Weather

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Area forecast discussion 
National Weather Service Portland or 
900 PM PDT Friday Oct 10 2008 


Synopsis...a ridge of high pressure aloft offshore will slowly move 
inland by Sunday. 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. 
&& 


Short term...drying north to northeast flow aloft over the area as a 
positive tilt ridge of high pressure aloft builds offshore. Clouds 
will continue to thin and decrease. The positive high pressure area 
aloft is already nosing into western Canada which is turning the flow 
northeast and as clouds decrease over such a cool air mass expect the 
coolest night of the fall by Sat morning. The morning minimum 
temperatures will be especially cool in the High Mountain valleys 
where a couple inches of new snow fell. Terrestrial radiation will be 
high there tonight with some minimum temperatures in the 20s. Many areas of 
the Willamette Valley will see temperatures fall below freezing 
tonight...will continue the frost advisory. Fog will develop later 
tonight into Saturday morning in The Lowlands. It will be a cold 
start for Sun morning as well as the air mass warms a bit but dries 
out more to help night time radiation. 


A public information statement was also issued 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. Likens 


Long term...no changes. Previous discussion follows...models all 
seem to generally agree on a rather flat upper level flow through the 
extended. However there is significant disagreements exist in the 
timing of disturbances moving through...making for a low confidence 
forecast. Subsequently chose not to change much for the afternoon 
package...keeping freezing levels rather high...temperatures mild and any 
chances of rain confined to the Cascades and northern reaches of the 
forecast area. Dalton 


&& 


Aviation...VFR conditions will prevail overnight...with possible 
IFR fog forming late tonight in sheltered interior valleys. Any fog 
that does form will burn off by midday. 


Kpdx and approaches...VFR conditions will prevail tonight. There is 
a 30 percent chance of IFR fog between 10z and 17z Saturday morning. 
&& 


Marine...winds have fallen below small craft levels across the 
waters this afternoon and will remain that way 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 6 am to 9 am Saturday 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.