Area Forecast Discussion
Issued by NWS Portland, OR

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000 FXUS66 KPQR 160946 AFDPQR Area Forecast Discussion National Service Portland OR 245 AM PDT Tue Jul 16 2019 .SYNOPSIS...Plenty of clouds around the region this week, with some chance of showers. Highest chance of precipitation will be later Wed night into Thu morning as a decent front moves across the region. Unsettled weather continues on Fri into early Sat, then rest of next weekend looks mild and dry. && .SHORT TERM...Today through Thursday...Onshore flow over the region continues, with plenty of clouds. Still have rather deep marine layer over the region, which should help support spotty drizzle this morning, mainly along the coast, and inland against the Cascades foothills. Remnants of weak surface low still just off the Oregon coast this morning. With bit of instability still over the region, will keep a minor chance of showers (PoPs of 20 pct or less) for today. Another upper disturbance off the Alaskan panhandle will slide southeast tonight and Wed, then shift inland over Washington Wed night and Thu. During the time, the low will bring a slowly moving warm front across the region later Wed, followed by a cold front later Wed night. Currently, there is decent slug of mid and high level moisture over the north Pac, roughly along 50 deg N, and out between 140 and 160 deg W. Models continue to show this moisture getting entrained into the prior mentioned frontal system. All said, will see light rain develop along the coast Wed afternoon with the warm front, while most all others stay mostly dry. However, with the cold front arriving, rain along the coast will gradually spread southward and inland Wed night. Though not a big rainmaker, likely to see 0.15 to 0.30 inch in the Willapa Hills, northern Coast Range, and Cascades as far south as Mt Jefferson. Generally less than 0.10 inch elsewhere. Models fairly insistent that the front will shift east of the Cascades early Thu am, with rain quickly transitioning to showers. Air mass not all that unstable behind the front, so dynamic forcing not impressive. Will keep with decreasing chance of showers, for mid to late morning through early evening on Thu, but have feeling even that may be too much PoP for most areas. /Rockey .LONG TERM...Thursday night through Saturday...Few showers will linger into Thu evening, especially over the higher terrain. Cooler temperatures will be most noticeable at night due to the drier air mass, and some outlying areas may dip into the upper 40s. Now appears the extended models, both GFS and ECMWF, are swinging yet another upper low out of the coastal British Columbia area and into the Pac NW for Fri. This will bring more clouds, along with some minor chance of showers to the region, and locally breezy west to northwesterly winds over the higher terrain. Then, high pres build over the weekend, with milder and drier weather. /Rockey && .AVIATION...A weak upper trough over the area will continue next few day with somewhat unsettled conditions. Light onshore flow will continue to bring cloudiness in the area. Inland...expect VFR conditions to prevail with cigs 4000-7000 ft. But there will be occasional MVFR cigs around 2500-3000 ft through about 16-18Z. At the coast...MVFR to IFR conditions likely to persist through 18-20Z, but some of the guidance shows conditions may not improve above MVFR. But in either case increasing onshore flow ahead of the front for Wed, will bring MVFR conditions again after about 04Z Wed. KPDX AND APPROACHES...MVFR cigs 2500 feet are filling in the areas. Cigs should then improve to VFR by 18Z with a BKN deck with cigs 4000 to 5000 feet persisting through Tue evening. && .MARINE...A ridge of high pressure over the waters shifts inland tonight ahead of a front arriving Wednesday. Models have been fairly consistent with the timing of the front, moving ashore Wed afternoon. But differ on the strength of the winds, for now only the NAM based models are indicating wind gusts to around 25 kt over the northern zones. Based on this have held winds below advisory criteria and will see if other models come on board with NAM solution. High pressure begins to rebuild offshore on Thursday and strengthens for the weekend. This will result in a return to northerly winds through at least early next week. Gusts 25-30 kt can be expected for the weekend with the strongest winds beyond 10 NM offshore. Seas start in the 2 to 4 ft range, then build to around 7 feet Thursday morning. The larger seas are a product of the increased wind wave height from the short wave system that moves through Wednesday night into Thursday but also from a 6 ft swell out of the NW that will be the dominant swell throughout the forecast time period. /mh/BPhillips && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ 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. This area is commonly referred to as the forecast area.

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