821 
fxus66 kmtr 211730 
afdmtr 


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


Discussion...as of 8:45 am PST Saturday...the first visible 
satellite image of the day is showing mostly clear skies across the 
area this morning. Over night lows were pretty chilly last night 
behind the departing cold front. The chilliest area was of course 
the North Bay valleys with lows in the low to middle 30s. Sonoma 
County Airport made it to 32 degrees and was reporting freezing fog 
this morning. Meanwhile Napa Airport made it down to 36 degrees 
and also reported a brief period of freezing fog. 


Tonight will not be quite as chilly in the North Bay valleys with 
some middle and upper level clouds expected to move in this evening. 
These clouds will form in response to a cold front brushing by the 
area overnight. This front will also bring a slight chance of 
precipitation to Napa and Sonoma counties. The forecast continues 
to dry out tomorrow as a ridge of high pressure builds over the 
eastern Pacific. 


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 
0000 UTC European model (ecmwf) and 1200 UTC GFS models do begin to diverge on their 
solutions by Thursday. The European model (ecmwf) insists on drooping 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 9:30 am PST Saturday...clear skies are expected 
today with only high clouds moving across later today. The 
southern edge of a weak front will bring an increase in clouds to 
the North Bay along with a chance of showers overnight. 


Vicinity of ksfo...VFR conditions through today. West winds at or below 10 
knots expected this afternoon. 


Ksfo bridge approach...VFR. 


Monterey Bay terminals...VFR conditions today and tonight. 
Light west winds expected. 


&& 




Mtr watches/warnings/advisories... 
... For hazard seas pt Arena to Pigeon pt 10-60 nm until 2 PM 
... Pigeon pt to pt Piedras Blancas 10-60 nm 
... Pt pinos to pt Piedras Blancas 0-10 nm 
... Starting 1 PM Pigeon pt to pt pinos 0-10 nm 
... For rough bar conditions until 2 PM 


$$ 


Public forecast: Larry 
aviation/marine: ssa 


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