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Southwest California area forecast discussion 
National Weather Service Los Angeles/Oxnard California
1100 PM PDT Wednesday may 27 2015

New aviation discussion

Synopsis...

Building high pressure will result in a warming trend and a
shrinking marine layer into the weekend. Above normal temperatures
are expected for inland areas Friday through Sunday. A moisture
starved frontal system will approach the area by late
Sunday...bringing slightly cooler weather early next week.

&&

Short term (tonight-sat)...generally quiet weather across the forecast
area early this evening. Mostly clear skies prevailed for most
areas...although there were patchy low clouds along the sba County
central coast and from Santa Catalina Island to Palos verdes. The
low clouds are expected to expand along all coastal areas overnight
and move inland to the adjacent valleys...with mostly clear skies
elsewhere. Gusty S to west winds from the l.A. County mountains to the
Antelope Valley this evening will diminish overnight.

An upper level ridge just off the California coast this evening is forecast
to build into the area Thursday through Friday...then weaken slightly but
remain over Southern California through Sat. The may gray pattern will continue for
most coastal areas into some of the adjacent valleys through Friday...with
night and morning low clouds and fog. The marine inversion should
lower during the period...with low clouds confined mostly to the
coastal plain by Friday night into Sat morning. Otherwise...mostly
clear skies will prevail across the region. Breezy onshore winds can
be expected each afternoon and early evening during the period...
although gusty winds are expected in the Antelope Valley. With the upper
level ridge lowering the marine inversion...temperatures away from the
coast will warm up nicely. Highs are forecast to be near normal to
slightly above normal on Thursday...then warm inland to well above normal
Friday and Sat...with highs in the lower 90s for the warmest valleys.
Highs for the immediate coast will remain near normal for the most
part.

***From previous discussion***

Long term (sun-wed)...temperatures will peak Saturday before the ridge
weakens and shifts east as a new trough approaches northern California and the Pacific
northwest. Main influence locally will be the usual increasing marine layer
coverage, slower clearing, and cooler temperatures. Some recovery in temperatures
by around middle week as weak ridging develops again.

&&

Aviation...

28/0600z

At 0544z the marine layer depth at klax was around 1600 feet deep. The
top of the inversion was near 3400 feet with a temperature of 18
degrees celsius.

High confidence that stratus will affect all coast and valley tafs by
14z. Lower confidence in exact timing of arrival of low clouds.
North of Point Conception only fair confidence in MVFR ceiling height forecast
with a 30 percent chance of IFR ceilings. Good confidence in IFR forecast north
of Point Conception. Fair confidence in burn off time but 30 percent
chance forecast of scattered conds is off by +/- one hour.

Klax...good confidence in ceilings arriving by 12z but lower confidence
in exactly when. A 30 percent chance of a 21z burn off and a 20 percent
chance of 5sm haze conds at the terminal from 16z-23z.

Kbur...fair confidence in taf. There is a 30 percent chance of ceilings
arriving at 13z. There is a 30 percent chance that ceilings will be
ovc008 when they arrive. A 20 percent chance of a 19z transition to VFR
conds.

&&

Marine...

27/830 PM

Outer waters... expect north winds generally 10 to 20 knots over the
outer zones...with isolated gusts to 25 knots. Moderate confidence
that gusts will remain isolated this evening through around
midnight. There will be a better chance of Small Craft Advisory conditions over the
outer waters Thursday afternoon and evening as northwest winds
increase due to building high pressure to the northwest.

Inner waters...winds are expected to remain well below Small Craft
Advisory levels through Saturday...except for the western portion of
the Santa Barbara Channel where gusts to 20 knots are expected this
evening.

&&

Lox watches/warnings/advisories...
none

&&

$$

Public...sirard/mw
aviation...sirard
marine...Smith/sirard
synopsis...sukup

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