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000
FXUS66 KLOX 230323
AFDLOX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
823 PM PDT Tue Aug 22 2017

.SYNOPSIS...
A weak trough over the Coastal Waters will bring overnight low
clouds to the coast and valleys through Thursday morning. As the
low moves east of the area, overnight low clouds will retreat to
coastal areas. As high pressure builds over the area, a warming
trend is expected Friday through the middle of next week. Very
warm temperatures are likely, with the peak heating on Monday and
Tuesday.

&&

.UPDATE...

There are some low clouds across the Central Coast and between
Catalina Island and Orange County. Max temps today were about the
same at the coast...a couple of degrees up over the
mtns...Antelope Vly and the interior Vlys. The biggest jump in
temps was across the vlys where there was 4 to 8 degrees of
warming.

Biggest issue tonight is the return of the low clouds. Its likely
that by sunrise all of the coasts will be covered in clouds but
there is a fair chc that the San Fernando Vly will be clear
through the morning.

Current forecast is in good shape and no updates are planned.

&&

.SHORT TERM...(TUE-FRI)

Models also show moisture filling in below the inversion base
south of Pt Conception tonight as well so better coverage overall
is expected by Wednesday morning. Along with this there is a 1-2mb
onshore trend. So in addition to an increase in low clouds
tomorrow most coast/valleys should be a degree or two cooler as
well for highs.

After that we should begin a slow warming trend through the rest
of the work week. Gradients trends weakly offshore each day
leading to a weaker onshore flow.

.LONG TERM...(SAT-TUE)

Little change or slight warming Saturday, then more significant
warming as we get into Sunday, Monday, and especially Tuesday
where light offshore flow could finally bring some of that inland
heat to the coast. Warmer valley spots should see triple digits by
Sunday and likely 105 or higher by Tuesday. Inland coastal areas
like downtown LA probably won`t see 90 until Monday or Tuesday but
still above normal by Sunday. Temps expected to keep on climbing
through most of next week as well, possibly leading to some heat
advisories and/or excessive heat warnings by as early as Tuesday.
Models still so far not showing any monsoon moisture with this
heat wave so thunderstorms remain out of the forecast.

&&

.AVIATION...

22/0000Z

AT 2345Z, the marine layer at KLAX was near 1500 feet deep. The
top of the inversion was 3600 feet with a temperature of 26 degrees
Celsius.

Good confidence in TAFs KSBA and south through 08Z. Then fairly
low confidence from 08Z to 13Z as timing of low cloud arrival
could be off by 2 hours. Lower confidence for coastal TAF sites
cloud dissipation as well with a 30 percent chc of no clearing.

Moderate confidence in Central coast TAFs timing may be off by +/-
1 hour.

KLAX...Good confidence through 08Z then low confidence. IFR cigs
could arrive any time from 08Z to 11Z. There is a 30 percent chc
of no afternoon clearing.
KBUR...high confidence through 08Z then low confidence. IFR cigs
could arrive any time between 10Z and 13Z. There is a 20 percent
chc of no cigs at all.

&&

.MARINE...

22/815 PM

Outer waters...good confidence in current forecast. Sub Small
Craft Advisory (SCA) conditions through Wednesday. SCA levels will
likely develop Thursday afternoon with building seas to around 7
ft into Saturday morning. There will be a small S swell mixed with
the W-NW swell at times.

Inner waters...good confidence in the current forecast. For the
waters north of Point Sal, winds and seas will remain below SCA
levels through Wednesday. On Thursday and Friday, SCA level winds
are likely each afternoon and evening with winds diminishing below
SCA levels on Saturday and Sunday. For the waters south of Point
Conception, winds and seas are expected to remain below SCA levels
through the weekend.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK...(FRI-TUE)
A significant heatwave could develop this upcoming weekend and
continue into early next week.

&&

$$

PUBLIC...MW/Rorke
AVIATION...Rorke
MARINE...Boldt/ASR
SYNOPSIS...Smith

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