Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
215 PM PDT Friday may 29 2015
Above normal temperatures are expected for inland areas through the
weekend as high pressure moves overhead. Temperatures will return to
near normal next week as a moisture starved frontal system
approaches late Sunday...then a broad trough of low pressure
develops. There is a good chance of night through morning low clouds
and fog for coastal areas and some valley areas through next week.
Short term (tonight-mon)...upper level high pressure system building
over Southern California through Saturday...with moderate onshore flow
continuing near the surface. While low clouds burned off quickly this
morning across inland areas...they have lingered across some immediate
coastal areas this afternoon due to strengthening marine inversion.
As expected...temperatures warming inland this afternoon...with warmest
valleys already reaching 90 degrees...and the Antelope Valley climbing
well into the 90s.
Marine layer depth expected to shrink over the weekend...likely in the
1000 to 1500 foot range. As a result...expecting low clouds and fog to
mainly be confined to the coastal plain and some of the lower valleys
elevations. Saturday looks to be the warmest day of the week across much
of the region as 950 mb temperatures and thicknesses peak across inland
areas. By Sunday...upper level ridge axis begins to shift slightly
eastward as another upper low approaches the California coast. Still
another warm day expected on Sunday...but temperatures down 2-3 degrees
for most inland areas. Since marine inversion will remain low and strong
through the weekend...low clouds will likely linger across some
immediate coastal areas keeping temperatures on the cooler side.
With this in mind...there will be a strong temperature gradient between
coastal and valley areas through the weekend. Upper level trough expected
to move through area on Monday...bringing stronger onshore flow and a
deeper marine layer. More noticeable cooling expected across the region
on Monday as well as gusty onshore winds across the mountains and Antelope Valley.
Long term (tue-fri)...both the GFS and European model (ecmwf) are indicating a
persistent upper trough pattern across California through most of
the week. Night and morning low clouds and fog will be prevalent
across most coastal and valley areas along with cooler than normal
temperatures through the period. Not expecting any precipitation...but
cant rule out some patchy drizzle during night and morning hours.
Breezy conditions continuing across mountains and deserts during
extended period due to strengthening onshore flow.
At 1700z the marine layer depth at klax was around 2300 feet deep. The
top of the inversion was around 3900 feet with a temperature of 22
Moderate confidence in 18z tafs...with low MVFR conds at most
coastal locations...except IFR at ksba. Expect slow burnoff for
portions of the central coast and near pt Conception southeastward to koxr
this afternoon. Similar low cloud pattern expected tonight into Sat
morning...although at this time not expecting low clouds in the l.A.
Valleys. However...there is a 30% chance that this will occur.
Klax...moderate confidence in 18z taf. Expect haze to linger through
20z as low clouds remain nearby...with a 10% chance MVFR ceilings will
return periodically through 22z. For the overnight period...expect
low MVFR/IFR ceilings. IFR conds could persist longer than forecast.
Kbur...moderate confidence in the 18z taf. VFR conds expected at
least through late this evening. There is a 30% chance that low
clouds will bring IFR conds to the site after 09z.
for the outer waters...moderate confidence that northwest Small Craft Advisory winds
will continue through tonight but there is a 30% chance the gusts
will subside this evening. For the weekend northwest winds expected
to be generally 10 to 20 knots over the outer waters...increasing to
Small Craft Advisory levels late Monday through Wednesday.
Across the inner waters...high confidence winds will remain below
Small Craft Advisory levels through Monday.
Small Craft Advisory (see laxmwwlox).