189 FXUS66 KPQR 090356 AAA AFDPQR Area Forecast Discussion National Weather Service Portland OR 856 PM PDT Tue Oct 8 2019 Updated Aviation and Marine discussions. .SYNOPSIS...An upper level trough over the region will bring scattered showers and cooler temperatures through early Wednesday. A ridge of high pressure will move into the region late Wednesday and persist through Friday for dry autumn weather. Another storm system is expected to move into the area this weekend. && .SHORT TERM...Tonight through Friday...A broad upper level trough of low pressure with scattered showers will continue to move across the region through early Wed. The attendant cold front moved through earlier today and brought about 0.3 to 0.5 inch of rain in the Coast Range and 0.3 to near 0.75 inch in the Cascades and foothills. The coldest air associated with the upper level trough remains well to our north in northern WA and southern BC. There have been a couple of lightning strikes in the Puget Sound this afternoon, but none in southwest WA as of 200 pm. The northern part of our forecast area in southwest WA remains marginally unstable, so will maintain a slight chance of thunderstorms in that area through early evening. As the cold air moves in later tonight, expect snow levels to drop to around 3000-3500 feet, but precip will be tapering so any snow accumulation will be light on the order of 1 to 3 inches. The upper level trough will move eastward into the northern Rockies on Wed with a ridge of high pressure building over the area in it's wake. As the trough moves eastward, thermal low pressure at the surface builds northward from northern CA in southwest WA with the flow turning offshore Wed afternoon/evening. Expect temperatures to be fairly chilly Thursday morning with low temperatures in the low to mid 30s throughout the valley. Some light frost is possible Thurs morning in outlying valleys The ridge of high pressure will dominate the weather pattern from late Wed through the end of the work week. This pattern will bring pleasant, dry autumn weather with daytime highs in the low 60s. Another storm system is expected to move into the region this weekend. /tw .LONG TERM...Friday night through Tuesday...The 12Z operational GFS and ECMWF models are in agreement for most of the long-term forecast. Both models show a cold front moving onto the coast Friday night. Precipitation from this front will dissipate slowly through Sunday night. Slight ridging will reduce precipitation on Monday but the next system closely follows with another front moving onshore late Tuesday. General temperature trend shows afternoon highs around 60 and over-night lows around 40. -BPhillips && .AVIATION...Showers associated with an upper trough and surface front will dissipate through 06Z Wednesday. Winds will continue to decrease, going near calm overnight. High pressure building in behind the front will clear skies overnight, which may allow some fog or low stratus to develop. However, expect light offshore flow to begin Wednesday morning, which should return conditions to VFR quickly, if not preclude flight restrictions completely. KPDX AND APPROACHES...There is a chance for some brief MVFR cloud development overnight, but confidence is low due to developing offshore flow. Bowen && .MARINE...Steep seas will continue overnight, fluctuating in the 9 to 11 ft range with dominant wave periods also 9 to 11 seconds. Extended the Small Craft Advisory for the waters off the central coast through 5 AM Wednesday, which now matches that for the waters off the northern coast. Winds will continue to weaken overnight and then become offshore around 10 to 15 kt Wednesday. Thursday through Saturday morning, seas will remain benign in the 4 to 7 ft range. Saturday afternoon, seas will begin to build as low pressure advances towards the West Coast. Bowen && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory until 5 AM PDT Wednesday for coastal waters from Cape Shoalwater WA to Cascade Head OR out 60 NM. Small Craft Advisory until 5 AM PDT Wednesday 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. This area is commonly referred to as the forecast area.