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.