-- Discussion containing changed information from previous version are highlighted. --
960
FXUS66 KLOX 191754 AAA
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1054 AM PDT Wed Jun 19 2024

updated aviation discussion

.SYNOPSIS...19/857 AM.

Onshore flow will maintain near-normal temperatures across the
region through Thursday with overnight low clouds and fog along
the coastal and valley areas. Expect warm on Friday with above
normal temperatures across the valleys, mountains, and desert
into early next week. Dangerously hot weather is possible across
the interior over the weekend.

&&

.SHORT TERM (TDY-FRI)...
-- Changed Discussion --
19/910 AM.

***UPDATE***

Temperatures are 3-5 degrees cooler along the coast with stronger
onshore flow along the south coast and widespread marine clouds.
In the Antelope Valley, temperatures are up 3-5 degrees with
westerly winds. The central coast was a bit cloudier than expected
this morning, but there are no impactful changes from the
previous discussion.

***From Previous Discussion***

Strong winds in the outer waters coupled with a near shore S to N
sfc pressure gradient has created a decent eddy. The marine layer
is 1500-2000 ft deep and the eddy has pushed low clouds into the
coasts from SBA southward as well as the LA Vlys. By dawn low
clouds should also cover most of the VTA vlys. Additionally some
low clouds have formed from ground cooling across western SBA
county. Onshore flow will increase to 7 or 8 mb to the west in the
afternoon and this may keep some beaches cloudy in the afternoon.
Elsewhere clearing should be complete by noon as the marine
inversion is not that strong. Otherwise hgts will lower slightly
and this along with the more extensive marine layer will bring 2
to 3 degrees of cooling to most of the area.

Strong NW winds coming off the waters of the Central Coast will
filter through the Western Santa Ynez range and produce low end
advisory level gusts across the western half of the SBA south
coast.

Two competing forces will be at work on the marine layer cloud
pattern on Thursday as increasing troffing aloft combines with the
eddy to promote cloud development. On the other hand sfc
gradients will be weaker than they are this morning. Short range
ensemble guidance shows that the eddy will likely be weaker and
this should tip the scales to a clearer forecast. The best chance
for low clouds will be over the southern portion of LA county and
the Central Coast. The offshore trends will delay and weaken the
seabreeze and this will bring 2 to 3 degrees of warming to the
area with the exception of the Central Coast which will cool due
to a more robust marine layer presence. The Summer Solstice will
occur at 151 PM PDT.

Friday will kick off a fairly dramatic warm up as a large and hot
upper high over the middle of the county expands westward. The
eddy looks a little stronger so probably a little more morning
low clouds across the coasts and into some of the lower vlys. By
noon the whole area will be clear. Hgts will climb to 588 dam and
max temps will warm 5 to 10 degrees across the interior and 2 to 4
degrees across the vlys. The coasts will still be under the
marine influence and max temps will not change much. Antelope Vly
residents will see max temps range from 100 to 103 degrees or
about 8 degrees over normal.

.LONG TERM (SAT-TUE)...19/324 AM.

All eyes on the weekend as a significant warm up will likely
occur. A very large and warm upper high will move over AZ/NM and
Srn CA will be covered by the upper high`s western half. Hgts will
be near 592 dam. There is no offshore flow and in fact there will
be fairly strong onshore flow (esp to the east) This will result
in a very different temperature forecast for the interior vs. the
coasts. The high hgts will really smoosh the marine layer down
and create a very strong inversion. Such strong inversions are
hard to break down and this could keep clouds at the beach all day
long. The marine layer will be under 1000 ft and this will keep it
out of most if not all of the vlys. The very steep inversion will
also keep min temps much warmer than normal right at the top of
the inversion so locations near 1000 ft in elevation will see
these very warm overnight lows. Look for 3 to 6 degrees of warming
on Saturday away from the beaches. Max temps across the interior
will end up 6 to 12 degrees above normal while the vlys will be 2
to 4 degrees above normal. The beaches will be at or even below
normals. Blended ensemble guidance shows some cooling on Sunday
but think this may be optimistic as hgts and pressure gradients
really do not change that much. If the current forecast
temperatures are correct the only areas that might need heat
advisories would be the mtns.

The high persists over the area both Monday and Tuesday. The
temperature differences will continue with the coasts sitting
near normal with a stubborn night through morning low cloud
pattern in place and the interior seeing well above normal temps
under cloud free skies.
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&&

.AVIATION...
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19/1753Z.

At 17Z at KLAX, the marine layer was 2500 feet deep. The top of
the inversion was at 4200 ft with a temperature of 17 deg C.

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

Moderate confidence in all other 18Z TAFs. Flight cat changes may
be off by +/- 1 hour this morning for airfields with low clouds
at start of fcst period, and +/- 3 hours tonight. Cig hgts may be
off by +/- 300 ft. There is a 30% chance of no cigs tonight into
Thu morning at KBUR and KVNY.

KLAX...Moderate confidence in TAF. There is a 20% chance of
BKN008 cigs from 05Z-12Z Thur. Any east wind component should be
less than 6 knots.

KBUR...Moderate confidence in TAF. There is a 30% chance of no
cigs tonight into Thu morning.
-- End Changed Discussion --

&&

.MARINE...19/853 AM.

For the Outer Waters, high confidence in current forecast. Small
Craft Advisory (SCA) winds are expected through Friday night.
Brief lulls in the winds during the mornings hours are possible.
Seas will be steep and choppy through Friday night. Conditions
are then expected to be below SCA levels Saturday through Sunday
night.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. SCA winds and choppy seas will
persist through tonight, and again Thursday afternoon and
evening. For Friday through Sunday night, winds and seas should
remain below SCA levels.

For the inner waters south of Point Conception, moderate to high
confidence in current forecast. For the western Santa Barbara
Channel, winds gusts will be at SCA levels each afternoon and
evening today and Thursday. Elsewhere and otherwise over the
southern inner waters, winds and seas should remain below SCA
levels through Sunday night.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
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CA...Wind Advisory remains in effect from 3 PM this afternoon to 3
      AM PDT Thursday for zones 349-351. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Thursday for
      zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 3
      AM PDT Thursday for zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Saturday for
      zones 670-673-676. (See LAXMWWLOX).
-- End Changed Discussion --

&&

$$

PUBLIC...Rorke/jld
AVIATION...Sirard
MARINE...Sirard/Schoenfeld
SYNOPSIS...jld

weather.gov/losangeles

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