Scientific Forecaster Discussion
Southwest California area forecast discussion...updated
National Weather Service Los Angeles/Oxnard California
320 PM PST sun Nov 29 2015
..updated aviation discussion...
A warming trend is expected through middle-week as high pressure builds
aloft and offshore flow continues. Low pressure aloft is expected to
pass to the north Thursday...supporting the chance of showers to the
north of Point Conception and seasonable temperatures heading into
Short term (today-wed)...overall...12z models in good synoptic
agreement through the period. At upper levels...ridge will gradually
build along the West Coast...peaking in strength on Wednesday. Near
the surface...weak offshore flow will continue.
Forecast-wise...nothing too remarkable is anticipated. With the
upper ridge building and weak offshore flow...afternoon temperatures
will be on the upswing...peaking on Wednesday with most areas
several degrees above seasonal normals. As for overnight lows..the
air mass will gradually moderate and sub-freezing temperatures will
be less widespread. There will be some areas below freezing
tonight...but do not anticipate anything widespread enough to need
any frost/freeze products. As for winds...there is limited upper
level support...so no widespread advisory level northeasterly winds
are expected through Wednesday.
Long term (thu-sun)...overall...12z models continue to exhibit good
synoptic agreement through the period. At upper levels...trough will
move across the West Coast on Thursday then a ridge will build over
the area Friday through the weekend. Near the surface...flow turns
weakly onshore on Thursday...then back to a north and northeast
offshore flow through the weekend.
Forecast-wise...main issue is Thursday as the upper trough moves
across the West Coast. Models sweep a weak front across the area
Thursday afternoon/evening with the system losing steam as it rounds
Point Conception. With the afternoon forecast...have tweaked probability of precipitation a
bit...but still generally kept low chance probability of precipitation for slo/sba counties
slight chance for vtu County then unmentionable probability of precipitation for lax
County. Any rain that falls will be light and end by Friday morning.
On Friday...northerly winds will develop behind the front and there
could be some advisory-level winds in the usual north wind-prone
spots. The northerly flow will bring in some colder air...so
temperatures on Friday will be the coolest of the next seven days.
For Friday night through Sunday...the flow turns northeasterly. The
northeast flow looks to be on the weak side...but still a bit early
to get a good handle on potential for any advisory-level winds.
However the combo the upper ridge and offshore flow will keep the
area dry and bring warmer temperatures.
At 2320z...there was no marine layer inversion at klax.
High confidence in 00z tafs with VFR conditions expected through the
Klax and kbur...high confidence in ceiling and visibility unlimited tafs.
Locally gusty east winds continue in the Santa Barbara Channel with
local gusts to 20 knots near Santa Cruz Island. These winds are
expected to gradually decrease through the day. Otherwise...light
winds are expected through middle week. A large long period northwest
swell will begin to move into the waters tonight into
Monday...peaking Tuesday around 10 feet at 15 seconds.
high surf advisory (see laxcfwlox).