015 FXUS66 KPQR 110318 AAA AFDPQR Area Forecast Discussion...UPDATED National Weather Service Portland OR 818 PM PDT Wed Oct 10 2018 Updated aviation section. .SYNOPSIS...Dry weather will persist through early next week with periods of offshore winds and mostly clear skies. Daytime temperatures will be above the normal, while nighttime temperatures remain normal or slightly below normal. && .SHORT TERM...Today through Saturday...An upper level ridge builds over the region tonight and Thursday and holds through at least Saturday. A surface thermal induced trough will develop over the coast this evening and shift offshore tonight as surface high pressure increases east of the Cascades. This will allow offshore flow to develop overnight. The east winds will be light tonight, but likely provide enough atmospheric mixing to inhibit radiation fog from developing. The dry east flow should also keep low marine clouds well off of the coast, and expect widespread mostly clear skies. Surface high pressure east of the Cascades weakens on Friday as an upper level shortwave trough moves into the Canadian Rockies. This will weaken the offshore winds across NW Oregon and SW Washington temporarily, and the surface winds may briefly turn onshore Friday afternoon. This change in winds will have little impact to the sensible weather and expect only slight changes in temperatures between Thursday and Friday. Some models suggest some marine clouds may spread down the WA coast Friday afternoon before the flow turns more offshore again Friday night. The thermal trough returns to the coast Friday night and increasing surface pressure east of the Cascades will strengthen the east surface pressure gradient across NW Oregon. East winds will gradually increase on Saturday. Subsidence will increase as the upper ridge moves inland, and daytime temperatures will warm above normal. ~TJ .LONG TERM...Saturday night through Wednesday...A 580+ mb upper level ridge holds over the Pacific NW through next Wednesday continuing dry weather with offshore winds and above normal daytime temperatures. A subsidence inversion will result in warmer overnight temperatures for the foothills and Cascades. Areas below the inversion will have radiation cooling and slightly cooler then normal nighttime temperatures. ~TJ && .AVIATION...Dry northerly flow aloft will maintain mostly clear skies through Thu. Though will see pockets of VFR clouds over the Cascades tonight, mainly over Washinton southward to Mt Jefferson. Other issue will be patchy fog or low stratus over the interior valleys, and possibly coastal valleys. Should not be as extensive as was Wed am, thanks to bit stronger offshore flow. KPDX AND APPROACHES...VFR tonight and Thu. At moment, think will not have any fog tonight or Thu, but may see patchy shallow fog along the Columbia slough between 10Z and 16Z. Rockey. && .MARINE...High pressure will build across the waters today and linger through early next week. This will result in a summer-like northerly wind pattern. Thermal low pressure will build over the southern Oregon coast later this week and will likely bring periods of gusty afternoon and evening winds to 25 kt to the central Oregon waters starting Friday. Seas continue to fall, currently sitting around 6 to 7 ft. Expect them to drop further to 4 to 6 ft tonight and stay there for the foreseeable future. May see very choppy to square seas with increased winds in the afternoons and evenings starting Friday, as wind wave will dominate. Bowen && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory for Rough Columbia River Bar until 8 PM PDT this evening. && $$ 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 CWA or forecast area.