Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
920 PM PDT Thursday Jul 31 2014
an upper level high east of the region will keep temperatures above
normal through the weekend. Night and morning low clouds will affect
much of the coast line through the period. Monsoonal moisture will
bring a slight chance of thunderstorms to the mountains and deserts
on Sunday...otherwise dry conditions are expected.
Short term (tonight-sun)...the marine inversion remained rather
shallow at lax this evening at around 700 feet. Low clouds and fog
were along the central coast and have started to push inland which
should continue overnight and into the Santa Ynez Valley. S of Point
Conception...an eddy is forecast to develop overnight which should
help to expand low clouds to some coastal areas. Otherwise...mostly
clear skies will prevail across the forecast area through tonight.
Gusty SW winds in the Antelope Valley will diminish overnight.
Upper level ridging will persist over the forecast area through Friday
night then it looks like an inverted upper level trough will approach
the area from the southeast on Sat. This system will linger over southeastern California
through sun. The upper level system will bring a surge of monsoonal
moisture into southwestern California especially Sat night and sun. The 00z NAM
forecasts extensive 600 mb moisture over l.A. County into portions
of vtu County Sat night and sun. There does appear to be a remote
chance of an afternoon thunderstorm in the vtu/l.A. County mountains and
Antelope Valley on Sat...generally 10 percent or less. A slight chance
of thunderstorms is expected for these areas Sun afternoon and
evening. The forecast will be a bit tricky on sun depending on where
the upper trough sets up and how much sunshine the area receives. If
the NAM is correct...there may be enough cloud cover on sun to
inhibit convection. There is also the possibility that showers and
any high-based thunderstorms could drift to the coast and valleys on
sun. For now will not change the forecast for sun for the coast and
valleys pending additional model runs. Some marine layer clouds can be
expected night and morning hours for the central coast and mainly
l.A. County coast...otherwise mostly clear skies should prevail through
Sat then become partly cloudy Sat night and sun...although as mentioned
above there could be mostly cloudy skies for the eastern portions of
the forecast area on sun. Temperatures are forecast to remain several
degrees above normal for many areas through sun although highs will cool
off a couple of degrees each day.
***From previous discussion***
Long term (mon-thu)...if Sunday ends up being active then it's
likely that Monday will have some thunderstorms over the mountains and
deserts, though moisture is definitely on the decrease by that time.
Keeping it dry for now. Otherwise, not much change in
heights/thicknesses through Wednesday with a weak trough lingering just off
the coast. By Thursday the trough is expected to push inland leading to a
few degrees of cooling most areas.
Aviation...31/2355z...generally hi confidence in the 00z tafs...
although moderate confidence at best for low clouds and IFR/MVFR
conditions at koxr...klax and klgb late tonight into Friday morning.
Low clouds and IFR/LIFR conditions are likely to affect ksbp and
ksmx this evening through later Friday morning. Otherwise...VFR conditions
can be expected at the airfields through Friday. Gusty west to SW winds at
kpmd and kwjf this evening will diminish tonight then increase again
Klax...generally hi confidence in the 00z taf...although there is a 60
percent chance of low clouds and IFR conditions 11z-17z Friday.
Otherwise...VFR conditions can be expected for the most part through
Kbur...hi confidence in the 00z taf with VFR conditions expected
through Friday afternoon.
Marine...31/830 PM PDT...
local gusts to 25 knots are expected over pzz655 through late this
evening...otherwise Small Craft Advisory conditions are no longer
expected in that portion of the waters. Gusty northwest winds will persist
over the southern outer waters through late tonight. Little change
is expected in the forecast through the weekend...with northwest winds
increasing over the outer waters each afternoon to evening period
through Sunday. The strongest winds will be over pzz673-676...with
somewhat lighter speeds over pzz670. Mainly light to locally
moderate winds are also expected for all nearshore waters through
Small Craft Advisory (see laxmwwlox).