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fxus66 kpqr 192102 
afdpqr 


Area forecast discussion 
National Weather Service Portland or 
201 PM PDT Friday Mar 19 2010 


Synopsis...a sharp upper level ridge just off the coast will shift 
inland tonight as surface high pressure builds over The Rockies... 
increasing the offshore flow. Low level flow will turn back onshore 
on Sat...ahead of an upper level trough that will move in for sun and 
Monday. High pressure is expected to return briefly around Tuesday...before 
another Pacific system moves through midweek. 
&& 


Short term..visible satellite imagery continues to show mostly clear 
skies over the forecast area...except for a few thin cirrus clouds 
spilling over the ridge. Models continue with similar trends over the 
next couple of days...with the ridge shifting inland tonight and Sat 
while slowly weakening. Strong easterly low level flow will continue 
through tonight...with kpdx-kdls at -4.9 mb. 


A more southerly onshore flow will return Sat as a low ejecting out 
of the longwave trough out over the Pacific lifts to the north beyond 130w. 
This should result initially in a marine surge Sat...during the day 
along the coast...and spreading quickly inland Sat evening. A small 
threat for rain returns by Sat night as weak shortwave energy begins 
to move through...but better chances for rain come on sun as a front 
pushes inland with decent moisture...low level onshore flow...and the 
main trough axis coming in late in the day. Showers will continue 
Monday as the trough moves through the area. Showers will diminish 
likens 


Long term...an upper level ridge will rebuild along the coast 
Tuesday...for a temporary return to dry weather. The ridge will shift 
east across the forecast area Tuesday/Tuesday night allowing the next 
Pacific weather system to approach the coast Wednesday. Rain will 
spread across the County Warning Area Wednesday. Unsettled conditions are possible through 
the end of the week. 


&& 


Aviation...VFR tonight and most of Saturday. Patchy fog and 
stratus moving up along the central Oregon coastline midday 
Saturday. Possible MVFR ceilings along the coast late Saturday 
with the approach of a weak front. 


Kpdx and approaches...VFR tonight and Saturday. Sunset 


&& 


Marine...high pressure over the waters with a thermal trough 
along the coast will give way to a weak disturbance tonight. 
Northeast winds will become easterly and increase and then turn 
southerly later tonight and Saturday with Small Craft Advisory 
speeds. A weak front will move across the waters late Saturday. 10 
feet seas should return Sunday. 


&& 


Pqr watches/warnings/advisories... 
or...none. 
Washington...none. 
Pz...Small Craft Advisory for winds from 2 am Saturday to 11 am PDT 
Sunday for waters from Cape Shoalwater Washington to Cascade Head 
or from 10 to 60 nm. 


Small Craft Advisory for winds from 2 PM Saturday to 11 am PDT 
Sunday for coastal waters from Cape Shoalwater Washington to Florence or 
out 10 nm. 


Small Craft Advisory for winds from 8 am Saturday to 11 am PDT 
Sunday for waters from Cascade Head to Florence or from 10 
to 60 nm. 


&& 


$$ 


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.