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afdlox 


Southwest California area forecast discussion 
National Weather Service Los Angeles/Oxnard California 
435 PM PDT Wednesday Jul 23 2008 


Updated aviation section 


Short term (today-saturday)... 
temperatures running about on par from yesterday...as onshore grads and 
thicks are relatively unchanged. Stratus has cleared quite a bit off 
the la/vtu Colorado coast...but is hanging in pretty close to the central 
coast and sba South Coast. Marine layer will be tricky tonight. The 
depth should shrink every so slightly as onshore grads weaken a bit 
and heights increase. Based on the fact that the stratus spread 
completely into the valleys early this morning...mentioned some low 
clouds and fog once again in all coast and valley zones to play it 
safe...though would not be surprised to see clouds only in the 
coasts and the San Gabriel and Santa Ynez valleys by daybreak Thursday. 


With the smaller marine layer and weakening onshore grads...stratus 
should burnoff rather quickly Thursday morning. The high pressure 
centered over New Mexico will get pinched off into two as Hurricane 
Dolly moves to the northwest. Add the weakening onshore grads to the 
equation...and 950mb temperatures and thicks should boost nicely... 
resulting in Thursday and Friday being considerably warmer than today and 
yesterday. NAM showing just under 40c 950mb temperatures in the Antelope 
Valley... which would suggest temperatures well above 100 for the far 
interior sections of the area. There should still be a seabreeze in 
the afternoon which would limit the warming some over the coast and 
coastal valleys. Even still...temperatures should be above normal 
everywhere to close out the work week. 


With high pressure nudging westward and northwest Mexico moistening up 
ahead of Dolly...there is still a possibility of some monsoonal 
moisture moving up into the area. Models have been trending later 
and somewhat drier with this surge...and decided to remove probability of precipitation from 
the la/vtu mountain and deserts for Friday as a result...but kept them 
riding for the weekend. The situation looks similar to last 
week...with a plume of moisture getting advected into south eastern California 
with the edge of the plume just to the east of la County. Like last 
week as well...the southeast flow is short-lived as the foot of a 
rather large trough pushes into northern California Sat night...and shifts the 
flow southwesterly later on sun. Will keep an eye on this 
situation...but at this point it does not look too favorable of our 
area...just like last week. 


Temperatures-wise Sat is very tricky...as the NAM increases onshore grads 
on Sat while the GFS waits until sun. Based on the 12z water vapor 
pattern...the GFS initialized much better than the NAM and am going 
to lean heavier on the GFS as a result. If the NAM proves correct 
however...temperatures would decrease much more than the current forecast 
suggests. 


Long term (sunday-wednesday)... 
as onshore flow increases on sun and high pressure aloft 
weakens...temperatures should decrease on sun and stay about the same on 
Monday. Once the previously mentioned trough moves out of California...high 
pressure will begin to build back into California on Tuesday...and temperatures should 
begin to warm up a bit more over the interior portions. Decent 
onshore flow will moderate that warming along the coast and coastal 
valleys however. There is a shot of middle-level moisture lingering 
around on sun and left the slight chances over the la/vtu Colorado mountains 
and deserts going...but the model trends are scaling back the 
possibility. As the high pushes back westward Tuesday and Wednesday...there is 
another window for some middle-level southeast flow returning...but did 
not bite on this quite yet other than keeping 10 probability of precipitation going through 
the extended. 


&& 


Aviation...23/2330z. 
Marine layer has decreased to about 1000 feet...which has been the 
norm for the past several days during the late afternoons. Low 
clouds holding their own along the central coast and around Point 
Conception to Santa Rosa Island. Expect stratus to redevelop tonight 
for all coastal areas due to a weak eddy circulation across the 
bight. Onshore gradients are just as strong as 24-hours ago and a 
similar marine layer will result in clouds pushing into the valleys 
again late tonight. 


Klax...good confidence in clear skies until late evening when MVFR 
ceilings/visibilities will redevelop...mainly after 05z. 


Kbur...good confidence in clear skies until late tonight when IFR 
ceilings/visibilities return to the valleys...mainly after 09z. 


&& 


Lox watches/warnings/advisories... 
none. 


&& 


$$ 


Public...kittell 
aviation...boldt 


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