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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Friday
• 
• High: 59 °
• Low: 48 °
• Rain Showers

• Saturday
• 
• High: 64 °
• Low: 52 °
• Chance of Rain

• Sunday
• 
• High: 61 °
• Low: 52 °
• Chance of Rain

• Monday
• 
• High: 63 °
• Low: 52 °
• Mostly Cloudy

• Tuesday
• 
• High: 72 °
• Low: 52 °
• Chance of Rain

Area forecast discussion 
National Weather Service Portland or 
850 am PDT Friday may 24 2013 


Synopsis...the upper low over Washington Friday morning will weaken this 
weekend as it lifts NE into Alberta. A few disturbances will 
continue to rotate around the low...keeping a threat of showers in 
through the weekend with temperatures warming a bit closer to 
normal. An active pattern will continue next week as the flow turns 
westerly...and a series of weak disturbances come in off the 
Pacific. 
&& 


Short term...water vapor pictures showed the upper low over central 
Washington this morning...with the main vorticity lobe lifting north through 
Idaho. A weak surface low was seen just off the coast of kast... 
locally enhancing the low level onshore flow over northwest Oregon. Showers 
on radar and in surface observations appear to be favoring 
orographically enhanced mountains...especially in the north. Will keep showers 
likely today in the north and over the mountains...but given the main 
shortwave lifting the low NE...expect the heavy precipitation threat 
is greatly diminished today. 


Remainder of short term discussion unchanged... 
the upper low will settle over the Canadian rockies for the 
weekend...with a broad upper level troughing pattern over the Pacific northwest. 
Expect off and on shower activity much of the weekend. The best 
chance at any organized precipitation appears to be Sat night into 
early sun...as the models all show a shortwave or weak closed low 
pushing into the Pacific northwest. Temperatures should continue to rebound...as we get 
more sunbreaks and the airmass moderates. Inland sites should get 
into the middle 60s on both Sat and sun. 


Another more organized system is being advertised on Monday. There is 
plenty of model uncertainy with this system...with some model runs 
stretching the upper level forcing and keeping the bulk of it to our 
south. However...it appears that we will have a decent shot at 
widespread...albeit light...precipitation. Decided to go with likely 
probability of precipitation later Monday as most models are bringing precipitation into our forecast area. 
Pyle 


Long term...no changes. Previous discussion follows... 
westerly flow aloft likely to be persist through the early part of 
the week. This will keep region under a persistent chance for rain as 
a series of shortwaves moves through. The westerly flow off the 
Pacific will keep temperatures moderated...likely a little below 
seasonal averages. Models tend to diverge some late in the week with 
GFS and Canadian cutting off an upper low offshore. Bottom line 
though is for a continuation chance of rain. 
&& 


Aviation...weak low pressure lingering offshore will maintain a 
moist air mass and weak flow over the area today. This will allow 
showers and local IFR/low MVFR ceilings to remain at the coast and 
inland through 18z. Increasing S-SW flow is expected to bring ceilings 
above 2000 feet by midday. However occasional showers will reduce ceilings 
from time to time...especially at the coast where ceilings look to 
remain IFR/low MVFR through the day. 


Kpdx and approaches...weak flow and moist air mass will maintain 
occasional MVFR showers through 18z. Increasing S-SW flow should 
raise ceilings above 2000 feet by midday...with VFR in scattered showers 
expected this afternoon. Weagle/Burgess 


&& 


Marine...no updates. Seas hovering around 8 to 9 feet this morning 
will begin to relax this afternoon as low pressure off Astoria moves 
inland and northwest fetch dies down. Seas will continue to subside to 
around 6 feet by tonight...and remain less than 6 feet through Sunday. 


Some gusts to 20 knots reported in mainly the southern waters should 
ease today/tonight as the low pressure system weakens and weak high 
pressure builds over the waters. A weak low pressure system will move 
across the Oregon waters late Sat/early sun...but winds should 
generally stay below 25 knots. A more organized system is possible 
for Monday which could produce a brief coastal jet for gusts 30 to 35 
knots...but this depends on the track. There is still some 
possibility this system could focus more on southern Oregon and northern 
California than our waters. 


Morning ebbs remain very strong due to the full moon...so expect 
rough Columbia River bar conditions the next couple mornings. 
Weagle/Burgess 


&& 


Pqr watches/warnings/advisories... 
or...none. 
Washington...none. 
Pz...Small Craft Advisory for rough Columbia River bar from 4 am 
to 8 am PDT Saturday. 
&& 


$$ 


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.