838 
fxus66 kpqr 220439 
afdpqr 


Area forecast discussion 
National Weather Service Portland or 
830 PM PST Friday Nov 21 2008 


Synopsis...a vigorous Pacific cold front is pushing across the area 
this evening with rain and mountain snow. Snow levels will fall below 
Cascade Pass levels tonight...with a couple of inches of snow 
accumulation expected on the passes by Saturday morning. High 
pressure will build across the district Saturday...causing showers to 
decrease. Gusty east gorge winds will be possible again Sunday and 
Monday as high pressure moves east of the Cascades. Region stays 
mainly dry Monday...then the next cold front brings another chance of 
rain for Tuesday. Long range models are hinting at a chance of rain 
again for Thanksgiving day. 


&& 


Short term...a vigorous cold front will continue to move across the 
area this evening with rain and High Mountain snow. Snow levels are 
currently above pass level...but will come down overnight as cooler 
air moves in behind the front. A couple inches of accumulation are 
likely on the passes...but for now it appears accumulations will 
remain below advisory criteria. 


High pressure builds in quickly Sat...shutting off the orographic 
flow for the Cascades. This should allow showers to taper off quickly 
and a rather dry afternoon throughout. Sat night looks to be another 
mainly clear calm night...so fog and near freezing temperatures will 
again be a possibility for the outlying valleys. Gradients turn 
offshore Sunday...causing another easterly wind event especially 
through The Gorge. Dry weather and gusty east gorge winds may linger 
into Monday as strong ridge remains over the interior northwest. 


Long term...no changes. Previous discussion follows... 
models show a split upper level flow pattern over the region at times 
during the extended. Did not change the forecast too much as timing 
is often an issue with these types of patterns. The 12z GFS and Euro 
both pinch off a portion of an upper level trough Monday evening and 
form a cut off upper level low off the coast of California. The 
result is a weakening front that moves through the region on Tuesday. 
Another strong upper ridge will build in Wednesday and give dry conditions 
to the forecast area. Another trough approaches the Pacific northwest on 
Thursday night. Dalton 


&& 


Aviation...cold front along the coast will track inland late this 
evening. Conditions generally VFR but dropping to MVFR at times as 
frontal passage occurs as well as during some of the stronger Post 
frontal showers. Occasional IFR conditions possible near the coast. 
Gusty south winds will increase inland between 06z and 08z while S 
to SW winds at the coast shift to the west. Patchy fog and low 
clouds may develop towards morning but the unstable air mass should 
limit the aerial extent. 


Kpdx and approaches...mainly VFR conditions with temporary drops to 
MVFR with frontal passage around 06z. Gusty S to SW winds 06z to 08z 
then showers and winds both diminishing through the early morning 
hours. Patchy fog possible around sunrise. Ruthford. 


&& 


Marine...with the front inland along the Washington coast and northwest tip of 
Oregon the strong south winds have shifted to the west and 
diminished to Small Craft Advisory levels...25 to 30 knots. A weak 
frontal wave offshore 
of the central Oregon coast is slowing the fronts progress inland in 
that area. Winds will continue to diminish overnight dropping to 
around 15 knots by 4 am. Seas will increase to 15 to 17 feet later this 
evening and remain in the middle teens overnight and into Sat morning. 
Seas will remain above 10 feet until Sun morning. Ruthford. 


&& 


Pqr watches/warnings/advisories... 
or/WA...Small Craft Advisory for rough Columbia River bar through 
Sat afternoon. 
Small Craft Advisory for hazardous seas Cape Shoalwater to 
Florence through early Sun morning. 
Small Craft Advisory for winds Cape Shoalwater to Florence 
through 4 am Sat morning. 


&& 


$$ 


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.