391 
fxus66 klox 211217 
afdlox 


Southwest California area forecast discussion 
National Weather Service Los Angeles/Oxnard California 
417 am PST Sat Nov 21 2009 


Synopsis...high pressure will build in today as a storm system 
exits the region. An offshore flow pattern will develop for next 
week...creating a warming and drying trend. Windy conditions are 
possible in the vicinity of canyons and passes for midweek next 
week. 


&& 


Short term...latest satellite imagery indicates the trough axis 
residing over southeastern California and the remnants of a cold 
frontal boundary currently exiting Los Angeles County. Main 
residual shower activity is occurring along the northern slopes 
and the Carrizo Plain this morning. Showers should persist 
throughout the this morning along the northern slopes...possibly 
lingering a bit more on the peaks in the afternoon. Some 
localized canyons winds are occurring through the Interstate 5 
corridor and over the southern Santa Barbara County. Gradients 
remain moderately out the north...but are approaching near 
advisory level criteria. These winds will have to be monitored 
throughout the early morning as the latest NAM-WRF and local 
16-km WRF solutions have beefed up the 850 mb winds and thermal 
support through 18z this morning. 


Weak ridging will build in over the area this afternoon and 
tonight...but a weak system moving to the north of the area will 
push a weaker boundary south Sunday. The main threat will be low 
clouds and some sprinkles across the interior valleys and north 
to northeast facing slopes. Probability of precipitation were bumped slightly for this 
period...but with front weakening at it crosses over the San 
Francisco Bay area...best estimate is not to add mentionable probability of precipitation 
and weather just yet. This front will however increase the winds 
through the Interstate 5 corridor and over southern Santa Barbara 
County. There is a chance that advisory level winds may occur. 
Ksba-kbfl and klax-kbfl surface gradients increase to around 6 mb 
out of the northeast and north respectively. This front will also 
kick around the winds to the northeast for late Sunday night and 
Monday morning...precluding a developing Santa Ana flow pattern. 


Long term...with offshore flow firmly taking hold over the 
area next week...a warming trend will become more pronounced for 
midweek. Good model agreement exists between the flow pattern 
gaining strength on Monday night into Tuesday morning...and 
continuing into Thanksgiving day. There is chance that advisory 
level winds could develop with the pattern...and possibly fire 
weather conditions could reach critical levels for midweek. The 
package was warmed for the period as NAM-WRF and GFS solutions 
push the thermal trough well offshore by Tuesday. Temperatures 
were warmed up especially for the central coast on Tuesday...and 
kept warm for the valley area and coastal areas south of Point 
Conception into Thanksgiving day. 


For the remainder of the Holiday weekend...models continue to 
diverge on the developing the storm system for late next week. 
GFS solutions remain less aggressive while the European model (ecmwf) and Gem push 
a trough south over central California. Reasonably good agreement 
exists between all the solutions through Thursday night with a 
trough developing along the West Coast. However...the GFS dampens 
the wave a little too quickly versus the European model (ecmwf) and Gem. With the 
Gem and European model (ecmwf) in better agreement through the weekend...the 
forecast was hedged towards a cooler solution for the remainder 
of the weekend. 


&& 


Aviation...21/1215z. 
A low confidence forecast...with patchy low clouds bouncing about 
behind the weak cold front. Many taf sites will probably have to 
deal with scattered v broken conditions with little rhyme or reason. Most 
locations will only experience MVFR conditions...aside from kprb 
where there may be some IFR ceilings. 


Klax and kbur...scattered v broken conditions this morning with MVFR 
conditions at times...followed by VFR conditions this afternoon. 


&& 


Lox watches/warnings/advisories... 
Small Craft Advisory (see laxmwwlox). 


&& 


$$ 


Public/synopsis...Hall 
aviation...Sweet 


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