Area forecast discussion National Weather Service Portland or 200 PM PDT Sat may 25 2013 Synopsis...after a break in rain this afternoon...upper level low pressure brings a wave of rain tonight...lingering into Sunday before tapering to showers later Sunday afternoon. A stronger system should spread more rain across the district on Memorial Day...possibly along with a brief period of breezy conditions along the coast. Brisk westerly flow will keep things unsettled with rain at times through at least middle week. There is a hint that we may dry out by next weekend. && Short term... tonight through Tuesday...our main feature of interest is the upper disturbance pushing inside 130 west around 46 north this afternoon...as the upper low off Puget Sound sound remains stationary through the evening. The main energy associated with this disturbance will push south of the area...but enough will be left to bring a round of widespread rain as these systems amalgamate into one mean upper trough. Low to middle level warm advection in the SW flow ahead of the low as increased the cloud shield offshore and into SW Washington...while surface high pressure...now weakening...has kept this system from making much inland progress elsewhere. Rain has now finally pushed into Astoria. The first low/disturbance will move onshore overnight tonight. Weak flow pattern will result in minimal orographics...and little to no rainshadowing for the Willamette Valley. Additionally...precipitable water values are up around 0.9 in which is above the 75th percentile level for may...or about 130-150% of normal. So again there could be a good bit of steady rain in The Lowlands tonight into Sunday morning. Not expecting the same kind of totals we experienced around Portland the last few days...but this will probably be a heavier event for Salem and Eugene who received less precipitation from the last couple of systems. The upper low will very slowly progress through the area on Sunday...thus expect lingering clouds and rain...with additional energy associated with the low off the Puget Sound sound prognosticated to swing through in the afternoon and evening. There is a bit of question as to whether rain will be steady or more showery Sunday afternoon as the associated upper low moves onshore. NAM bufr soundings show a very moist air mass but little in the way of instability. Regardless temperatures may again have a hard time getting out of the 50s Sunday to near 60 in a cloudy and wet day...though they may spike later in the afternoon in any sunbreaks...as overnight lows will not drop much tonight given clouds spreading in. Kept the middle-shifts trend to keep temperatures several degrees below guidance but did nudge them up a touch. Anywhere that sees a few sunbreaks will warm a bit more into the 60s with the warm late may sun...with the best chance in Lee of the Coast Range and for areas southwest where more ridging attempts to build in. The upper trough will still be working its way through the northern tier Sunday evening...thus some lingering rain/showers mainly before midnight. Precipitation will taper off elsewhere as this system moves east sun evening...as high pressure noses in from the southwest through the afternoon. Should be a bit of break Sunday evening from southwest to northeast...though some rain/showers may linger in the northern tier as the upper low continues to pass through. The break will unfortunately be short lived...as a more organized Pacific frontal system to move onshore later Sunday night or Monday/Memorial Day morning. Depending on the track of this system it may have a brief punch of modest coastal wind with it...but this appears more likely for southern Oregon or northern California where the best jet dynamics will be. The surface pattern looks such that will remain offshore for quite some time...keeping the strongest winds confined to the coastal waters. As a result this system may try to split somewhat as it moves onshore... but still should hold together enough for another pretty good soaking Memorial Day. The upper trough lingers in the area for Tuesday meaning cloudy and periods of rain/showers. Kmd Long term...Tuesday evening through Saturday...cool and showery conditions will continue through much of the work week as several shortwaves wrap around a broad upper level trough. An upper level ridge attempts to build over the Pacific northwest by Friday and early next weekend. This should dry out the conditions over the region starting late Thursday night and Friday...allowing snow levels to rise and temperatures back near normal. Granted there have been decent model discrepancies concerning this potential ridging...but seems like we could see ridging lingering through next weekend. /27 && Aviation...VFR across the region will transition back to MVFR this afternoon on the coast...and this evening further inland. This due to increasing rain as yet another front now about 200 miles offshore pushes inland. Widespread MVFR across region tonight and into sun am... with local IFR conditions after 03z on the coast. Cascades and higher terrain will be obscured in clouds and precipitation. Kpdx and approaches...VFR and dry until later this afternoon. Clouds will thicken after 22z...with occasional rain after 00z. Still looks likely that ceilings will gradually lower. Expect mostly MVFR ceilings...2000 to 2500 feet...after 04z. Little change expected tonight with MVFR ceilings dominating. Rockey. && Marine...front approaching...but gradient not impressive. Will keep south winds 10 to 20 knots...but can not rule out a few gusts to 25 knots. Not enough to warrant any advisories. Front will push onshore early sun am...with winds relaxing. Seas mostly 5 to 7 feet though sun evening. Another front arrives Sun night and Monday. Appears that solid small craft winds of 20 to 30 knots. Seas may briefly clip 10 feet on Monday due to combined seas...but drop back Monday night as wind eases. Rockey. && Pqr watches/warnings/advisories... or...none. Washington...none. Pz...Small Craft Advisory for rough Columbia bar conditions from from 5 am to 9 am sun. && $$ 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.