Area forecast discussion National Weather Service Portland or 320 am PDT Wednesday may 22 2013 Synopsis...a cold upper low will remain anchored over the Pacific northwest for the remainder of the week...keeping a cool showery weather pattern in place for the next few days. The low will weaken over the weekend...reducing the chances for showers...and allowing temperatures to warm back closer to normal. && Short term...an upper level low with a couple of shortwaves pin-Wheeling around it will drive the weather through Friday. The weather pattern will be fairly persistent with showers and unseasonal cool temperatures being the dominant features. The showers will become enhanced this afternoon...especially over the mountains and may have periodic short bursts of locally heavy rain. Models hint of weak instability across the region each day but think the best chance for thunderstorms remains outside of the Portland forecast area. Snow levels will remain around 3 kft today..then gradually rise Thursday and Friday. Snow levels should rise above pass level on Friday. Expect an additional 1 to 3 inches of snow above 3000 feet today. Long term...the low will weaken on Friday but linger around over the area through the weekend. Models are trying to bring a shortwave ridge over the area briefly on Monday...but moist onshore flow will prevent total drying. Another storm is expected early next week...Monday night or Tuesday. && Aviation...mostly VFR conditions currently with scattered shower activity across the region this morning. Expect shower activity to increase after 12z...with periods of MVFR ceilings at times during heavier showers. A disturbance embedded in the large scale upper level low will bring steadier rain during the late morning and afternoon hours. Expect more widespread MVFR conditions from roughly 18z through 00z. Then the trend will be toward VFR this evening as shower activity diminishes. Kpdx and approaches...mainly VFR in scattered showers. A brief period of MVFR ceilings possibly later this morning in any heavier showers...mainly after 12z. Predominant MVFR conditions more likely from 18z to 00z as showers become steadier. Trend will be toward VFR during the late afternoon/evening as showers diminish. Pyle && Marine...west to northwest winds of 15 to 20 knots with periods of gusts to 25 knots to continue through Wednesday. The forecast models indicate the strongest gradient will be confined to the outer waters...with less wind near shore. Decided to drop the Small Craft Advisory for the inner waters. Winds will decrease late Wednesday and the trend will be toward more benign weather late this week into next weekend as the upper low weakens and higher surface pressure builds into the waters. Increased the forecast seas by a couple feet this morning as the forecast models have been running a bit too low compared to observations overnight. Expect seas should generally hover in the 11 to 14 feet range through Wednesday. Seas will begin to gradually subside Thursday...dropping below 10 feet by midday Thursday. Seas will continue to gradually subside...reaching 5 feet or lower over the weekend. Pyle && Pqr watches/warnings/advisories... or...none. Washington...none. Pz...Small Craft Advisory for winds until 5 PM PDT this afternoon for Waters from Cape Shoalwater Washington to Cascade Head or from 10 to 60 nm-waters from Cascade Head to Florence or from 10 to 60 nm. Small Craft Advisory for hazardous seas until 5 PM PDT this afternoon for coastal waters from Cape Shoalwater Washington to Florence or out 60 nm. Small Craft Advisory for rough Columbia River bar until 5 PM PDT this afternoon. && $$ 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.