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273
FXUS66 KLOX 090401
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
901 PM PDT Sat Jun 8 2024

.SYNOPSIS...08/107 PM.

A deep marine layer will remain in place through the weekend along
with with below normal temperatures. Night and morning low clouds
with drizzle at times will extend well inland with very slow
clearing. Temperates will warm Monday and Tuesday, mainly inland,
as onshore flow weakens.

&&

.SHORT TERM (SAT-TUE)...
-- Changed Discussion --
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 (WED-SAT)...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.
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&&

.AVIATION...09/0101Z.

At 1645Z at KLAX, the marine layer was 2100 ft deep. The top of
the inversion was at 4500 ft with a temperature of 21 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 +/- 3 hours.
There is a 40% chance of VFR conds for KCMA and KOXR through 05Z.
There is a 30-40% chance that CIG/VSBY restrictions will not
develop tonight at KPRB. Generally IFR-MVFR conds are expected,
however there is a 30% chance of LIFR-IFR conds with DZ possible
at coastal/valley sites between 06Z-15Z. There is a 30-40% chance
that VFR conditions will not develop after 18Z for all coastal
sites.

KLAX...Moderate confidence in TAF. Timing of flight category
changes could be off by +/- 3 hours. There is a 40% chance that
CIGs will remain above BKN010 levels. No significant easterly
wind component is expected.

KBUR...Moderate confidence in TAF. Timing of flight category
changes could be off by +/- 3 hours.

&&

.MARINE...08/1223 PM.

For the Outer Waters, moderate to high confidence in current
forecast. Tonight through Monday morning, there is a 60-80% chance
of Small Craft Advisory (SCA) level winds. From Monday afternoon
through Thursday, high confidence in winds and seas remaining
below SCA levels.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. There is a 60-70% chance of SCA
level winds Sunday afternoon and evening. Otherwise, high
confidence in winds and seas remaining below SCA levels through
Thursday.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. For the western half of the Santa
Barbara Channel, there is a 30-40% chance of SCA level winds late
Sunday afternoon and evening. Otherwise for the area, high
confidence in winds and seas remaining below SCA levels through
Thursday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CA...NONE.
PZ...Small Craft Advisory in effect from 3 PM to 9 PM PDT Sunday
      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 Sunday to 3 AM PDT
      Monday for zone 676. (See LAXMWWLOX).
-- End Changed Discussion --

&&

$$

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

weather.gov/losangeles

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