642 
fxus66 ksgx 212029 
afdsgx 


Area forecast discussion 
National Weather Service San Diego California 
200 PM PDT sun Mar 21 2010 


Synopsis... 
widespread high clouds with areas of coastal low clouds and fog 
tonight. More clouds and cooling Monday and Tuesday as upper level 
low pressure moves through...bringing a slight chance for showers to 
portions of San Diego County. Warmer again Wednesday and Thursday 
under high pressure then a little cooler toward the end of next week 
as the high weakens. 


&& 


Discussion...for extreme southwestern California including Orange... 
San Diego...western Riverside and southwestern San Bernardino 
counties... 


This afternoon...the low clouds and fog associated with a shallow 
marine layer...less than 1000 feet deep...have been pushed offshore 
this afternoon. The fog and stratus is expected to move ashore and 
spread inland overnight as the marine layer deepens. 


The upper level low to the southwest continues to bring extensive 
high clouds over much of socal as the upper level ridge continues to 
weaken. Another upper level low now sits off the coast of British 
Columbia. The locations of these lows results from a split in the 
upper level flow over the eastern Pacific. 


The high pressure ridge will continue to slowly weaken with gradual 
deepening of the marine layer and lower temperatures near the coast 
spreading farther inland Monday and Tuesday as the upper level low 
to the southwest moves into northern Baja California. The low to the north will 
move southeastward in to the Great Basin. The passage of these 
lows should be mostly dry for southwest California with the main 
impacts being to bring more cooling and more clouds. 
However...numerical models are now converging on a solution where 
the upper low moving into Baja California is likely to produce showers over 
northern Baja California as well as the southern portions of San Diego County 
late Monday night and into Tuesday morning. 


Wednesday through Sunday...fair and a little warmer under weak high 
pressure for Wednesday and Thursday. A possible trough of low 
pressure for Friday would bring cooling and a slight chance of light 
precipitation though the current forecast is kept dry for now given 
the poor model to model and run to run continuity with this trough. 
Fair and warmer for Saturday and Sunday with high pressure aloft. 


&& 


Aviation... 
212130z...sct-bkn low clouds based 300-500 feet mean sea level with tops around 
800 feet mean sea level over the coastal waters otherwise mostly clear with 
unrestricted visibilities. After 02z broken-overcast low clouds coastal 
waters reaching inland about 5 miles by 12z Monday...with bases 
300-500 feet mean sea level and tops around 800 feet mean sea level. Widespread 
visibilities below 3sm within about 5 miles of the coastline...and 
areas of visibilities below 1/2sm in dense fog. Small 


&& 


Sgx watches/warnings/advisories... 


California...none. 


Pz...none. 


&& 


$$ 


Public...pg 
aviation/marine...small 


National Weather Service on the web at weather.Gov/sandiego