700 
fxus66 kpqr 080331 
afdpqr 


Area forecast discussion 
National Weather Service Portland or 
830 PM PDT sun Sep 07 2008 


Synopsis...an upper ridge over the eastern Pacific will be the 
persistent large scale feature through much of the coming week. There 
will be some weak upper level disturbances riding over the ridge and 
down into the Rocky Mountain region that will affect the onshore flow 
and marine layer at times. One disturbance to our north will turn the 
flow onshore Monday night and Tuesday as an upper trough carves out 
over the Rocky Mountain region again. The upper ridge will then 
rebuild Wednesday and Thursday for another warming period before the 
next disturbance returns onshore flow to the area at the end of the 
week. 
&& 


Short term...clear skies will continue over the region tonight 
including the coastal waters...but there could be some minor fog 
patches near the coastline toward daybreak Monday. The surface thermal 
trough will remain close to the coast tonight and early Monday...for 
another pleasant warm late Summer day in the northwest. Inland temperatures will be 
close to those today. 


The thermal trough shifts east late Monday and reaches east of the Cascades 
Monday evening as a weak upper disturbance moves in from the northwest... 
turning the low level flow onshore and developing a marine layer on 
the coast that will push into the coastal gaps overnight Monday night. 
The models are showing a fair amount of low clouds inland Tuesday morning 
for the valleys...lower Coast Range and foothills...that will take 
some time to break up in the afternoon. The Cascades and higher Coast 
Range peaks appear to remain above the clouds although temperatures will be 
lower in a cooler air mass. Clouds may persist on the coast and near 
the mountains through much of the day as the westerly onshore flow 
remains strong all day. Will need to watch whether we can get some 
drizzle on the coast early Tuesday. 


Clouds will continue Tuesday night and Wednesday morning...then clear Wednesday 
afternoon as higher pressure begins to build back into the Pacific northwest. Rain shower 


Long term...no changes. Previous discussion follows... 
high pressure builds over the Pacific northwest 
Wednesday night into Thursday for clearing skies and some warming on 
Thursday. This will be short-lived however as an upper level trough 
moving into British Columbia flattens the ridge Thursday night into 
Friday. Onshore flow should return Friday through the weekend...for 
cloudy conditions and a return to more normal temperatures Friday and 
Saturday. Latest model runs indicate a rebuilding of the ridge to 
begin next week...will have to wait for further runs to solidify this 
solution. Brown 
&& 


Aviation...high offshore extending into northern rockies tonight. 
Thermal trough along coast shifts offshore overnight. Thermal trough 
shifts to central Oregon Monday afternoon. Northerly flow this 
evening becomes light offshore later tonight and Monday morning. 
Northwest flow increases Monday afternoon as thermal trough shifts 
east. VFR conditions over all the area tonight. A few fog patches 
are possible along the coast late tonight and early Monday with 
local IFR conditions. Conditions will remain VFR on Monday. 


Kpdx and approaches...VFR conditions in the kpdx area tonight and 
Monday. 
&& 


Marine...strong high pressure offshore tonight and Monday. Thermal 
trough along coast shifts offshore later tonight. Thermal trough 
shifts back ashore Monday morning then moves further inland Monday 
afternoon. Small craft winds will retreat to the outer waters after 
midnight. Small craft winds will gradually push to beaches Monday as 
the thermal trough shifts eastward. Seas will remain below 10 feet 
tonight and Monday. Hazardous seas due to choppy seas from wind 
generated waves will occur over the central coast tonight and Monday 
morning and over all the waters Monday afternoon. 
&& 


Pqr watches/warnings/advisories... 
or/WA...Small Craft Advisory for winds Cape Shoalwater to Florence 
through Monday night. 
Small Craft Advisory for hazardous seas Cascade Head to 
Florence tonight through Monday night. 
Small Craft Advisory for hazardous seas Cape Shoalwater 
to Cascade Head Monday afternoon and Monday night. 
&& 


Preliminary point probability of precipitation (probability of measurable precipitation) 
AST 00111- pdx 0001-- sle 000--- eug 000--- 


$$ 


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.