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Area forecast discussion 
National Weather Service Portland or 
232 am PST Monday Nov 23 2009 


Synopsis...a weak warm front off the coast will shift northeast 
today...then a weak cold front will sag southeast into northwest Oregon tonight. 
The front will stall late tonight...then lift NE as a warm front on 
Tuesday. The next frontal system is not expected to move in until late 
Thursday. 


&& 


Short term...radar shows some light precipitation has developed 
over the S Washington foothills early this morning...likely as the result of 
low level warm air advection and orographics. The main threat for 
rain though today should be over the northwest part of the forecast area 
though...where isentropic lift is best ahead of the warm front 
offshore. 


With a shortwave crossing over the top of the ridge through southern 
British Columbia late today and tonight...models indicate a cold front sagging 
down into the region late today and tonight. Will need to include 
probability of precipitation most areas by tonight and early Tuesday with baroclinic zone over 
the area...but with weak dynamics probability of precipitation will be limited to chance to 
likely category. Front lifts back to the north late Tuesday and Tuesday night 
with the upper ridge rebounding...resulting in diminishing probability of precipitation by 
Tuesday night...and a dry day Wednesday. 


Long term...no changes. Previous discussion follows... 
models in some agreement on bringing a frontal system and its 
associated upper level trough through the region Thursday/Thursday night for a 
return to wet weather. After this system moves through...the weak 
high pressure ridge reasserts itself over the forecast area...keeping 
most energy north of forecast area. 


&& 


Aviation...much more tranquil this am. VFR conditiosn across the 
region...and this will change little today. With breaks in the 
ceilings...and light winds...could see patchy fog south of Salem through 
17z. A warm front approaching from the SW will spread areas of MVFR 
with occasional rain along the coast after 20z. Remaining generally 
dry with VFR inland through 02z. 


Kpdx and approaches...no adverse weather impacts expected. VFR 
conditions to remain through 06z tonight. 
&& 


Marine...seas still in the 11 to 14 feet range. But these willl 
continue to subside a bit today...but will remain above 10 feet 
through Tuesday. Breezy conditions expected today and tonight as warm 
front lifts across the coastal waters. Dont see enough support for 
gale force winds...so will cancel gale and just keep at Small Craft 
Advisory today into early evening. 
&& 


Pqr watches/warnings/advisories... 
WA/OR...Small Craft Advisory for hazardous seas Cape Shoalwater to 
Florence through Tuesday. 
Small Craft Advisory for winds Cape Shoalwater to Cascade 
Head today. 
Small Craft Advisory for winds from Cascade Head to Florence 
this afternoon. 
&& 


$$ 


More weather information online at... 
http://weather.Gov/Portland 




This discussion is for northwest Oregon and southwest Washington from 
the Cascade crest to 60 nautical miles offshore. The area is commonly 
referred to as the forecast area.