282 
fxus66 ksgx 210433 
afdsgx 


Area forecast discussion 
National Weather Service San Diego California 
930 PM PST Thursday Nov 20 2008 


Synopsis...a shallow marine layer will cause areas of coastal low 
clouds and fog during the nights and mornings. There will also be 
variable high cloudiness in westerly flow aloft. Upper level low 
pressure approaching from the west will bring more clouds and 
cooling next week with a chance of showers by middle week. 


&& 


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


Short term (tonight-sun)...there were low clouds and fog near the 
coast and variable high cloudiness this evening. The 00z nkx 
sounding had a weak inversion based below 1000 feet and showed the 
high level moisture in westerly winds aloft. Weak offshore gradients from 
the north and onshore to the east. 


Flat westerly flow aloft will become weakly cyclonic late Sat. A upper 
level ridge will develop ahead of a trough digging into the east Pacific 
sun but local heights will not change much. A surface high will move 
past to the north Friday and will briefly cause local weak offshore flow 
Friday morning. There will be local gusty winds through and below 
mountain canyons and passes Friday morning. The strongest winds will be 
below the Cajon Pass and in the Santa Ana Mountains were they could 
gust to 35 miles per hour. Gradients will become very weak Sat and then 
stronger onshore sun. The shallow marine layer tonight will bring 
areas of coastal low clouds and fog. The fog will be locally dense. 
The offshore flow will reduce the marine layer clouds by Friday 
morning...especially in Orange County. The marine layer will return 
and deepen a little Friday night with more deepening Sat night. 
Variable high cloudiness will continue in west to SW flow aloft. Warmer 
west of the mountains Friday due to the offshore flow then a little cooler 
Sat but maximum temperatures will still be about 5 to 10 degrees above seasonal 
inland Sat. More cooling sun as onshore flow increases. The brief 
dry offshore flow will increase the fire weather hazard Friday but 
critical fire weather conditions are not expected. 


&& 


Long term (mon-thu)...the generally preferred European model (ecmwf) was followed 
for the extended period. The cooling trend and deepening marine 
layer will continue Monday. The low off the coast will slowly shift east 
and could tap into tropical moisture. The details remain uncertain 
but it looks like there should be more clouds and cooling with a 
chance of showers late Tuesday and Wednesday. The snow level will start very 
high due to the mild SW flow ahead of the trough. If this system 
develops as expected then it could produce substantial 
rainfall...especially on the SW facing mountain slopes. Colder with 
a lowering snow level Thursday as the upper low moves through. Showers 
should taper off Thursday afternoon. 


&& 


Aviation... 
210430...stratus/fog will mostly be restricted to within 5 miles of 
the coast overnight. Some retreat of the stratus/fog will occur after 
10z. Ceilings will mostly be under 500 feet mean sea level...and areas of dense fog 
will occur. Kcrq has already been impacted by visible below 1/2 mile. 
Ksan could potentially be impacted after 10z...though most likely on a 
tempo basis. Ksna will be less likely to be impacted as weak 
offshore flow will keep most of the fog out after 08z. Stratus/fog 
clearing should occur in most if not all areas by 16z Friday and is not 
likely to return until after 04z Sat (fri night). 


Above the marine layer...variable high clouds above fl200 and 
unrestricted visibilities will continue. 


&& 


Sgx watches/warnings/advisories...none. 


&& 


$$ 


Public...atkin 
aviation...Maxwell