123 
fxus66 ksgx 212044 
afdsgx 


Area forecast discussion 
National Weather Service San Diego California 
200 PM PDT Thursday Aug 21 2008 


Synopsis...the marine layer and onshore flow will continue coastal 
low clouds and patchy fog during the nights and mornings...extending 
locally inland. Otherwise...fair weather will continue under high 
pressure and dry flow aloft. Slightly below seasonal temperatures 
will increase to near seasonal averages this weekend and early next 
week. 


&& 


Discussion...for southwest California including San Diego... 
Orange...southwest San Bernardino and West Riverside counties. 


Little change is expected through Friday as dry west flow aloft will 
continue to keep monsoon moisture hundreds of miles to our east and 
south. The moderately strong onshore pressure gradients of about 5 
mb to the deserts will keep the sea breeze going resulting in temperatures 
a little below average...along with the persistent marine layer about 
1500 feet deep. 


As the low pressure trough over the central U.S. Moves to the 
northeast...high pressure over the east Pacific will expand into New 
Mexico through sun. This will likely bring some warming over the 
weekend with temperatures west of the mountains increasing to near seasonal 
averages. The models are in general agreement with the high building 
over New Mexico by Sat and developing some southeast flow which will bring 
a return of some monsoonal moisture into Southern 
California...beginning on sun. By Monday...the 00z ecm has the high 
further north than the 06z GFS...resulting in a more moist ecm 
solution and a drier GFS solution for socal early next week. Either 
way appears marginal for the development of deep convection. The 
models diverge somewhat starting around Tuesday with the GFS being 
faster than the ecm with the movement of shortwave troughs into the 
Pacific northwest and the northern rockies. So from about the middle to the end 
of next week...the models are out of phase with each other in the 
timing of troughs and ridges over the Pacific northwest. Am leaning 
toward the GFS solution with the faster movement of the troughs 
given the current strength of the pfj over the northern Pacific. 


Expect some cooling west of the mountains for the latter part of next 
week as the marine layer strengthens again in response to multiple 
troughs passing to the north. 


&& 


Aviation... 
212035z...strong coastal eddy circulation and south-southeast wind 
10-15kt below fl100 continuing for at least next 24 hours. This has 
kept stratus from completely clearing along coast and over water 
this afternoon. Expect stratus to increase by 0300 UTC to 
broken-overcast with bases near fl010 and tops fl020. By 0600 UTC 
stratus layer expected to be extending up to 30 sm over San Diego 
County...and likely spill into inland Empire through Interstate 15/ 
Rainbow Gap...spreading northward through 1600 UTC before 
dissipating. Lower foothills and terrain above fl010 will be 
obscured in clouds/fog from 0600-1600 UTC. This pattern is also 
favorable for low level moisture moving up from Gulf of California 
across Salton Sea and into Coachella Valley...resulting in a few 
hours of middle morning haze/stratus over lower end of Coachella Valley. 


&& 


Sgx watches/warnings/advisories...none. 


&& 


$$ 


Public...pg 
aviation...Balfour