390 
fxus66 kmtr 231715 
afdmtr 


Area forecast discussion 
National Weather Service San Francisco Bay area California 
915 am PST Monday Nov 23 2009 


Discussion...as of 9:15 am PST Monday...clear skies over night lead 
to areas of patchy fog in the valleys this morning. Low temperatures 
dropped into the low to middle 30s in the northbay valleys and remained 
in the upper 30s to low 40s elsewhere. Today will be mostly sunny 
under a ridge of high pressure anchored over the eastern Pacific. 
Under clear skies afternoon temperatures are expected to reach into 
the 60s. 


Model solutions are indicating that the ridge of high pressure will 
migrate slightly east over the County Warning Area tomorrow. At the surface a 
thermal trough will develop along the central coast resulting 
in offshore flow. The combination of offshore flow and the 
eastward migrating ridge will push temperatures up a few degree 
tomorrow to near normal levels from Monterey north to around 5 
degrees above normal south of Monterey. These pleasant dry 
conditions will last through Thanksgiving day. 


Thanksgiving day will be mostly dry across the County Warning Area. However...the 
medium range models have been persistent on moving a trough into 
the Pacific northwest. As the trough moves onshore it will slide a 
cold front across northern portions of the County Warning Area. Ahead of the cold 
front winds will shift out of the south advecting warm air into 
the County Warning Area. With this in mind forecasted temperatures maybe a little 
low for Thanksgiving day. Therefore...will take a closer look at 
the afternoon temperature for Thursday in the afternoon forecast 
package. Another result of the cold front will be a slight chance 
of precipitation Thursday evening with the best chance of 
precipitation in the northbay area. However...the 1200 UTC GFS 40 
does indicate precipitation pushing as far south as Monterey by early Friday 
morning. 


&& 


Aviation...as of 3:37 am PST Monday...mostly VFR conditions 
dominate this morning with the exception of ksns. Light north to 
northeast flow has helped to keep much of the coast cloud free. 


Vicinity of ksfo...VFR conditions today. 


Ksfo bridge approach...VFR conditions today. 


Monterey Bay terminals...LIFR conditions at ksns with visibility less than 
a mile. Expect this to continue through middle morning. Monterey 
remains VFR...but could see some patchy fog late. 


&& 




Mtr watches/warnings/advisories... 
... Craft for rough bar 




$$ 


Public forecast: Larry 
aviation/marine: mm 


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