Weather

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Area forecast discussion 
National Weather Service Portland or 
300 PM PDT Sat Oct 11 2008 


Synopsis...a ridge of high pressure aloft offshore will slowly move 
inland through early Monday. Westerly flow aloft will set up over the 
region next week with a few weak Pacific fronts moving inland to the 
north of our area...brushing the northern zones with clouds and some 
light rain at times. 
&& 


Short term...visible satellite image this afternoon showing clearing 
skies over the entire forecast area as a positive tilt upper ridge 
builds offshore and approaches the forecast area. Under clearing 
skies observations indicate more seasonal high temperatures are not 
out of reach this afternoon so current forecast looks to be on track. 
Skies will remain mainly clear overnight tonight...and with a good 
amount of moisture still near the surface radiative conditions 
overnight will once again produce areas of fog toward morning. Valley 
temperatures should fall below freezing again for Sunday morning...and a 
frost advisory is currently in effect over much of the area. Tuesday 
should be a repeat of today as the upper level ridge moves over the 
area...with light low level flow and clearing of low level fog 
towards afternoon. Considerable sunshine on Sunday should give 
further warming to near middle Oct normals. 


The upper ridge will begin to flatten and shift inland on Monday which 
should result in weak onshore flow and increasing clouds...especially 
in the north. May begin to see a few showers in the far northern part of 
the forecast area with the onshore flow Monday and Monday night. 


A public information statement is also in effect to cover low water 
conditions around the Portland and Vancouver Harbor areas in the 
Willamette and Columbia rivers as sand bars and other underwater 
objects may be a hazard to boaters this Holiday weekend. Brown 


Long term...models all seem to generally agree on a rather flat 
westerly upper level flow through the end of the week before more 
prounounced troghiness develops into next week. Mostly minor 
impulses brushing by to the north bringing some clouds and rain to 
the northern zones and Cascades through the week and into the 
weekend. 
&& 


Aviation...VFR conditions are expected through the evening. The 
airmass will once again stabilize tonight for areas of IFR/LIFR fog. 


Kpdx and approaches...VFR conditions will continue through the 
evening. LIFR fog will likely form at the terminal after 10z tonight 
as the airmass further stabilizes. 
&& 


Marine...high pressure offshore with thermal trough on the northern 
California coast will remain for a few days. Seas will remain below 
10 feet through at least the beginning of next week. 
&& 


Pqr watches/warnings/advisories... 
or/WA...frost advisory in effect from 5 am to 9 am Sunday for the 
Coast Range of northwest Oregon...the central Coast Range of 
western Oregon...the lower Columbia...greater Portland 
metropolitan area...central Willamette Valley...south 
Willamette Valley...western Columbia River gorge...Willapa 
Hills...I-5 corridor in Cowlitz County...and the Greater 
Vancouver area. 
Public information statement for low water around the 
Portland and Vancouver harbors in the Willamette and 
Columbia rivers. 
&& 
$$ 


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.