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fxus66 kpqr 210410 
afdpqr 


Area forecast discussion 
National Weather Service Portland or 
809 PM PST Friday Nov 20 2009 


Synopsis...residual showers will continue the remainder of the night 
after the passage of a cold front. Another front approaches later 
Saturday...with strong winds possible on the coast and 
significant snow expected in the Cascades. The next storm arrives 
later Monday. 
&& 


Short term...still considerable showers this evening...especially 
along the Cascades and will keep the advisory for snow. A warm front 
approaches Saturday with increasing winds along the coast consistent 
with high wind watch. 


The trailing cold front gets slowed by a wave with another low 
developing. The lows pushes to the coast Saturday night. All the 
models have varied solutions...many of which would result in 
significant winds in the interior at first look. But...the upper 
trough becomes negatively tilted...somewhat more in the NAM than the 
GFS...with momentum transferring south. Not good for a strong 
southerly push of winds. Also the surface low is filling as it moves 
inland and the low is not moving north or north northeastward 
allowing the strong up valley push of winds. 


So will wait to see if we get a better and more consistent look on 
later runs on dealing with the winds. With that second wave slowing 
things down...will expand the Winter Storm Watch to cover all day 
Sunday in the Cascades rather than just the morning. Sunset 


Long term...no changes. Previous discussion follows...weak high pressure 
builds over the forecast area Monday night. 
Models show a weak system approach the coast early Tuesday...but it 
tracks further north and lightly brushes the far northwest corner of 
the County Warning Area. This ridge is more persistent than previous model runs 
suggested. It manages to delay the arrival of a second system 
through Thursday. By middle next week...models disagree on the solution for 
the weekend. GFS model runs are inconsistent...the 06z run held back 
on precipitation through Thursday night but the current run shows rain 
extending to the Cascades Thursday night. So far...models suggest a 
fairly nice weekend as another upper high pressure temporarily sets up 
over the Pacific northwest. Lramirez 


&& 


Aviation...cool showers continue to stream in off the Pacific this 
evening in unstable westerly flow. VFR conditions are expected 
across all areas tonight with a 40% chance of MVFR conditions in and 
near showers. A warm front will bring rain and MVFR conditions to 
the coast and Coast Range by midday Saturday. 


Kpdx and approaches...conditions are expected to remain primarily 
VFR tonight with a 40% chance of MVFR conditions in and near 
showers. VFR conditions are expected Saturday. 


&& 


Marine...small craft winds will continue through Saturday morning 
before the next stronger front boosts gusts to low end gale criteria 
Saturday afternoon with the possibility of another wave generating 
strong gales and possibly storm force winds by late Saturday night 
into Sunday morning. Seas currently hovering around 12 feet and should 
build to 16 to 18 by Saturday night. 


&& 


Pqr watches/warnings/advisories... 
WA/OR...Small Craft Advisory for rough Columbia River bar 
through Sat evening. 
Small Craft Advisory for winds Cape Shoalwater to 
Florence through Sat morning. 
Small Craft Advisory for hazardous seas Cape Shoalwater to 
Florence through Sat morning. 
Gale Warning Cape Shoalwater to Cascade Head Sat morning 
through late Saturday night. 
Gale Warning Cascade Head to Florence Sat morning through 
Saturday evening. 
Storm watch Cascade Head to Florence Sat evening through 
Sunday morning. 
Snow Advisory for the South Washington and north Oregon 
Cascades through Sat morning. 
Winter weather watch for snow for the South Washington and 
north Oregon Cascades and the Cascades in Lane County for 
Saturday afternoon through Sunday. 
High wind watch for the northern and central Oregon coast 
for Sat afternoon and night. 
&& 


$$ 


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.