Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
440 PM PST Sat Dec 21 2013
..updated aviation discussion...
Synopsis...a large ridge of high pressure will prevail through the
end of next week...resulting in generally fair weather. A warming
trend is expected through early next week...with above normal
temperatures continuing through the end of the week. Cooler weather
is possible by next weekend...as a low pressure system may approach
the West Coast.
Short term (today-tue)...guidance initialized a surface ridge of
high pressure over the eastern Pacific and trough of low pressure
near shore with strong gradient level north winds centered over the
offshore waters reasonably well. Guidance was consistent with
previous runs and the offshore winds will diminish as the surface
ridge shifts northeast and builds inland overnight. In the meantime
the nearshore surface trough will persist through the afternoon then
gradually weaken overnight. A weak offshore pressure gradient will
then prevail Sunday and through the remainder of the period as high
pressure persists over the Great Basin.
A mean long wave ridge of high pressure over the central Pacific is
expected to shift northeast over the eastern Pacific Sunday through
Tuesday. The upper level cloud field northeast of the Hawaiian
islands this afternoon will move through the ridge and over the area
Tuesday. In the meantime the broken low cloud field over the la
basin and off the central coast will mix out or remain offshore
within the drying offshore winds. The temperature trend was mixed
this afternoon and differed by plus 5 to 10 degrees over the north
and inland portions of the area and by minus 2 to 5 degrees over the
southern coastal portion of the area from yesterday at this time.
And temperatures were 5 degrees above seasonal in the desert and 5
to 10 degrees below normal elsewhere. A warming trend is expected
Sunday through Tuesday and temperatures will likely be 5 to 10
degrees above normal over the entire area by Monday.
Long term (wed-sat)...will continue dry through the period. A long
wave ridge is expected to persist over the area and upstream. There
is a chance the ridge will weaken and a trough will shift east over
the eastern Pacific Friday through Saturday. An overcast to broken
upper level cloud field may then move ashore Saturday and a broken
low level cloud field may develop over the bight Friday night
through Saturday morning. Temperatures may differ by one or two
degrees Wednesday through Friday and then differ by minus 2 to 5
degrees over the entire area Saturday.
Overall high confidence in 00z tafs...with VFR conditions expected
for most sites...with the exception of the l.A. Coastal basin.
However...there is a 30% chance that the l.A. Coastal sites will
remain VFR through the period.
Klax...high confidence in 00z taf...expecting VFR conds through the
next 24 hour period. However there will be high confidence for MVFR
ceilings to develop from 00z to 10z as well.
Kbur...high confidence in 00z taf...with VFR conditions expected
throughout the 24 hour forecast period.
Small Craft Advisory (see laxmwwlox).
Coastal beach hazard (see laxcfwlox).