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afdpqr 


Area forecast discussion 
National Weather Service Portland or 
215 PM PDT Sat Mar 20 2010 


Synopsis...a weak cold front will move into southwest Washington and 
northwest Oregon this evening with a threat of rain. Cooler air will 
follow with the bigger threat of showers Sunday. Another Pacific 
system is expected after middle week. 


&& 


Short term...from satellite imagery...it appears a weak front is 
moving across the western border of the coastal waters early this 
afternoon. Speed predicts landfall 22z-23z. Still the main 
precipitation threat appears to be with and ahead of the upper trough 
Sunday. NAM and GFS are handling this good. Snow levels dropping to 
near pass levels Sunday...but snow amount expected to be around but 
mostly below advisory levels with this system. 


Flow remains cyclonic with the slow exit of the upper trough Monday 
with a slow tapering off of showers. Then the upper ridge building 
strongly over the County Warning Area by Tuesday. And it must be Spring with a 
surface high building inland Tuesday and a thermal trough pushing 
northward along the coast. Sunset 


Long term...GFS and European model (ecmwf) similar through middle week...then diverge a 
little on amplitude and phase by the end of the week. Will follow the 
GFS through the extended period with below climatology probability of precipitation late in 
the period. Sunset 


&& 


Aviation...offshore flow continues to weaken through later this 
afternoon...light southerly flow has developed along the coast. 
Ceilings have quickly risen to MVFR on the S coast...with low stratus 
and fog expected to move up the Oregon coast this evening. 
Inland...just middle and high clouds. Biggest threat for VFR/MVFR 
clouds inland will be after 05z. 


Kpdx and approaches...VFR conditions through 05z. After wards... 
expect some MVFR ceilings overnight. Winds turn more southerly before 22z 
as marine layer begins increasing over S Willamette Valley. Ramirez 


&& 


Marine...low pressure over the NE Pacific continues to move NE into British 
Columbia. Weak front will push onshore after 00z. Expect gusty S 
to SW winds over the waters. Strongest winds will be over the 
outer waters. Seas slowly build...reaching 10 feet on sun. Ramirez 


&& 


Pqr watches/warnings/advisories... 
or...none. 
Washington...none. 
Pz...Small Craft Advisory for winds until 11 am PDT Sunday for 
coastal waters from Cape Shoalwater Washington to Florence or out to 
60 nm. 


Small Craft Advisory for hazardous seas from 5 am to 11 PM PDT 
Sunday for waters from Cape Shoalwater Washington to Florence or from 
10 to 60 nm. 


&& 


$$ 


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.