628 
fxus66 kpqr 061554 
afdpqr 


Area forecast discussion 
National Weather Service Portland or 
853 am PDT Sat Sep 06 2008 


Synopsis...an upper ridge over the eastern Pacific will be the 
persistent large scale feature through much of the coming week. There 
are still some weak upper short waves riding over the ridge and down 
into the Rocky Mountain region affecting the onshore flow and marine 
layer. One short wave will cut back and develop off California 
tonight and Sunday that will cause the thermal trough to back to near 
the coast Sunday into Monday for warming and less marine influence. A 
series of short waves to our north will turn the flow more onshore 
beginning Monday night and continuing through middle week as an upper 
trough carves out east of the Cascades. The upper ridge will then 
rebuild late next week. 
&& 


Short term...marine clouds are the big change this morning as clouds 
have pushed south along the east side of the Willamette Valley all 
the way to Eugene. Even though 850 mb temperatures go up a touch today...the 
marine layer will likely cap temperatures at values from Friday...possibly a 
bit lower in the north. 


Models indicate that the onshore flow should be less Sunday morning 
and temperatures thus higher as a piece of energy riding over the eastern 
Pacific upper ridge cuts back to off the California coast. This draws 
the surface thermal trough back toward the coast on Sunday and 
Monday...with even less marine influence Monday. Temperatures both days 
inland should mostly be in the 80s. A short wave will turn the flow 
more onshore late Monday and Tuesday and begin a cooling trend with 
more morning low clouds Tuesday. Tolleson 


Long term...no changes. Previous discussion follows... 
dry and above normal temperatures continue through the extended 
forecast. Only very minor changes made to previous forecast. Guidance 
continues to indicate a strong ridge will be over the Pacific through 
most of next week. Long term models start to flatten the ridge 
somewhat by midweek as the surface thermally induced trough moves 
inland with maximum temperatures cooling to the lower 80s. However...current 
trends build the ridge again by Thursday for continued warm and clear 
days. Brown 
&& 


Aviation...IFR/LIFR marine stratus along the coast...with MVFR/IFR 
stratus filling much of the Willamette Valley this morning. Expect 
stratus to go scattered around 19z to 20z for all inland taf sites. 
At the coast...not much improvement expected today. Clouds may become 
scattered to broken in nature between 21z to 00z...however it will be short 
lived as all guidance has coast returning to IFR status by 00z to 
03z. Clouds should clear from the coast quickly on Sunday morning as 
dry offshore flow sets up earnest. Additionally no inland intrusion 
of marine stratus is expected Sun morning. 


Kpdx and approaches...MVFR clouds will remain until 19z...then quickly 
transition from overcast to few-scattered by 21z. VFR conditions expected to 
last from this afternoon through Sunday as offshore flow takes hold. 
Dalton 
&& 


Marine...little change through Monday as high pressure sits offshore... 
and a strong thermal trough remains over SW Oregon. Winds will be 
largely diurnal with strongest winds in the afternoon and evening... 
and slightly weaker winds overnight and early in the morning. Will 
maintain Small Craft Advisory over the coastal waters through Monday. 
Strongest winds will be from Newport southward...especially Sunday 
evening when gusts could approach gale force. Due to strong winds... 
seas will be mainly wind driven. Will likely need a Small Craft 
Advisory for hazardous Sunday afternoon/evening as wave heights climb 
towards 8 to 9 feet range with short periods. Dalton 
&& 


Pqr watches/warnings/advisories... 
or/WA...Small Craft Advisory for winds Cape Shoalwater to Florence 
through Monday. 


&& 


Preliminary point probability of precipitation (probability of measurable precipitation) 
AST ---00 pdx -0000 sle 00000 eug 00000 


$$ 


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.