Area Forecast Discussion National Weather Service Portland OR 914 PM PDT Sat Mar 25 2017 .SYNOPSIS...Showers will continue to decrease overnight tonight as onshore flow decreases. The next rather strong frontal system will spread rain into southwest Washington and northwest Oregon fairly early on Sunday that will continue through the day. Look for breezy conditions as well with snow in the Cascades. The associated cold front will move onshore and through southwest Washington and northwest Oregon late on Sunday. Onshore flow behind the front will keep showers spreading onshore across the area through Sunday night and Monday, with snow levels below the passes in the Cascades. A system will brush the northern parts of the forecast area with precipitation Tuesday, followed by another Wednesday and Thursday that will affect all of the area. We may see some drying towards the end of next week. && .SHORT TERM...(Tonight through Tuesday)...Onshore flow was turning more southerly and weakening tonight with just a few showers remaining over the forecast area. These will continue to decrease overnight before the approach of the next system. The models show the next rather strong system approaching late tonight, spreading rain and Cascade snow across southwest Washington and northwest Oregon fairly early on Sunday and continuing through most of the day Sunday. The associated cold front comes onshore and moves through the forecast area late Sunday. It will be windy along the coast ahead of the front, and breezy inland. Snow levels in the Cascades will start out below the passes Sunday morning, may rise up to near or just above the passes in Oregon in the afternoon, then fall back below the pass elevations Sunday night and Monday as onshore flow behind the front spreads plenty of showers across the area. Have issued a snow advisory for the Cascades for Sunday through Monday for all of this. From 6 to 14 inches are possible through Monday, with the higher amounts at elevations above the Cascade passes. Showers decrease Monday night as the onshore flow decreases. The models are coming in better agreement that the next system will mainly go into western Washington on Tuesday, brushing the northern half of our forecast area. Tolleson .LONG TERM...No Changes. Previous discussion follows... (Tuesday night through Saturday) Upper-level pattern becomes more amplified later next week, behind a trough that will bring more rain Tuesday night into Wednesday, transitioning to showers on Thursday. This means a ridge builds up over the Pacific Northwest Friday for a dry and mild day. Models are in remarkably good agreement with this ridge for how far out it is in the forecast period, increasing confidence. Models however have the ridge flattening with an approaching broad trough, with significant differences in timing between the ECMWF (Saturday) and the GFS (Monday). Either scenario will bring rain back to the area with the flattening of this ridge. Snow levels generally hover around 4000 to 5000 feet, except for Wednesday and Friday when they go up to 6-8000 feet. Temperatures generally remain a little cooler than normal. -McCoy && .AVIATION...VFR conditions should generally hold at most taf sites until rain spreads eastward across the area between 12-18z Sunday. Coastal locations will likely drop into MVFR conditions for an extended period. Meanwhile, conditions should remain predominantly VFR inland, but cigs may lower enough around 21z Sunday that a few hours of MVFR conditions appears possible. PORTLAND AND APPROACHES...Rain associated with an incoming front will produce lowering cigs after 12z Sunday. East winds should keep conditions predominantly VFR, but as the winds turn southerly around ~21z Sunday, there may be a short period of MVFR cigs. /Neuman && .MARINE...An incoming front will bring strengthening south to southeasterly winds to the waters tonight. Winds should rise into Gale Force criteria of 35 to 40 kt across the outer waters Sunday morning. The stronger winds will take a while to develop across the inner waters. Given Gale Force winds struggled to develop near the coast in the last similar frontal storm system, confidence is a bit lower on whether or not they`ll actually develop this time around, but will nonetheless, keep the Gale Warning intact. Either way, seas should rise into the low to mid teens midday Sunday and Sunday afternoon before falling back below 10 ft Sunday night. Weak high pressure will slowly build across the waters Sunday night and Monday, which should result in less wind across the waters. However, an incoming westerly swell will likely push seas above 10 ft late Monday and/or Tuesday. In addition, another frontal storm system, albeit weaker than Sundays, will move into the waters Tuesday and/or Wednesday and bring gusty Small Craft Advisory level wind gusts of 25-30 kt. High pressure looks to then shift over the northeast Pacific and possibly bring us a brief period of summer-like northerly winds late next week./Neuman && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory from 9 AM Sunday to 4 PM PDT Monday for Cascades in Lane County-Northern Oregon Cascades. WA...Winter Weather Advisory from 9 AM Sunday to 4 PM PDT Monday for South Washington Cascades. PZ...Gale Warning from 11 AM to 4 PM PDT Sunday for Coastal Waters from Cape Shoalwater WA to Florence OR out 10 nm. Gale Warning from 6 AM to 3 PM PDT Sunday for Waters from Cape Shoalwater WA to Florence OR from 10 to 60 nm. Small Craft Advisory for Rough Columbia River Bar from 1 PM to 7 PM PDT Sunday. && $$ 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.