958 
fxus66 kpqr 211502 
afdpqr 


Area forecast discussion 
National Weather Service Portland or 
801 am PDT sun Mar 21 2010 


Synopsis...a cold front moving through the region this morning will 
be followed by an upper level trough tonight. High pressure will move 
across the Pacific northwest Tuesday...then another Pacific system is 
expected around middle week. 


&& 


Short term...baroclinic zone and rain moving across the region this 
morning. Shower will follow this afternoon as the upper trough 
approaches and a vorticity maximum passes through. 


Fairly decent orographic flow for snow in the Cascades...but moisture 
is limited in the cold air with not very strong dynamics. So...snow 
amounts below advisory levels. 


Models in good agreement through the short term. Another vorticity 
maximum passes through by middle day Monday with showers tapering off. 
Big upper ridge on Tuesday with surface high inland and a bit of a 
thermal trough along the coast for some warming. Sunset 


Long term...no changes. Previous discussion follows... 
GFS and European model (ecmwf) similar through middle week...then diverge a little on 
amplitude and phase by the end of the week. Will follow the GFS 
through the extended period with below climatology probability of precipitation late in the 
period. Sunset 


&& 


Aviation...strong onshore flow. Mostly a mix of VFR with areas of 
MVFR ceilings and light rain...expanding across the region later this 
morning. Worst conditions over the Coast Range and along the 
coast. After 21z...expect showers and mostly VFR...but lingering 
MVFR over Cascades will keep mountains and passes frequently obscured through 00z. 


Kpdx and approaches...MVFR with occasional rain/showers thru19z. 
Ceilings will turn to a VFR-MVFR mixture after 21z. 


&& 


Marine...front now slowly moving along the coast...and will 
continue moving onshore today. Will allow Small Craft Advisory 
to expire at 18z due to decreasing S to SW winds. Seas now around 
10 feet...and will hold near 10 to 11 feet today...but will fall below 
10 feet later this evening. 


&& 


Pqr watches/warnings/advisories... 
or...none. 
Washington...none. 
Pz...Small Craft Advisory for winds until 11 am PDT this morning for 
coastal waters from Cape Shoalwater Washington to Florence or out 60 nm. 


Small Craft Advisory for hazardous seas until 11 PM PDT this 
evening for coastal waters from Cape Shoalwater Washington to Florence 
or out 60 nm. 


Small Craft Advisory for rough Columbia River bar until 11 am 
PDT this morning for Columbia River bar. 


Small Craft Advisory for rough Columbia River bar from 7 PM to 
11 PM PDT this evening for Columbia River bar. 


&& 


$$ 


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.