788 
fxus66 klox 211226 
afdlox 


Southwest California area forecast discussion 
National Weather Service Los Angeles/Oxnard California 
426 am PST Friday Nov 21 2008 


Short term (today-sunday)...strong northerly gradient remains in 
place over the area as klax-kbfl and ksba-kbfl remain strong 
offshore at this time. With NAM-WRF 950 mb thermal gradients near 
12 degrees and 850 mb thermal gradients near 5 degrees celsius 
currently through the Santa Barbara mountains...Wind Advisory was 
extended until 9 am this morning. However...continuance of the 
advisory was marginal considering a lack of upper-level support. 
Thus...some weakening could occur in the winds and the advisory 
may be cancelled early. 


Temperatures were bumped up for the central coast today with 
offshore gradients likely firmly in place over the area. 
Temperatures are currently running about 10 degrees warmer versus 
this time last night. NAM bufr data indicates offshore flow 
remaining over ksbp and ksmx through a majority of the 
day...while NAM-WRF boundary layer winds indicate offshore flow 
occurring through at least noon today. Otherwise...temperatures 
will likely warm over most areas with offshore flow in place at 
lower to middle levels. 


Some concern exists for possible marine layer development tonight 
over the Los Angeles County coast as southwest flow aloft 
establishes over the area and a lower level southeast flow 
pattern develops. With high-level moisture obscuring the stratus 
deck beneath and dew points remaining in the upper 40s to lower 
50s at klax and klgb...it cannot be ruled out that marine layer 
could not pop up once the high level moisture clears late tonight. 
Latest NCEP 4 km WRF solutions Arkansas hinting at this a well in the 
surface relative humidity pattern. 


A southeast low level will take hold of the area on Saturday night 
and Sunday...bringing stratus north into the Los Angeles County 
coast and possibly into the Ventura County coast by early Sunday 
morning. With the marine influence developing...temperatures 
should cool on Sunday. 


Long term (monday-thursday)...widely varying model solutions 
continue to make problems for the long term period. Latest GFS 
solutions continue to indicate the system impacting portions of 
the area from Monday afternoon through Wednesday afternoon...while 
the European model (ecmwf) solution holds the systems impact until Tuesday morning 
through Thursday morning. The Gem model seems to fall more in line 
with the European model (ecmwf)...but the Gem offers a weaker solution relative to 
the European model (ecmwf). 


Previous shift removed probability of precipitation and weather reflecting the weaker 
solutions...but confidence remains higher that at some point 
during next week precipitation will occur over portions of the 
area...it is just a matter of when and how intense the 
precipitation will be. Both European model (ecmwf) and GFS offer up favorable 
ingredients for precipitation to develop...including warm air 
advection...moisture...and jet dynamics. As a result...probability of precipitation were 
trended to more to climatological levels with largest probability of precipitation numbers 
skewed to the period on Wednesday when the blend of the model 
solutions would indicate the highest probability of precipitation. 
Hopefully...these issues will be resolved later today when the 
NAM-WRF and UKMET have their day in the period. 


A stronger and colder trough appears on tap for late next week 
depending on the which model one prefers. Model timing issues 
continue for late week as well...but GFS and European model (ecmwf) are good 
agreement that a cold system will drop south late in the week. 
Run-to-run consistency continues to pose problems for this system. 
Several different possibilities are shaping up for this system. It 
could range from an inside-slider type system only creating winds 
as the latest European model (ecmwf) suggests...or a significant cold storm system 
bringing wintry weather to the mountains as the current GFS 
solution suggests. For now...temperatures were nudged down a bit 
for late week with a climatological pop trend continuing. 


&& 


Aviation...21/1200z... 


Generally VFR conds S of Point Conception today. High clouds will 
continue to stream across the area most of the day. Some low level wind shear will 
be possible early this morning across the mountains of la/vtu...as well 
as the hills above ksba through 15z. Good confidence for MVFR ceilings 
across the interior valleys of slow/sba counties through 17z. Some 
IFR conds will be possible near kprb this morning as well. Skies 
should remain mostly VFR this evening...except for a return of 
MVFR ceilings across the interior slow County after 05z tonight. 


For klax...good confidence for VFR conds through today...with the 
exception of the possibility of MVFR visibilities until 17z this morning. 
No wind issues. Good confidence for VFR conds through this 
evening. Could be some MVFR visibilities after 10z tonight. 


For kbur...high confidence in VFR conditions today through 
tonight. No wind issues are expected during the period. 




&& 


Lox watches/warnings/advisories... 
red flag warning (see laxrfwlox). 
Wind Advisory (see laxnpwlox). 
Small Craft Advisory (see laxmwwlox). 


&& 


$$ 


Public...Hall 
aviation...Kaplan 


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