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Area forecast discussion 
National Weather Service Portland or 
150 am PDT Monday Mar 22 2010 


Synopsis...an upper trough will move across the region today. Low 
level onshore flow will weaken today...and turn offshore by Tuesday as a 
surface high pressure system moves inland. Another low pressure 
system will approach the region late Wednesday...and move in by Thursday. 


&& 


Short term...radar shows showers continuing to move across the 
forecast area early this morning. Water vapor pictures show a short 
wave near 127w...on the backside of the upper trough. After this 
moves inland later this morning...expect showers to drop off as low 
level flow turns more northerly as surface high begins to push in. 


Models remain in good agreement through the short term...depicting a 
ridge moving across the region tonight and Tuesday. As low level flow 
turns easterly air mass to dry and warm. The dry and mild weather 
continues into Tuesday night and Wednesday with continued offshore flow. By 
Wednesday though should see upper level clouds beginning to spread in as 
the flow turns to the SW. On Wednesday models suggest a return to 
southerly low level flow...which would bring marine air back to the 
coast...along with perhaps some low clouds. 


Long term...no changes. Previous discussion follows... 
the GFS and European model (ecmwf) are in general agreement through much of the week. 
Quick moving shortwaves rotate through the forecast area every 36 to 
48 hours through the end of the week...bringing periods of 
precipitation and keeping temperatures near climatology. Brown 


&& 


Aviation...mostly VFR conditions with moderate onshore flow...with 
pockets of MVFR ceilings around the showers. Worst conditions remain 
over the Coast Range and Cascades where mountains are frequently obscured. 
Not much change through 18z...then showers gradually ending as weak 
high pressure builds offshore...with VFR expected most areas. 


Kpdx and approaches...mostly VFR ceilings today...with brief MVFR ceilings 
around 2500 to 3000 feet through 18z as stray Showers Pass in and near 
the area. VFR clouds break up more after 04z tonight. 
&& 


Marine...winds remain under 20 knots through Wednesday...with seas mostly 6 to 
8 feet...with highest over the outer waters. No advisories for today 
or Tuesday. Next system that brings winds and seas up some is expected 
to arrive late Wednesday night. 
&& 


Pqr watches/warnings/advisories... 
or...none. 
Washington...none. 
Pz...none. 


&& 


$$ 


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.