912 
fxus66 kpqr 221017 
afdpqr 


Area forecast discussion 
National Weather Service Portland or 
215 am PST Sat Nov 22 2008 


Synopsis...front over Oregon Cascades early this morning will push 
east of area by daybreak. Northwest flow aloft over area today will 
lift further north this afternoon. This will allow surface high 
pressure to build into the north Oregon coast by late afternoon 
brining drier northwest flow to the south part of the area. High 
pressure will shift inland overnight turning onshore flow offshore 
after midnight. High pressure over Idaho on Sunday and Sunday night 
will give moderate offshore flow to area. Pacific front approaching 
the area will split apart offshore on Monday as high pressure holds 
over Idaho. Next Pacific front fairly weak will effect the area on 
Tuesday. The main jet flow will continue to split as it approaches 
the coast for the rest of the week. Another system will move into 
this split flow and may effect the area on Thursday. 


&& 


Short term...front early this morning over Oregon Cascades trailing to 
near keug will move into central Oregon by daybreak. Will leave likely 
showers Oregon Cascades for early morning before dawn until front passes 
east. Northwest flow aloft over area behind front. Short wave approaching 
coast early this morning. Showers have decreased ahead of short wave 
but will increase again especially north as initial short wave move in 
this morning. Next short wave in northwest flow will move into northwest Oregon/SW Washington 
this afternoon. With flow lifting north during the day shower threat from 
second short wave will be confined to north part this afternoon. High 
pressure reaches north Oregon coast by late afternoon. This will allow drier air 
to reach S part of area allowing some clearing. High pressure shifts 
inland overnight. Onshore flow in the north during the evening turns offshore 
for Alabama the area after midnight. Offshore flow still weak by Sun 
morning especially for valley areas. This will allow areas of fog to 
form later Sat night and continue into Sun morning. Offshore flow 
increases during sun as high pressure strengthens over Ida and Pacific front 
approaches offshore. Still inland valleys especially S will have 
difficulty clearing the fog/stratus and will go with slow partial 
clearing there. Upper ridge holding over rockies Sun night and Monday. 
This forces jet to split offshore taking main energy of front 
offshore S into California. Offshore flow continues Sun night then weakens 
some Monday afternoon. Southern inland valleys will see fog redevelop 
Sun night with slow clearing again on Monday. Kosovitz 


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...wide range of flight conditions early this morning. 
Generally VFR at most inland taf sites...but areas of MVFR and IFR 
ceilings due to residual low-level moisture. Another short-wave 
disturbance nearing the coast as of 10z. This will likely bring a 
renewed threat of showers and potential MVFR or lower conditions 
through the morning hours. Onshore low-level flow throughout the day 
will keep a threat of MVFR ceilings at all taf sites. High pressure aloft 
and at the surface strengthens over SW Washington and northwest Oregon after 06z 
sun...which will likely result in areas of fog away from The Gorge. 
Expect offshore gradients to increase through The Gorge between 06z 
and 12z sun. 


Kpdx and approaches...VFR at the moment...but areas of MVFR or IFR 
ceilings in outlying areas...such as khio...kspb and kttd. There is a 50 
percent threat that ceilings at kpdx could drop to MVFR in -shra through 
18z. Expect VFR to prevail after 18z. East to southeast wind should 
develop around 06z sun to prevent fog formation. Weishaar. 


&& 


Marine...will drop the Small Craft Advisory for wind with this 
package as all reporting sites were 15 knots or less as of 10z. 
However...small craft for hazardous seas and rough Columbia bar 
will continue through 12z sun. Low confidence in forecast Tuesday and 
beyond. GFS and European model (ecmwf) split system off the coast Monday and take the 
main portion down the California coast...leaving the waters in some 
sort of northwest to north flow. Weishaar. 


&& 


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