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Area forecast discussion 
National Weather Service Portland or 
815 am PDT Thursday Mar 18 2010 


Synopsis...a sharp upper level ridge will continue to build just off 
the coast today as surface high pressure shifts inland turning the low 
level flow offshore. Low level flow will turn back onshore on 
Sat...ahead of an upper level trough moving in for sun and Monday. 
&& 


Short term...other than some local patchy fog along the coast this 
morning...skies are clear across the forecast area. The patchy fog 
will burn off quickly this morning...giving way to sunny skies for 
the entire County Warning Area today. Models are consistent in building the upper 
ridge just offshore today and Friday...before shifting it inland Friday 
night. Northerly low level flow today shifts to easterly by Friday to 
continue drying low level air mass. The offshore flow and building 
heights will bring progressively warmer temperatures today and Friday...well 
above normals for this time of year. 


A more southerly onshore flow to return by Sat as a low ejecting out 
of the longwaves trough out over the Pacific...lifts to the north beyond 
130w. This should result initially in a marine surge Sat...especially along 
the coast. Any real threat for precipitation is likely to hold off until Sat 
night when marine air mass deepens and a shortwave pushes in. 


Long term...no changes. Previous discussion follows...a blocking 
ridge of high pressure offshore keeping the forecast area under very 
mild conditions will begin to move east Sunday as a stronger system 
approaches the coast late Sunday into Monday. This low will 
effectively break down the ridge and allow precipitation to return to the 
area during the first half of next week. 
&& 


Aviation...VFR conditions expected today and tonight. 


Kpdx and approaches...VFR conditions today and tonight. 


&& 


Marine...seas around 10 feet should slowly subside to 8 feet by this 
afternoon. High pressure continues over the northeast Pacific. This 
will give northerly flow over the waters through the week...with 
small craft wind conditions likely through this evening. 


&& 


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


Small Craft Advisory for hazardous seas until 10 am PDT this 
morning for coastal waters from Cape Shoalwater Washington to Florence 
or out 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.