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.