Area Forecast Discussion
Issued by NWS Portland, OR

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000 FXUS66 KPQR 032120 AFDPQR Area Forecast Discussion National Weather Service Portland OR 220 PM PDT Mon Aug 3 2020 .SYNOPSIS..A mixture of morning clouds and afternoon sunshine with temperatures near to slightly above average for the next several days. Widespread light rain is expected to start late Wednesday night and persist through Thursday. Friday look for breezy conditions with temperatures close to average. && .SHORT TERM...Tonight through Wednesday...The morning marine clouds along the coast will continue to recede into the evening hours as shortwave ridging will build through tonight. This pattern will maintain rather clear skies inland but, expect the coast to maintain some clouds as moist onshore flow will persist. On Tuesday, expect breezy conditions across the CWA as a thermally induced trough briefly develops within the Willamette Valley, along with gusty conditions within the central and eastern part of the Columbia River Gorge and gaps along the Cascades. /42 .LONG TERM...Wednesday night through Monday...Models and ensembles continue to remain in overall agreement that the next system will start to slide southeast along the British-Columbia Coast starting Wednesday night. This distended trough will extend down towards the CWA and looks to provide a fair chance for rain starting Thursday. There is remains a fair amount of uncertainty between the model families as to the exact timing and amount of the precipitation but, they all do agree that there is a chance for precipitation on Thursday across the CWA. Friday and into the weekend the forecast becomes a lot less cohesive as model families start to diverge significantly in the overall pattern. GEFS models have shortwave troughing developing Friday and persisting through Monday. While EPS models have shortwave ridging developing for the weekend and becoming more zonal by the start of next week. CMCE models develop a zonal pattern for the weekend followed by a shortwave trough for the start of next week. Taking all of this into account have chosen to go with a blend of models which has very little change if any from the NBM . Overall, what can be expected is onshore flow to persist from Friday through Monday along with closer to seasonal temperatures for the CWA. /42 && .AVIATION...Mainly VFR across the area early this afternoon. The exception continues to be along the coast, where areas of MVFR exist. These MVFR areas are likely to become more localized through the afternoon. IFR to MVFR stratus returns to the coast between 03Z and 06Z Tue, with the possibility of LIFR overnight. Expect coastal conditions to gradually lift Tue morning and become VFR by 19Z. VFR will be rule inland through at least 07Z Tue. Guidance suggests areas of MVFR stratus may push into the far western Oregon Coast Range valleys overnight, as well as the southwest Washington coastal lowlands. IFR to low-end MVFR stratus dissipates by 19Z. KPDX and APPROACHES...VFR at the terminal and vicinity through at least 12Z Tue. Latest high-resolution model cloud guidance indicates MVFR stratus developing along the Columbia River from near KSPB to KTTD around 13Z Tue and will dissipate by 19Z. Weishaar && .MARINE...Surface high pressure over the waters will be the dominant feature through Wed. Thermally-induced surface low pressure builds over the far south Oregon coast Wed afternoon, which will enhance the prevailing northerlies. The 12Z model guidance indicates 20-25 kt boundary layer wind speeds generally south of Cascade Head late Tue afternoon through Tue evening. At this time, will hold off on issuing an advisory. Gradients weaken Wed as a frontal system approaches the waters. Guidance indicates a narrow ribbon of 20-25 kt northwest wind gusts 12Z Thu behind the front, but looks to be short-lived. Typical summertime northerlies return Fri into the weekend for a much higher likelihood of small craft advisory level wind. Seas are currently around 3-5 ft and will remain in this range through Wednesday. Seas look to then build to around 5-7 ft by Thursday then to around 6-8 ft later this week. Longer range guidance shows sub-10 ft seas Friday through the weekend. Weishaar && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland

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