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Southwest California area forecast discussion 
National Weather Service Los Angeles/Oxnard California
130 PM PDT Thursday Jul 30 2015


There is a chance of thunderstorms for the interior mountains and
deserts through Friday. The thunderstorm threat will be confined to
the Los Angeles and Ventura County mountains and adjacent deserts on
Saturday. By Monday stabilizing southwest flow aloft will end the
threat of thunderstorms with a return to seasonal temperatures.


Short term (today-sun)...

A weak vorticity maximum embedded in southeast monsoonal flow aloft continues to
move northwestward through the County Warning Area this afternoon. This feature is
currently located over Ventura County and will move north of slo
County after midnight tonight. Earlier this morning there were some
scattered showers over la and Ventura County coastal/valley areas
that were associated with this vorticity. Thunderstorm activity this
afternoon has shifted to the mountains and other interior areas. The
strongest storm so far occurred over northwest Ventura County and eastern
sba County in the mountains...where there was plenty of sun this
morning to allow for surface heating. A Flash Flood Warning was
issued for this storm. Seeing some clearing for southern portions of
the County Warning Area early this afternoon...which should lead to an increase in T-
storms in la and Ventura County as well...focused mainly over the
mountains...desert and some interior valleys. Flash flooding will
continue to be a threat for these areas...where a Flash Flood Watch
remains in effect through this evening.

Leaning towards removing T-storms for most coastal and some valley
areas later this afternoon and this evening...depending on how the
rest of the afternoon GOES. Thinking that most of the T-storm
activity for these areas was or will be associated with the middle-
level vorticity maximum...which will be north of Ventura County by 00z. This
will be a last minute decision.

A slight chance of T-storms will continue into the late evening
hours for the mountains and interior areas...before diminishing late
tonight. Thunderstorm activity will resume for these areas late
tomorrow morning through tomorrow evening...with the focus of the
activity over the mountains and Antelope Valley. Without a kicker
and a more south-southeast steering flow...not expecting any T-storms for the
coast and most valley areas tomorrow.

The areal covereage of T-storms on Saturday was reduced to only have
a slight chance of T-storms over the vta/la mountains and the
Antelope Valley. With flow aloft starting to shift to the SW on
Saturday...moisture and instability will continue to decrease...with
most of the instability focused over the vta/la mountains. The
drying trend will continue on Sunday as SW flow becomes established
aloft...but there could still be enough lingering instability to
warrant the slight chance of T-storms for the eastern san Gabriels
and Antelope Valley.

Temperature trends for tomorrow will be a little tricky due to all
of the clouds we had earlier today...however Friday and Saturday
will be slightly cooler overall as height/thickness and 850/950
temperatures fall slightly. Slight warming trend may begin on Sunday as the
ridge over New Mexico starts to build...resulting in slight
height/thickness rises over SW California. Also introduced some low
clouds in southern la County on Sunday morning as the marine layer
may start to re-develop with SW flow aloft due to a weak upper-low
off the coast.

Long term (mon-thu)...

Overall not a very exciting weather pattern next week with a
persistent ridge over the interior western U.S. And a trough off the
West Coast. The trough will bring a better chance for marine layer
stratus for most coastal areas next week. No significant temperature
trends in the forecast next week as there is some slight
disagreement in the models. GFS builds the ridge more
agressively...which would result in a warming trend for interior
areas...while the European model (ecmwf) keeps the ridge relatively flat. Current
forecast has temperatures generally near normal next week.



Marine layer around 010 this morning.

All airports in VFR this morning. Moderately confident that showers
and thunderstorm chances will decrease over the coastal and valley
locations this afternoon. Kwjf kpmd and kprb have a 20-30 percent
chance of a thunderstorm this afternoon and evening...possibly
lingering through most of Friday. Stratus will be greatly restricted
due to nearby convection...but expecting a few random patches to be
around some coastal airports tonight into Friday morning. Weaker
than usual winds will prevail today...except for possible gusty
winds near any thunderstorms.

Klax...moderate confidence in VFR through Friday...with a 30 percent
chance of IFR ceilings forming becoming 03 and 17z. Main threat of
convection has shifted well inland...but there still is a 10 percent
chance of a tsrm into this evening.

Kbur...high confidence in VFR through Friday. Main threat of
convection has shifted well inland...but there still is a 10 percent
chance of a tsrm into this evening.


Marine...29/900 am.
Unstable air is pushing from south to north today with a 20 percent
chance of a thunderstorm forming over the coastal waters. Moderate
to high confidence of no thunderstorms expected after this evening.
30 percent change of low grade Small Craft Advisory winds south of
Point Conception tonight and Friday night. Small Craft Advisory
winds likely over the weekend over the outer waters...with choppy
conditions over the inner waters.


Lox watches/warnings/advisories...
Flood Watch (see laxffalox).
Marine weather statement (see laxmwslox).





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