Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
935 PM PST Monday Nov 30 2015
..updated aviation discussion...
Continued warming is expected through middle-week as high pressure
builds aloft and offshore flow continues. Low pressure aloft will
pass to the north Thursday supporting a brief cool down and the
chance of showers to the north of Point Conception. Warm and dry
conditions are expected again this weekend as offshore flow returns.
Nearby low pressure aloft may bring showers late Sunday.
Short term (today-wed)...skies were mostly clear south of Santa
Barbara County this evening. The tail end of a weakening cold front
was moving across slo County. National Weather Service Doppler radar indicated some light
showers likely not reaching the ground just across the most northwest
portion of slo County...north of Cambria. A few foothills could get
a spritz over the next few hours...but not expecting any measurable
rainfall. Some clouds will linger through late this evening...but
offshore flow will strengthen slightly off the san Lucia mountains
and keep skies mostly clear late tonight into Tuesday. A few stray
clouds from the decaying front could push across Ventura and l.A.
Counties overnight...but should remain mostly clear. High
temperatures were just about the same in most locations
today...except some marginal warming across the mountains were
As is typical this time of year...the Antelope Valley will
experience sub-freezing temperatures in the upper teens once again tonight
into Tuesday morning...while the interior valleys of slo and sba
counties will lower into the middle to upper 20s. These areas have
already had two hard freezes...therefore you will not be seeing any
freeze products issued through the remainder of the fall/winter
season. However...Ojai Valley will experience freezing or near
freezing conditions along with some San Fernando Valley locations
located in the SW portion...including Woodland Hills,
Calabasas,Agoura Hills and Westlake Village.
Behind the upper trough and frontal passage...high pressure aloft
will build in over southern and central California tonight into
Tuesday. There should be enough light offshore winds across the
central coast tonight to keep most areas above frost thresholds.
There will be a few wind protected areas that could see temperatures
lower to just above freezing.
No changes to the forecast expected tonight. There will continue to
be weak offshore flow across the usual wind prone areas of Los
Angeles and Ventura counties over the next few days. Strongest Santa
Ana winds will occur early Wednesday morning as a strong surface
high sets up across the Great Basin. This will cause the lax-dag
surface gradient to strengthen to over -5.5 New Brunswick Wednesday
morning.Atthis time...not expecting wind advisories for the usual
wind prone areas but will monitor. Some additional warming for coast
and coastal valleys is expected both Tuesday and Wednesday. High temperatures will be
in the 70s by Wednesday...with cooler conditions across the interior
Looking ahead to next Thursday... latest 00z NAM and 18z GFS have
backed off a little with the southward progression of the next storm
system Thursday afternoon through Friday morning. Looks like the
majority of rain will occur north of Point Conception....which is not
much at all. Earlier models showed the possibility of some showers
holding together once it reached Point Conception. Latest run...not
so much. A strong surface low setting up over northern California with
this next system should help to cause gusty southerly winds ahead of
the approaching front for areas north of Point Conception.
***From previous discussion***
There will continue to be light offshore winds affecting the usual
wind prone areas of Los Angeles and Ventura counties tonight through
Tuesday evening. Lax-dag surface gradients are expected to remain
offshore this afternoon and then down to -3.5 mb early Tuesday
morning. This will continue to cause light offshore winds to occur
and additional warming across coast and coastal valleys on Tuesday
to more normal readings for this time of year. By Tuesday night into
Wednesday...a cold punch behind an exiting cold front moves into the
Great Basin. In turn...stronger surface high pressure to around 1032
mb builds into northern Nevada. This stronger pressure gradient and
cooler air advection into the High Desert will bolster up Santa Ana
winds a bit. At this time it looks like it will be just below Wind
Advisory thresholds for Wednesday morning...but winds will be more
widespread and should push all the way to the coast. Expect high
temperatures to reach the middle 70s across most coast and coastal valleys in
la/vtu counties. With cooler temperatures expected across the interior
areas...which is typical with this type of offshore pattern.
Long term (thu-sun)...the positive tilted ridge axis that will be
over socal into Idaho will be short lived as a rather strong upper
low begins to dig south as it strengthens. The trough axis becomes
negatively tilted as it approaches the northern half of California.
A strong surface low associated with the trough will develop just
off the coast of nocal by Thursday afternoon. Expect gusty southerly
winds ahead of the approaching trough for areas north of Point
Conception...especially across the coastal waters and slo County. At
this time...best chance of precipitation will occur for areas north of
Point Conception...with a slight chance of showers across the sba
South Coast and adjacent valleys and northern mountain slopes going into
Friday. Snow levels will begin quite high...over 7500 feet...but as
the trough moves through...snow levels should lower to around 5000
feet affecting the northern slopes of the Ventura and western la County
mountains with some light snow fall accumulations.
Best cooling on Thursday will occur for areas north of Point Conception
and all coastal areas as onshore flow kicks in ahead of the trough.
Widespread cooling will continue into Friday as the trough and
associated cold front moves quickly through the region. Another
ridge axis from socal into the Great Basin will develop behind the
exiting trough for Sat and Sunday. Sundowner winds are possible on
Friday with a return of Santa Ana winds by Saturday morning and once
again Sunday morning. Expect some warming across the la/vtu coast
and coastal valleys with offshore winds...but highs should remain in
the lower to middle 70s. Another upper trough could bring some showers
to areas north of Point Conception by Monday.
At 5000z...there was no marine layer inversion at klax.
High confidence in 06z tafs with VFR conditions expected through the
Klax and kbur...high confidence in 06z tafs.
Light winds are expected through middle week. A large long period
northwest swell will continue into the waters...peaking Tuesday
around 10 feet at 15 seconds. Another storm system will approach the
central coast on Thursday. Gusty southerly winds ahead of the front
will likely reach Small Craft Advisory thresholds. 30 percent chance
that gale watches might be needed for coastal waters north of Point
freeze warning (see laxnpwlox).
Frost advisory (see laxnpwlox).
High surf advisory (see laxcfwlox).