776 
fxus66 kmtr 220050 
afdmtr 


Area forecast discussion 
National Weather Service San Francisco Bay area California 
224 PM PST Sat Nov 21 2009 


Discussion...as of 2:24 PM PST Saturday...clear skies are being 
reported across the area this afternoon. So far afternoon 
temperatures have made it into the middle to lower 50s which is within 
2 to 3 degrees of yesterday afternoons high temperatures. The 
latest visible satellite image does show clear skies across the 
County Warning Area. However...it also is showing a large area of clouds moving 
towards northern California. This large area of clouds is 
associated with a low pressure system currently in the Gulf of 
Alaska. A cold front resulting from the previously mentioned trough 
of low pressure will slide across the northbay late tonight and 
will bring with it a slight chance of rain and some added cloud 
cover. The added cloud cover will keep the North Bay valleys a few 
degrees warmer than last night. 


Temperatures are expected to warm up a bit this week with the 
ridge of high pressure pushing 500 mb heights to 578 dm Monday 
afternoon. This will result in temperatures warming to middle 60s 
Monday and possibly the low 70s by Tuesday. The warmest temperatures 
will most likely be in the southern Salinas valley with King City 
reaching 72 degrees by middle week. 


Thanksgiving day looks to be mostly dry and pleasant. However...the 
1200 UTC European model (ecmwf) and GFS models do begin to diverge on their 
solutions by Thursday. The European model (ecmwf) insists on dropping a trough of 
low pressure across northern California resulting in a slight chance 
of precipitation for the North Bay area. Meanwhile the operational 
GFS is slower with this feature and appears to lift the trough 
northward into British Columbia sparing the area of precipitation Thanksgiving 
day and into the Holiday weekend. 


&& 


Aviation...as of 4:30 PM PST Saturday...the tail end of a 
frontal system will bring some lower clouds into the sfo Bay 
area late tonight well after the Airport evening rush hour. 
Bases of the ceilings are expected to be 2500-3000 feet but 
confidence is low. 


Vicinity of ksfo...VFR conditions through the Airport evening 
rush hour. Some ceilings at 2500-3000 feet will move in after 
midnight. 


Ksfo bridge approach...same as ksfo. 


Monterey Bay terminals...VFR conditions through Sunday. 


&& 




Mtr watches/warnings/advisories... 
... Pinos to pt Piedras Blancas to 10 nm 
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10 to 60 nm 




$$ 


Public forecast: Larry 
aviation/marine: ssa/west pi 


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