Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
215 PM PDT Monday may 25 2015
Synopsis...persistent low pressure over the western United States
will maintain below normal temperatures through middle week with ample
night through morning clouds. High pressure will build over
California Thursday through the weekend bringing a warming trend
away from the coast. Coastal areas should continue to see low clouds
and fog...and high temperatures which will edge up a bit.
Short term (tonight-thu)...
weak upper level trough of low pressure over northern and central
California has helped to maintain strong onshore flow across Southern
California. Marine layer depth ranged between 3,000 and 4,000 feet
across the district today. This deep marine layer combined with daytime heating
allowed considerable stratocumuluscloud development today for areas south
of Point Conception. Satellite imagery showing decreasing cloud coverage
trend across Ventura County but still mostly cloudy across portions of
the la basin. Also...some afternoon buildups over the local mountains due to some
residual moisture and instability from daytime heating. The strong onshore
flow and cloud coverage helping to keep temperatures below normal once again.
Marine layer clouds expected to spread into most coastal/valley areas
overnight into Tuesday morning. Some higher level clouds in advance of a
weak upper level low pressure system will also begin to stream across the
district tonight into Tuesday. Little change into Wednesday...then marine
layer depth expected to shrink on Thursday as an upper level ridge of high
pressure begins to build off the coast. Temperatures expected to gradually
edge upward the next couple of days...then a more noticeable warmup on
Thursday as warmest valleys climb into the middle 80s and Antelope Valley
reaches 90 degrees.
Long term (fri-mon)...the upper level ridge of high pressure is
expected to strengthen and become more centered over southwest
California Friday into Saturday. These will likely be the warmest days of
the week...with warmest valleys and mountains climbing to around 90 degrees
and Antelope Valley climbing into the middle 90s. During this time...we will continue
to see the marine layer depth shrink. The ridge axis is then
expected to shift eastward of the area Sunday into Monday...with gradual
cooling trend to begin.
An upper ridge will amplify in the eastern
Pacific Thursday...then the ridge will edge into the West Coast on Friday.
The marine layer will shrink in depth...and there will be a
reduction in night/morning low clouds...especially in the valleys. Maximum
temperatures will be up a few degrees both Thursday and Friday...with temperatures above
normal in most areas on Friday. The ridge axis will move east of the
region over the weekend...but heights will remain rather high. Do
not expect much change in maximum temperatures on Sat...then there could be
slight cooling...especially west of the mountains on Sunday.
At 17z at klax... the inversion was 1550 feet deep. The top of the
inversion was at 4900 feet with a temperature of 13 degrees celsius.
Overall... moderate confidence in the 18z tafs. The marine
intrusion will continue along portions of the coast and well into
adjacent valleys through midday. It will diminish to just off the
coast this afternoon though the taf timing may be off by an hour or
so. The intrusion will return this evening and will develop similar
to last night and this morning. Otherwise and elsewhere VFR
conditions will prevail.
Klax... moderate confidence in the 18z taf. The marine intrusion
will continue through midday then diminish to just off the coast
this afternoon though the taf timing may be off by an hour or so.
The intrusion will return this evening and will develop similar to
last night and this morning. Otherwise VFR conditions will prevail.
Kbur... moderate confidence in the 18z taf. The marine intrusion
will continue through midday then diminish this afternoon though the
taf timing may be off by an hour or so. The intrusion will return
this evening and will develop similar to last night and this
morning. Otherwise VFR conditions will prevail.
Marine... 25/200 PM
Moderate to high confidence in the marine forecast. Northwesterly
wind gusts to 25 knots will periodically flow across the western
portion of the Santa Barbara Channel and the nearshore waters
between Point Piedras Blancas and Point Sal during the next couple
of days. Otherwise conditions across the coastal waters will remain
below advisory levels through midday Wednesday. Winds will
strengthen on Wednesday and small craft advisories may be needed for
the outer waters Wednesday night and Thursday.
A southerly swell with a long period will bring moderate surf to
south facing beaches of Los Angeles and Ventura counties through at
least tonight. In addition...there will be a high risk of rip
dangerous currents through Tuesday.
beach hazards statement (see laxcfwlox).
High rip current risk (see laxsrflox).