Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
905 PM PDT Wednesday Oct 22 2014
High pressure aloft and weak offshore flow will result in slightly
above normal temperatures through the end of the week. A weakening
cold front will bring cooler weather for the weekend and a slight
chance of showers north of Point Conception on Saturday. Warming is
likely early next week following the passage of this system.
Short term (tonight-sat)...the marine inversion at lax early this
evening was around 900 feet deep. Marine layer clouds were absent over
the coastal waters this evening...with fair skies and a few hi
clouds at times over the forecast area. Little change is expected
overnight. However...a weak eddy is expected to develop over the
socal bight later tonight which may help to develop a few low clouds
over the coastal waters mainly S of the Palos Verdes Peninsula...
with some low clouds possibly affecting the immediate l.A. County
coast especially around Long Beach by daybreak Thursday.
An upper level ridge of high pressure will linger over Southern California on
Thursday...then weaken slightly on Friday. A large upper level trough over the
east Pacific is expected to approach mainly central California through the day on Sat.
At the same time...a weak upper level disturbance is forecast to
possibly move into the area from the southwest. Weak offshore flow
night and morning hours can be expected Thursday morning...and again Thursday
night into Friday morning...but mainly over slo/sba counties. This will
limit any marine layer clouds over the coastal areas...except for
the southern l.A. County coast. For Friday night and Sat...some
increase in marine layer clouds can be expected...especially along
the central coast. Cloudiness and a slight chance of showers from a
dying cold front is expected to move into slo/sba counties by Sat as
well. The 00z NAM is forecasting decent moisture between 850 mb and
700 mb moving into the area from the S and SW associated with the
upper disturbance...while the 18z GFS shunts this moisture well S
and east of the region. This moisture could result in some showers over
parts of the region...but for now will wait for later model runs to
make any changes to the forecast. Overall...though...it looks like
mostly clear skies should prevail through Friday...with partly cloudy
skies for Sat. Temperatures across the region are forecast to turn slightly
warmer the next couple of days and remain several degrees above
normal. It looks like temperatures will cool significantly over slo/sba
counties on Sat...with not as much cooling elsewhere.
***From previous discussion***
Long term (sun-wed)...the cooling continues on Sunday to make it
the coolest day of the period. Highs will be around 5 to 10 degrees
below normal. Skies will be mostly clear outside of some morning
stratus possible over coastal la and vtu counties.
After Sunday...the trough moves east and high pressure builds over
the area again for the first half of next week. Some disagreement
between the GFS and European model (ecmwf) as far as how much ridging will occur. The
GFS is much stronger with the ridging by Wednesday while the ec
actually puts a weak progressive trough along the West Coast. The
GFS has shown a little better run to run consistency so far. In
general forecast reflects a gradual warmup through midweek but
nothing too wild.
Aviation...22/2355z...the marine layer at klax at 2300z was 700
feet deep and the inversion top was at 2100 feet with a temperature
of 24 degrees c.
High confidence in the 00z tafs with generally VFR conditions
expected at nearly all the airfields through Thursday. Only exceptions are
at klgb where a brief period of IFR ceilings will be possible from about
11z-15z Thursday...with a 50-60 percent chance of this occurring...and at
klax where MVFR visibilities are possible 12z-16z. Otherwise... VFR
conditions can also be expected at these airfields through Thursday.
Klax...hi confidence in the 00z taf with mostly VFR conditions
expected through Thursday evening...except for a brief period of MVFR visibilities
12z-16z. There is also a 10-20 percent chance of IFR ceilings late
tonight and early Thursday.
Kbur...hi confidence in the 00s taf with VFR conditions expected
through Thursday afternoon.
For the outer waters...high confidence in Small Craft Advisory level
winds continuing through tonight...and moderate confidence that the
small craft winds will continue through Thursday evening. For Friday
through Saturday...winds are anticipated to remain below Small Craft
Advisory levels before increasing again on Sunday.
For the inner waters...winds are anticipated to remain below Small
Craft Advisory levels through Saturday. Winds will become resurgent
on Sunday with small craft advisories again possible.
Small Craft Advisory (see laxmwwlox).
High rip current risk (see laxsrflox).