation this week for possible fire
weather hazards at the end of the week.

&&

.AVIATION...09/0714Z.

At 0550Z at KLAX, the marine layer was 2200 ft deep. The top of
the inversion was at 5600 ft with a temperature of 20 degrees C.

High confidence in desert TAFs.

Low to moderate confidence TAFs for coastal and valley sites.
Timing of flight category changes could be off by +/- 2 hours.
There is a 25 percent chc that coastal sites with no clearing fcst
may see a few hours of afternoon clearing. From 08Z-15Z cigs may
be 1 flight cat higher than fcst.

KLAX...Moderate confidence in TAF. Timing of flight category
changes could be off by +/- 2 hours. There is a 25 percent
chance of BKN008 conds 11Z-14Z. No significant easterly wind
component is expected.

KBUR...Moderate confidence in TAF. There is a 25 percent
chance of cigs remaining AOA 010. There is a 20 percent chc of VFR
conds developing by 18Z and a 30 percent chc by 19Z.

&&

.MARINE...08/945 PM.

Moderate to high confidence in the current forecast.

For the Outer Waters, there is a 60-80 percent chance of Small
Craft Advisory (SCA) level winds through early Monday, then winds
and seas remain below SCA levels between Monday and Thursday.

For the Inner Waters north of Point Sal, there is a 60-70 percent
chance of SCA level winds Sunday afternoon and evening, then
winds and seas will remain below SCA levels between late Sunday
night and Thursday.

For the Inner Waters south of Point Conception, there is a 30-40
percent chance of SCA level winds late Sunday afternoon and
evening, highest across the western half of the Santa Barbara
Channel. Then, winds and seas should remain below SCA levels
between late Sunday night through Thursday.

&&

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

&&

$$

PUBLIC...Lund/Hall/MW
AVIATION...Rorke
MARINE...Hall
SYNOPSIS...Hall

weather.gov/losangeles

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