063 
fxus66 kpqr 112127 
afdpqr 


Area forecast discussion 
National Weather Service Portland or 
230 PM PDT sun may 11 2008 


Synopsis...a cool upper level trough will move east of the area 
tonight with high pressure building into southern Oregon. High 
pressure will build along the coast Monday. A warm front will brush 
the north Oregon coast and South Washington coast Monday night...then 
lie across the northern part of the forecast area Tuesday into early 
Wednesday morning for a chance of precipitation. A strong upper ridge will 
build into the area late in the week bringing very warm temperatures 
to the region. 
&& 


Short term...radar and surface observations show light scattered 
showers over the Coast Range and Cascades this afternoon as the upper 
level trough moves across the region. A few valley locations have 
also reported a trace of precipitation this afternoon. Isolated showers 
will continue through early evening until the trough axis passes to 
the east. Later tonight and Monday...a ridge of high pressure will 
move into the area which will weaken the onshore flow and bring a 
pleasant day to start the work week. The past couple of days the 
models have struggled with the evolution of the building upper level 
ridge and warm front for the Tuesday-Wednesday time frame. Latest couple of 
model runs seem to be honing in on a solution to bring the warm front 
along the or/Washington coast Monday night...then become east-west oriented 
across the northern part of the forecast area Tuesday through early Wednesday 
morning. Satellite imagery across the Pacific show some tropical 
moisture has entrained into the westerlies...which may provide some 
additional precipitable water with the warm front as moves into the 
area on Tuesday. Per coordination with neighboring offices have added 
some chance probability of precipitation to the northern part of the forecast area for Tuesday 
and early Wednesday. Tw 


Long term...warm...dry...and sunny weather in the forecast for the 
long term. The forecast area will experience quite warm and possibly 
near record temperatures to end the week. A strong upper level ridge 
and the formation of a strong thermal trough along the coastline set 
up Wednesday night and Thursday and persist through Friday night and into Sat. 
Models in somewhat agreement breaking down this ridge and moving the 
thermal trough east of the Cascades during the day Sat...for a 
return of onshore flow and near normal temperatures. This weather 
pattern will produce a marine push Saturday and into Sunday for 
cloudy weather and the possibility of light rain. Brown 
&& 




Aviation...VFR conditions through tonight. Weakening onshore flow 
will bring MVFR conditions at times to the coast after 04z...and 
increasing chances of MVFR inland after 11z or so. Scattered 
showers mainly over the mountains but a few will probably move 
across the north Willamette Valley into SW Washington through early 
evening...then diminish. 


Kpdx and approaches...expect VFR to prevail through tonight. Though 
chances for some MVFR ceilings a few hours Monday morning...around 13-16z. 


&& 


Marine...seas and winds below advisory criteria for the next 
several days...but a warm front brushing the northern zones on Tuesday 
could bring southerly winds to near Small Craft Advisory. Later in 
the week...high pressure over the NE Pacific with thermally induced 
through strengthening along the coast will probably bring small 
craft northerlies Thursday and Friday. On the Columbia River bar...seas are 
high enough for rough bar conditions during the next two ebbs. 


&& 


Pqr watches/warnings/advisories... 
WA/OR...Small Craft Advisory for rough Columbia River bar this 
evening and Monday morning. 
&& 


Preliminary point probability of precipitation (probability of measurable precipitation) 
AST 213352 pdx 211221 sle 211111 eug 2-1111 


$$ 


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.