967 
fxus66 klox 191318 
afdlox 


Southwest California area forecast discussion...updated 
National Weather Service Los Angeles/Oxnard California 
615 am PDT Friday Mar 19 2010 


..updated aviation discussion... 


Synopsis... 


Dry weather is expected through next week. Gusty northeast winds 
will affect portions over the area this morning...with patchy 
morning low clouds and fog along the coast. Temperatures will 
increase through the weekend as high pressure builds over the 
area...cool down Monday and Tuesday as a trough moves through...then 
warm again through the end of the week. 


&& 


Short term (today-sun)... 
the rather strong coastal eddy that formed last evening is quickly 
eroding away as north to northeast winds increase over the area. The 
marine layer started out around 1500 feet last night and has been 
squashed down to around 500 feet...producing some patchy dense fog 
along the Ventura coast. Expect all clouds to clear out shortly 
after sunrise. 


Current VAD wind profile from local radars shows northeast to east 
winds 15 to 25 kts over the area...and some mountain locations are 
gusting around 45 miles per hour right now. Expect these winds to strengthen a 
bit further and expand locally into the valleys of Los Angeles and 
Ventura counties. Current wind advisories for the mountains look on 
track to run through noon...and do not anticipate expanding these 
into any other areas. 


Temperatures are running up to 5 degrees cooler than yesterday. Even 
with the offshore flow this morning...expect high temperatures to follow 
this trend...anywhere from 2 to 5 degree f cooler than Thursday. 950mb 
temperatures fall 2 to 4 degree c over the area today...and the 
offshore flow shouldnt be strong enough to overcome this. 


On Saturday morning...expect another weak eddy to form...bringing a 
1000 foot marine layer or so into the la coast...possibly reaching 
into the San Gabriel valley. As a ridge builds into the area through 
the day...expect inland temperatures to rise a few degrees. Along the 
coast...however...gradients become weakly onshore by afternoon...and 
temperatures should vary little from todays. The upper ridge continues to 
shift eastward on Sunday...drying out the lower levels enough to 
preclude any marine layer formation...and bringing a bit more 
warming to the entire area. Sunday should be the warmest of the 
period. 


By Sunday night...the models indicate a cutoff low pinching off of 
an upper trough at about 130w. The GFS is the most progressive with 
this feature...which would bring partly cloudy skies to the area as 
early as Sunday night. Have indicated this in the current zones. If 
nothing else...the marine layer should make a return appearance 
across the la and Ventura County coasts. 


Long term (mon-thu)... 
the long range models differ a bit in handling the cutoff low on 
Monday and Tuesday. The GFS has consistently been the quickest with 
this feature...swinging the low through northern Baja California through the 
day on Monday...then building a ridge into California on Tuesday. The 
European model (ecmwf)...however...never actually cuts off the low and swings it 
through about 6 hours slower. The 06z NAM-WRF looks similar to the 
GFS in terms of forming a cutoff system but is more on track with 
the timing of the European model (ecmwf) (at least for as far as it currently GOES 
out). Do not anticipate any wrap around precipitation with this system on 
Monday or Tuesday...and have simply gone with a partly cloudy 
forecast Monday and Tuesday with a night through morning marine layer. 
Temperatures should cool about 5 degrees or so...and overnight lows 
should be a bit chilly for late March. 


On Wednesday and Thursday...another ridge builds into the 
area...warming temperatures back to above seasonal normals...with 
clear skies and little in the way of marine layer expected. 


&& 


Aviation...19/1300z. 
High confidence with most 12z tafs this morning...except lower 
confidence with ksba and oxr taf this morning as LIFR/IFR conds 
should persist through 15z...then become VFR after 17z. Expect gusty 
NE winds across local mountains through 21z today with MDT uddf and low level wind shear 
for kbur and kvny through early afternoon hours. Otherwise...high 
confidence for VFR conds. 30 percent chance of stratus after 10z 
tonight for la/vtu coastal areas. 


Klax...high confidence in 12z taf. 30 percent chance for MVFR ceilings 
developing through 15z. Otherwise VFR conds expected. 


Kbur...high confidence with 12z taf. 20 percent chance of IFR ceilings 
through 15z developing. MDT low level wind shear possible through 22z this 
afternoon...otherwise expect VFR conds through tonight. 


***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... 
Wind Advisory (see laxnpwlox). 


&& 


$$ 


Public...meier/rat 
aviation...Kaplan 
synopsis...meier 


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