799 
fxus66 ksgx 231030 
afdsgx 


Area forecast discussion 
National Weather Service San Diego California 
230 am PST Monday Nov 23 2009 


Synopsis...high pressure aloft and weak offshore flow will bring 
fair weather with a warming trend through Thanksgiving day. Cooler 
toward next weekend as a low pressure trough approaches from the 
northwest. 


&& 


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


Upper level high pressure and offshore flow will dominate our 
weather through Thanksgiving...bringing much warmer weather and 
local gusty winds below the passes and canyons. Modest increases in 
500 mb heights and 850 mb temperatures will result in a few degrees of 
warming each day...with maximum temperatures topping out at about 10 degrees 
above seasonal averages by Thanksgiving day. Skies will be mostly 
clear as dry offshore flow scours out the marine layer. 


The upcoming offshore flow will be another gradient driven event. 
Upper level support will be lacking...and thermal/pressure gradients 
are expected to be weak to moderate. Wind gusts below the passes and 
canyons will generally remain below 30 miles per hour...however just as in the 
previous gradient driven event...isolated/occasional gusts from 
40-50 miles per hour are possible in the windiest locations. 


Very dry air is expected with the offshore flow this week. Inland 
humidities will fall below 10 percent each day beginning Tuesday and 
continuing through Thursday. The combination of locally breezy 
conditions and very low humidities will elevate the fire weather 
hazard. 


Long range...the GFS and European model (ecmwf) forecasts for later this week show the 
ridge breaking down Friday ahead of a potent shortwave that will 
bring substantial cooling through Saturday. Behind this trough a 
colder...potentially windy offshore pattern is setting up for next 
Sunday and Monday. 


&& 


Aviation... 
231000 UTC...scattered cirrostratus at or above fl250 currently over 
mountains. Marine layer depth currently between fl010-fl015 with 
visibility at or below 1-3sm in hz/br. Could see some ground fog with 
visibility below 1/2sm in fog between 23/12-23/16 UTC in and around 
reservoirs/river valleys and at or below fl003 near the coast. Expect 
northeast winds 5-15 knots after this will scour out marine air and 
prevail for next 60 hours. 


&& 


Sgx watches/warnings/advisories...none. 


&& 


$$ 


Public...scv 
aviation...Balfour