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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 59 °
• Low: 48 °
• Rain

• Thursday
• 
• High: 59 °
• Low: 46 °
• Rain Showers

• Friday
• 
• High: 64 °
• Low: 43 °
• Chance of Rain

• Saturday
• 
• High: 77 °
• Low: 45 °
• Partly Cloudy

• Sunday
• 
• High: 81 °
• Low: 52 °
• Chance of Rain

Area forecast discussion 
National Weather Service Portland or 
202 am PDT Wednesday Jun 19 2013 


Synopsis...upper level low that has been lingering off the 
Washington and Oregon coast for the past several days is now moving 
inland. This will bring cool and showery weather today with a low 
threat for thunderstorms over the Cascades. Showers will gradually 
taper off Thursday and Friday as the upper low lingers over eastern 
Washington. The weekend warmup is looking less likely with recent 
model runs...in fact some models are bringing in a Pacific frontal 
system for more rain possibly on Sunday. 


&& 


Short term...scattered showers continue to rotate around the upper 
low now nearing the coast early this morning. The low is forecast to 
shift over the forecast area today for continued showers in the 
unstable air mass. Model soundings begin to stabilize the upper 
levels in the afternoon. This should limit vertical growth of showers 
so charge separation can not occur. However stabilization over the 
Cascades should be a little later and combined with the high terrain 
may provide the additional lift needed to produce thunderstorms. As 
a whole cooler than normal temperatures with showers today. 


By Thursday the trend has been for slower movement of the 
system...with it lingering somewhere over the middle-Columbia Basin 
Thursday. With this proximity there will be the continued threat of 
wraparound moisture and showers. By Friday the low is further east 
lowering the threat for showers and high temperatures approaching 
seasonal normals. 




Long term...Friday night through Monday...given the last couple of 
model runs we are starting to lose confidence in our weekend ridging 
and warmup. The upper low festering over the middle-Columbia Basin now 
appears to linger into Friday...not really allowing the upper ridge 
to build in full force before the next Pacific frontal system 
approaches for the weekend. There are a couple factors to consider 
here. There is a historically strong upper level ridge over Alaska... 
with our upper low stuck below it in a Rex block pattern. The 
tendency will be for the Pacific jet to try to undercut the alaskan 
ridge this weekend and this is what the models are beginning to show. 
Additionally the Madden-Julian oscillation seems to be entering its 
most active phase since February...which is impressive for June. All 
this points to a wet week next week...so we significantly trended 
probability of precipitation upward and cooled off temperatures beginning Sunday. Weagle 


&& 


Aviation...mostly VFR this am...but do have areas of MVFR and 
localized IFR ceilings on central Oregon coast. These conditions will 
spread north along the coast with mix of MVFR and brief VFR this am. 
Further inland...VFR. But do have areas of MVFR ceilings from Cowlitz 
valley S to kpdx and kttd...and along S Washington/north or foothills. These 
lower clouds will back build from the Cascades and cover a large 
part of the interior...mainly between 10z and 19z. Ceilings should 
break up after 19z...with mix of VFR and localized MVFR with the 
scattered showers. 


Kpdx and approaches...MVFR ceilings have formed across the area as 
rain cooled air from east arrived. Worst conditions to north and east of 
kpdx at moment...as areas to S and west are VFR. MVFR ceilings will 
spread across rest of Ops area through 14z...and persist through 
at least 18z. 
&& 


Marine...little change as a broad area of low pressure offshore will 
continue to slowly track toward the coast through Wednesday. Winds 
generally 10 to 15 knots. Seas will remain at 3 to 5 feet through Sat. 
&& 


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.