738 
fxus66 klox 220314 
afdlox 


Southwest California area forecast discussion...updated 
National Weather Service Los Angeles/Oxnard California 
815 PM PDT sun Mar 21 2010 


Synopsis... 


Expect dry conditions to continue through at least midweek...with 
some cooling expected over the next few days. Some patchy low 
clouds overnight with more widespread low clouds across coast to 
foothills Monday night and Tuesday for areas south of Point Conception. 
Some warming expected on Wednesday as offshore flow kicks in. 


&& 


Short term (today-wed) 
temperatures were similar in most areas today...except much cooler across 
the interior valleys of slow County. Skies remained mostly cloudy as 
a high cirrus cloud shield persisted across much of the forecast 
area today. Highs across portions of the la coastal and valley 
regions were able to reach the lower 80s once again today. Temperatures 
should cool off a bit tomorrow as a stronger onshore flow will cool 
inland temperatures 3 to 6 degrees and a few degrees along the coast. 


At the upper levels...a closed low currently located around 700 
miles west of so cal will continue to move southeastward towards Baja California 
and remain well south of the County Warning Area as it pushes across northern Baja California on Tuesday 
and fills in. There will be very little effect from this low as it 
skirts to the south and east of the region. During the same time 
frame...another positive tilted inside slider will move in across 
Nevada and eastern cal. 


Behind this passing dry front...northerly winds will increase across 
the la/vtu County mountains Monday night as well as the offshore waters 
of the central coast. This will cause a couple things to occur. 
First...with the northerly winds expected to develop across la/vtu 
c0county mountains...some residual moisture will pile up against the northern 
slopes late Monday/early Tuesday morning bringing foggy conds to the 
Grapevine. Secondly...a healthy Catalina eddy will develop deepening 
the marine layer across la/vtu/sba counties. Expect low clouds to 
reach the valleys and coastal slopes of the foothills by early Tuesday 
morning. The marine layer could be as deep as 4500 feet S of Point 
Conception...while the central coast should remain mostly clear. 


Tuesday should be the coolest day of the week with partly to mostly 
cloudy conditions. One caveat with the deep marine layer...although 
the marine layer is expected to be widespread across the coast and 
valleys to the coastal slopes of la/vtu/sba counties...850mb winds 
will turn offshore by late morning...which could thin the marine 
layer by early afternoon as NAM-WRF suggests. By Tuesday night...upper 
ridge will rebuild briefly ahead of another trough moving towards 
northern cal. Surface grads will trend offshore with limited time for upper 
level support. This should help offshore flow to warm temperatures back up to 
above normal highs on Wednesday across coast and coastal valleys. At this 
time...only expecting sub Wind Advisory thresholds for the la/vtu 
County mountains highs should bounce back to the middle to upper 70s...and 
possibly around 80 in warmest spots of la/vtu counties. 


***From previous discussion*** 


Long term (thu-sun)...for the extended...12z models are not in the 
best agreement. However...no model indicates any significant threat 
of precipitation through Sunday. 


On Thursday...all models agree on flattening the upper ridge which 
will result in some noticeable cooling across the area. On Friday 
both the GFS and European model (ecmwf) move a trough across northern/central 
California with the European model (ecmwf) much sharper and slower with the trough. 
Either way...the impacts upon our area will be minimal and will go 
with a persistence forecast. For Saturday/Sunday...an upper level 
ridge will once again build over the area which will result in 
warmer temperatures for the area and continued dry weather. 


&& 


Aviation...21/2345z. 


Moderately high confidence for inland tafs...with lower confidence 
for coastal tafs due to stratus timing overnight. High clouds will 
continue to stream across the area overnight with mainly VFR conds. 
However...IFR ceilings should develop off la/vtu coastal areas with 
LIFR/IFR conds for ksmx after 09z. 30 percent chance that stratus 
could develop over ksbp as well and persist through 16z...also 40 
percent chance that ceilings could burnoff from 16z-18z for same coastal 
areas. 50 percent chance for LIFR.IFR ceilings/conds at kprb from 
10z-16z. 


Klax...just below moderate confidence for timing of IFR ceilings 
developing at lax. Put in 1/2sm fog for 9-13z but only 5o percent 
confident as stratus ceilings should be a tad higher than last night. 
Otherwise better confidence with overall taf. 


Kbur...high confidence in taf...except 40 percent chance of brief 
IFR ceilings between 10-14z. 




***Note*** 
the ASOS equipment at kbur...kvny...khhr...kcma...and koxr has a 
software error that may lead to incorrect cloud heights when there 
are two or more cloud layers present. Observations at kbur will be 
quality controlled 24 hours a day...observations at kvny will be 
quality controlled from 13z-07z...observations at koxr will be 
quality controlled from 15z-05z. Tafs for kvny and koxr will not be 
amended for ceilings during the time the observations are not monitored 
and there are two or more cloud layers present. 


&& 


Lox watches/warnings/advisories... 
gale watch (see laxmwwlox). 


&& 


$$ 


Public...Kaplan/Thompson 
aviation...Kaplan 


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