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Southwest California area forecast discussion 
National Weather Service Los Angeles/Oxnard California
910 PM PDT Wednesday Sep 17 2014

Synopsis...
other than some gusty sundowner winds across southern Santa Barbara
County...quiet weather is anticipated tonight. Low pressure will
develop Thursday and Friday along the West Coast...bringing cooler
temperatures and increasing coastal low clouds. For the weekend and
into early next week...high pressure will gradually build and result
in a gradual warming trend.

&&

Short term (tonight-sat)...there were some gusty west winds along the
immediate coast of vtu/l.A. Counties this evening...with gusty SW
winds in parts of the Antelope Valley. Gusty North Canyon winds developed
in the Santa Ynez range and S sba coast...with a Wind Advisory in
effect for the sba S coast through midnight. Otherwise...mostly clear
skies covered the forecast area this evening. A weakening cold front
was approaching the central coast this evening. Low clouds
associated with the dying front are expected to move into slo/sba
counties overnight along with patchy drizzle. Low clouds should also
develop S of Point Conception later tonight and affect the l.A.
County coast before moving up the coast and inland very late tonight
into Thursday morning. Elsewhere...mostly clear skies will prevail through
the night.

A rather sharp upper level trough over the east Pacific will move into northern
and central California on Thursday. An upper level low is forecast to develop off
the central California coast Thursday night then drift to a position near or just
SW of Point Conception on Friday. The upper low should drift NE and
inland some over southwestern California on Sat. It appears the main affect of the
upper low will be to deepen the marine layer with plenty of low
clouds for the coast and valleys night and morning hours...and possibly
even into the afternoon. Patchy drizzle can also be expected over
the coast and valleys Thursday night and Friday morning...although there may also
be patchy drizzle in some areas Friday night into Sat morning. A few
afternoon cumulus buildups cannot be ruled out over the mountains by Sat...but
at this time it appears the chances of any thunderstorms are less
than 10 percent as there will not be a whole lot of moisture with
the upper low and instability should be marginal at best for the
most part. A large impact of the upper low will be much cooler
temperatures in all areas...as highs fall to near normal to slightly
below normal Thursday through Sat...with the cooler of the three days on Friday.

***From previous discussion***

Long term (sun-wed)...models agree on the cutoff low lifting
northeast Sunday for additional warming and marine layer shrinkage.
The warming trend to continue through Tuesday with highs climbing
back to normal levels as early as Monday and possibly slightly above
Tuesday. For the latter half of next week the models have shifted
big time away from the huge 600+dm high over northern California to a rather deep
trough across the Pacific northwest. Even the 5 wave pattern has shifted to a
trough along the West Coast for late next week. Confidence still not
particularly high given the extremes in both solutions, but given
that the 12z European model (ecmwf) and GFS are both in remarkable agreement on this
change i'm inclined to go along with it. With this in mind most
areas should see a cooling trend beginning Wednesday and continuing
through the end of next week. It's a far cry from what looked like
an even hotter heat wave than what we just experienced and I would
not be terribly surprised to see the models flip back to that
solution.

&&

Aviation...17/2355z...generally moderate confidence in the 00z tafs
due to uncertainties with timing of low clouds tonight and Thursday for
all the coast and adjacent valley airfields. However...there is
generally hi confidence that low clouds and LIFR/IFR/MVFR conditions
will affect most of these airfields during the taf period. The onset
of low clouds will range from 03z this evening at ksmx to 17z Thursday at
ksba...although the lowest confidence for low clouds will be at ksba.
Also...the timing of the onset of the low clouds may be off
plus/minus 1-2 hours especially S of Point Conception. There is also
uncertainty to the timing of the low clouds scattering out Thursday
afternoon for most airfields which may be off plus/minus an hour or
two...but should linger through much the Thursday afternoon at koxr...klax
and klgb. Low level wind shear is possible at times tonight at ksba
due to gusty North Canyon winds in the vicinity. For kpmd and kwjf...hi
confidence in VFR conditions through Thursday...with gusty SW winds early
this evening and again by Thursday afternoon.

Klax...moderate confidence overall in the 00z taf due to
uncertainties with timing of low clouds late tonight and Thursday. The
low clouds with MVFR ceilings should develop around 10z then linger through
22z before moving back into the airfield by 03z Thursday evening. The
timing of the onset and dissipation of the low clouds may be off
plus/minus 1-2 hours. Otherwise...VFR conditions can be expected
this evening through late tonight and again late Thursday afternoon and
early evening. There is a 20 percent chance the low clouds may not
scatter out at all on Thursday.

Kbur...moderate confidence overall in the 00z taf due to
uncertainties with timing of low clouds late tonight and Thursday. The
low clouds with MVFR ceilings should develop around 12z then linger through
22z. The timing of the onset and dissipation of the low clouds may
be off plus/minus 1-2 hours. Otherwise...VFR conditions can be
expected this evening through late tonight and again late Thursday afternoon.

&&

Marine...17/830 PM
moderate to high confidence in current marine forecast. Advisory
level winds across much of the outer waters through late in the
week. The strongest winds will be near Point Conception during the
middle afternoon to early evening period. West to northwest winds have
increased across the western portion of pzz650-655 with short period
seas building due to the stronger winds. The Small Craft Advisory
for the outer waters has been extended over the near shore
waters...and the combination of gusty winds and choppy seas is
expected to continue through late tonight.

&&

Beaches...17/830 PM
long period southern hemisphere swells continue with contributions
from a couple of different storms. The elevated surf that resulted
from the southerly swells prompted issuance of a beach hazards
statement for higher surf and strong rip currents. The surf will
persist through Thursday and then begin to subside through
Friday...but the risk of rip currents will likely continue through
Friday afternoon.

&&

Lox watches/warnings/advisories...
Wind Advisory (see laxnpwlox).
Small Craft Advisory (see laxmwwlox).
Beach hazards statement (see laxcfwlox)
high rip current risk (see laxsrflox).

&&
$$

Public...sirard/mw
aviation...sirard
marine/beaches...Smith
synopsis...rat

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