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fxus66 klox 240335 
afdlox 


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


Update...marine layer 1000 feet deep and similar to last two 
nights. Onshore pressure gradient reached 6.4mb between 
lax-dag...which is the strongest in several days. This all bodes 
well for another night of low clouds and fog for coastal zones and 
parts of valley zones. Stratus and fog has already pushed inland 
from sba to oxr which is a different Twist from last night when it 
moved into lax first. Also of note...the northern extent of the 
stratus is across Morro Bay with clear skies to the north. 


Temperatures today were right about normal for this time of the year 
and a few degrees lower than expected from previous forecasts. 
Previous to tonights model runs...the WRF had been pumping The 
Heights significantly during the week but now it has backed off. The 
00z WRF shows a slightly weaker high pressure area and 950mb 
temperatures of about 38c for Friday and Saturday afternoons. This 
will put temperatures about 5 degrees above normal for the desert 
and mountains...but really not significant for heat-related problem. 
Valleys and coasts will remain about normal due to onshore winds 
each day. 


There is very little indication at this time that the monsoon will 
make it into our region over the weekend. 850mb dewpoint temperatures that 
are critical for monsoon moisture stay too low and may be suppressed 
by the high pressure area sitting over southern calif during the 
period. Thunderstorms were removed from the Friday forecast and may 
need to be trimmed for the remainder of the weekend after further 
review of new model data. 


..from previous discussion... 


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...boldt/kittell 
aviation...boldt 


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