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fxus66 klox 101158 aaa 
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Southwest California area forecast discussion 
National Weather Service Los Angeles/Oxnard California 
400 am PST Wednesday Mar 10 2010 


..updated aviation discussion... 


Synopsis... 


A cold air mass will remain in place through Thursday as a weak 
trough moves the region. A strong surface gradient across the area 
will continue windy conditions...particularly in the mountains and 
Antelope Valley. A warming trend will develop over the area on 
Thursday as high pressure builds over the region. A cooling trend is 
expected Saturday with a chance of rain north over the central coast. 


&& 


Short term (today-fri)... 
a weak cold front over Monterey County is actually a little 
stronger than expected and it will produce scattered showers over 
slow and sba counties this morning as well as the north slopes of 
the l.A. And vta County mountains. Heavy rain was briefly reported 
at kmry and ksns so a brief heavy shower is also possible. This is a 
fast moving front however and will not produce much more than a 
tenth of an inch of rainfall. Snow levels remain low and there could 
be snow as low as 3000 feet this morning but again nothing too heavy. 


Winds continue to be vexing as the WRF which was sort of end of the 
worldish last night has toned things down substantially. Current 
assortment of wind warnings and advisories look good. The best winds 
will be in the mountains of la and vta counties especially through the I-5 
corridor. The winds will peak later this morning as the cold air 
behind the cold front sweeps in there will be a secondary peak early 
this evening as the upper flow aligns nicely with the low level 
winds with enough cold air to help transport these winds down. 


The sba mountains and south coasts will likely need wind advisories again 
late this afternoon and evening. 


There will be a quick shift in the winds overnight as the north flow 
turns northeast. This will quickly shut off the north wind favored 
areas and light up the northeast favored locations. The northeast 
push is nowhere near as strong as todays winds and there will likely 
be no need for advisories. 


Maximum temperatures today will be quite cool with 545dm thickness overhead. Again 
maximum temperatures will be 5 to 10 degrees below normal. 


Speaking of cold Wednesday night will be quite chilly in some 
locations. With a very dry and cool airmass in place overnight lows 
in non breezy locations will fall into the 30s with some inland valley 
and desert locations seeing freezing temperatures. It will be very 
difficult to figure out exactly where the coldest temperatures will be 
because any amount of winds will keep the temperatures 10 degrees warmer 
than calm locations. 


Thursday will see a dramatic change in the weather. A 572dm ridge 
quickly builds in and this combined with the offshore flow will 
allow for a dramatic leap in temperatures of 5 to 10 degrees across the 
board with the greatest gains across the la and vta valleys. 


Friday is no longer looking quite as warm as forecast ydy. The front 
that was forecast for Saturday is now on track for a Friday night 
arrival. This mean that the ridge will break down faster on Friday 
and the offshore flow will be weaker. There will also be more high 
level clouds overhead. It will still be a nice day but just not as 
nice as we hoped and probably a degree or two cooler than Thursday. 


Long term (sat-tue)... 
like all fronts lately the Friday night Saturday morning one looks 
to fall apart as it rounds Point Conception. Right now will go with 
a chance of rain north of Point Conception and some North Slope 
rain for the la. Vta mountains did not bump probability of precipitation up higher than chance to 
account for the timing issues whether the rain will arrive Friday 
night or Sat morning. The front is fast enough moving that rain will 
likely not affect both periods. Elsewhere it will make for cooler 
Saturday with heights falling to 565 dm and plenty of clouds. Temperatures 
will fall about 5 degrees across the board. 


Both GFS and ec forecast another longer lasting ridge to build into 
the area Sunday and last into Tuesday. Look for mostly clear skies 
and temperatures warming to above normal by Monday and maybe a few more 
degrees above normal Tuesday. 


&& 


Aviation...10/1200z. 


A gusty northwest to north flow pattern will persist across the area 
through the taf period. The northerly flow may produce some 
scattered showers north of Point Conception this morning but expect 
any ceilings to remain at VFR levels. With the northerly flow...some 
gusty winds along with turbulence and low level wind shear can be expected 
especially through/below passes and canyons. 


Klax...moderate to high confidence in 12z taf. With the north 
flow...there could be some low level wind shear and light turbulence this morning 
around the airfield. 


Kbur...moderate to high confidence in 12z taf. Northerly flow will 
produce some gusty winds at the airfield along with low level wind shear and some 
turbulence. 


***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... 
High Wind Warning (see laxnpwlox). 
Wind Advisory (see laxnpwlox). 
Gale Warning (see laxmwwlox). 
Small Craft Advisory (see laxmwwlox). 
High rip current risk (see laxsrflox). 


&& 


$$ 


Public...rorke 
aviation...Thompson 
synopsis...asr 


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