Area forecast discussion National Weather Service Portland or 230 PM PDT Thursday may 23 2013 Synopsis...an unseasonably cold upper level closed low will remain over the Pacific northwest into Friday...continuing to wrap moisture around much of southwest Washington and northwest Oregon. The low will begin to move east Friday and the precipitation will break up into a more showery pattern. Temperatures will warm a bit over the weekend...but a chance for showers will remain as weak energy moves through. A couple of systems are expected next week for more precipitation chances. && Short term...the upper low that has been over the Pacific northwest the past couple of days was still over western Washington early Thursday afternoon. A short wave rotating around the low was pushing SW off the North Washington coast...with radar showing a large area of rain ahead of the shortwave extending from off the Washington coast into northwest Oregon. As this wave swings around the low and through Oregon overnight...should see rain increase again over most of the area overnight. Models with this system have tended to underestimate rainfall amounts...but seem to have have adjusted somewhat with the latest run. Once this wave moves through...models indicating the the main part of the upper low lifts NE towards southern Alberta Friday. To varying degrees models suggest a weaker shortwave still on the backside of the low Friday...so will leave likely probability of precipitation in through Friday. After that...a few more shortwaves still expected Sat into sun...the most prominent of which pushes inland S of the forecast area Sun morning. A modest onshore flow persists through the period...necessitating the includion of probability of precipitation through the weekend. Long term...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...ceilings have improved a bit this afternoon...with MVFR mostly along the coast and far north interior and VFR elsewhere. However as upper low of Washington coast drifts a bit to the S and SW tonight...should still see rain and MVFR conditions spread across the region this evening and tonight. Steady precipitation ends later tonight but moist air mass still supporting quite a bit of MVFR ceilings. Will see conditions become VFR over most areas on Friday with scattered showers. Cascades frequently obscured through tonight. Kpdx and approaches...mix of VFR and MVFR until 00z or 01z...then will have increasing MVFR ceilings as rain increases. Ceilings improve a bit later tonight...but still higher end MVFR. Rockey. && Marine...seas were still bouncing between 9 and 10 feet...but will continue to subside tonight and Friday. Broad low pressure stalled off the Washington coast and weak pressure gradients...so winds mostly 15 knots or less. Low pressure will move inland and weaken Friday and Sat. The next system could increase winds/seas later sun or Monday...but still uncertainty on the track and strength of this system. No changes for now...as looks to be decent potential for 20 to 25 knots southerly winds with that front. Rockey. && Pqr watches/warnings/advisories... or...none. Washington...none. Pz...Small Craft Advisory for rough Columbia bar conditions until 6 PM today...and again between 3 am and 8 am Friday. && $$ 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.