074 FXUS66 KPQR 122222 AFDPQR Area Forecast Discussion National Weather Service Portland OR 322 PM PDT Wed Apr 12 2017 .SYNOPSIS...A surface low currently located west of the central OR coast is moving north through the offshore waters today. The low will bring an occluded front through the region during the late afternoon and early evening hours. A period of heavy showers and isolated thunderstorms will accompany the front. Showers will become more scattered later this evening behind the occluded frontal passage. Snow levels will lower overnight and remain below the Cascade passes Thursday and Friday as a cool upper trough moves over the area. Dry weather is expected Saturday and early Sunday before the next system arrives later Sun. The active weather pattern likely continues through at least the first half of next week. && .SHORT TERM...Tonight through Saturday night...An occluding low pres system is located about 220 mi west of Newport this afternoon and is moving north through the offshore waters. The occluded front is very well defined on satellite and is now within 100 mi of the coast. Showers have begun to increase over the past couple hours ahead of the front as surface temps over the interior lowlands have warmed to around 60 deg F, increasing the low level instability. There have also been a couple of lightning strikes detected near the Cascade foothills in Linn and Marion counties. Expect showers will only increase in coverage and intensity as the occluded front moves onshore later this afternoon and taps into the low level instability. The front will move into the Cascades by mid evening, then east of the Cascades by late evening. Showers will continue but come more scattered behind the frontal passage, but will continue through the night. Snow levels have been around 6000 ft or above today, but they will drop sharply later tonight as a colder air mass moves in behind the front. Expect some light accumulations down to the passes overnight, but amounts should remain safely below advisory criteria. The offshore surface low will remain west of the WA waters into Fri, which will bring continued moist onshore flow. There will also be a broad upper level trough over the NE Pac. These features will combine to keep plenty of shower activity going over the Pac NW through the end of the week. The best showers will be on Thu, as the cold pool aloft will be located just to our north. Decided to add a slight chance of thunder to the coastal waters and coast through Thu morning, then extending into the interior during the afternoon. Snow levels will be in the 3500 to 4000 ft range, so expect several inches of snow at the Cascade pass levels and above. However, think road temps will be warm enough to limit impacts to travel. With the low snow levels, and heavier showers have the potential to bring small hail down to the lower elevations. Upper level heights will be rising and the NE Pac surface low will be weakening on Fri. There will still be showers around, but they will be much weaker than those on Thu. They will taper off rapidly Fri evening. Sat looks likely to provide a welcome dry break. A weak upper level ridge will move over the Pac NW. There will likely be some clouds around to start the day, but most locations should see some sun in the afternoon. High temps over the interior lowlands will likely reach near 60 deg. Pyle .LONG TERM...(Saturday night through Wednesday)...The shortwave upper level ridge axis is modeled to move over the Pac NW Sat night. Expect dry weather to last into Sun morning. Then the next low pres system is modeled to push into N Calif and S Oregon during the day Sun. Yesterday the fcst models were keeping the associated precip south of our CWA, but today they have drifted further north. Have increased PoPs across the region Sun afternoon and evening, especially over the southern half of the CWA. However, precip looks to be light, and temps should be a little warmer, into the low 60s for the lowlands. The a broad upper level trough sets up over the NE Pac for the first half of next week. This will continue the trend of mostly cloud, wet, and cooler than average temps. Pyle && .AVIATION...Mainly VFR conditions this afternoon with some occasional MVFR still at the coast. Seeing some TS pop up this afternoon and produce MVFR VIS with moderate to heavy rain. Will continue to see a chance of TS until after sunset, particularly inland from the coast. Otherwise VFR conditions with some gusty winds this afternoon and again Thursday morning. KPDX AND APPROACHES...VFR with showers. Slight chance of TS through this evening. If TS does affect the terminal, expect gusty outflow winds out of the W or SW and heavy rain. Otherwise, moderate offshore flow with occasional gusts to around 20 kt. Bowen && .MARINE...Winds continuing to hover around 20 kt with broad low pressure off the WA/OR/N CA coast. As low pressure moves north, remaining well offshore, it will maintain Small Craft Advisory winds over the local waters through at least Thursday and possibly into Friday. High pres finally builds over the waters Fri night and Sat, for decreasing winds. Seas running 8 to 9 ft this afternoon based on buoy observations and expect them to remain in that range through Friday. Could see a brief 10 ft observation sometime over the next couple of days, but think seas will generally stay below that threshold. Then seas gradually diminish over the weekend, easing to around 5 to 6 ft by Sunday. Bowen && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory for winds until 5 PM PDT Thursday for Coastal Waters from Cape Shoalwater WA to Florence OR out 60 nm. Small Craft Advisory for hazardous seas until 6 PM PDT this evening for Coastal Waters from Cascade Head OR to Florence OR out 60 nm. && $$ Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland 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.