063 
fxus66 kpqr 232145 
afdpqr 


Area forecast discussion 
National Weather Service Portland or 
245 PM PDT Wednesday Jul 23 2008 


Synopsis...an upper level ridge will move over the Pacific northwest 
tonight and continue over the area Thursday for dry and a bit warmer 
weather. Another upper trough will set up off the coast for Friday 
through early next week with a series a disturbances moving through. 
The main effect will be to increase the onshore flow again. 
However...a weak frontal boundary will move onto the coast Friday 
night and Saturday morning and produce a little drizzle especially 
near the coast. There is not a lot of change in the main pattern into 
next week. 
&& 


Short term...water vapor satellite imagery shows the main impulse 
with the current upper trough is mostly east of the Cascades this 
afternoon...with clouds breaking up across northwest Oregon from the 
south. There is still a decent onshore push up along the Columbia 
River where clouds are more solid...but these too should break up in 
the late afternoon and early evening and generally clear overnight. 
We will be seeing the inversion reforming closer to the surface 
overnight and see lower deck of stratus and patchy fog form tonight 
near the coast and possibly push a bit down the Columbia River early 
Thursday. But then Thursday should be a nice and a bit warmer day 
with more sunshine as the upper ridge behind the exiting system is 
over the area. Inland temperatures should make it to near or a bit over 80. 


The next upper trough approaches Thursday night and Friday with 
onshore flow picking up again late Thursday and Friday. Night and 
morning low clouds still look as though they will mainly push through 
the coastal gaps Friday morning and then clear back to near the coast 
in the afternoon with inland temperatures back down a couple of degrees to 
near normal. There is a weak frontal boundary with this upper trough 
that tries to push to near the coast Friday night and Saturday and 
should increase the clouds at the coast and even inland with possibly 
a little drizzle at the coast and along the coastal mountains. The 
clouds may not clear much Saturday afternoon even inland. Tolleson 


Long term...the upper trough from late in the short term period is 
still around early in the extended period...with a short wave moving 
through Saturday night that could produce a touch of drizzle near the 
northern mountains. May see a bit more sunshine Sunday afternoon 
inland but temperatures will be tough to reach normal. Have left the 
remainder of the extended alone...which reflects near normal temperatures 
and a moderate onshore flow for late night and morning low clouds. 
The GFS model looks too strong on a system early next week...while 
the European model (ecmwf) is much warmer...and opted for a middle of the Road 
solution that is dry but near climatology. Main message is models maintain 
a westerly flow aloft for a while that encourages some onshore flow 
with the weather near normal. Tolleson 
&& 


Aviation...generally clear inland with a few VFR ceilings in the extreme 
north part of the area and along the coast. Inland cloud cover will 
continue to dissipate through 03z and after 08z MVFR ceilings will move 
inland along the Columbia River reaching kkls about 12z...and to kpdx 
around 15z. At the coast...VFR through about 03z then lower MVFR ceilings 
will begin to reform along the shore...with fairly solid MVFR ceilings 
after 06z. 


Kpdx and approaches...VFR ceilings will dissipate by 23z...then VFR 
conditions will prevail through the night. After 14z a few MVFR ceilings 
may develop due to marine stratus...but they will burn off by 17z. 
&& 


Marine...high pressure over the coastal waters weakens slightly Thursday 
as a weak front approaches from the west. On Friday the high weakens 
significantly and shifts east as the very weak front moves over the 
coastal waters. High pressure rebuilds Sat and another front approaches 
the coastal waters late sun. Seas remain below 10 feet for the 
foreseeable future. Dk2 
&& 


Pqr watches/warnings/advisories... 
or/WA...Small Craft Advisory for winds from Cascade Head to Florence 
through this evening. 


&& 


Preliminary point probability of precipitation (probability of measurable precipitation) 
AST --1122 pdx 00---1 sle 0000-1 eug 0000-- 


$$ 


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.