Area Forecast Discussion
Issued by NWS Portland, OR

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000 FXUS66 KPQR 222159 AFDPQR Area Forecast Discussion National Weather Service Portland OR 252 PM PDT Sun Jul 22 2018 .SYNOPSIS...High pressure continues to build over the region today, ushering in several days of very warm temperatures across the interior portions of the forecast area. Meanwhile, a thermally induced surface trough builds develops over the Willamette Valley. Inland afternoon temperatures will remain in the 90s through the week as the strong upper level ridge persists, though a disturbance moving north of the area may provide some increasing clouds late in the week. && .SHORT TERM...Tonight through Wednesday night. Clear skies across most of the forecast area this afternoon with a few exceptions. Marine stratus has remained along over the coastline, and will continue to occasionally move onshore around Newport. Elsewhere, some relatively thin high clouds are moving north into the eastern half of Lane County; however, these should be thin enough to have little if any impact on temperatures. Some light smoke in the atmosphere also is drifting north into Lane County from fires in southwestern Oregon per latest satellite imagery. Will continue a mention of this in the forecast for the Lane County Cascades and foothills for the next day or so, given current trends. Very little change made to the temperature forecast for the next two days. The forecast remains on the high end of guidance, but seems reasonable given the warming of the air mass under the building upper ridge, the placement of the thermal trough, and recent model performance (i.e. a cool bias during the last stretch of heat earlier this month). This means that we`ll see temperatures in the mid to perhaps upper 90s for Monday and Tuesday, so the Heat Advisory for the interior lowlands on these days will remain unchanged at this time. Expect that evening cooling will be slow to occur given the very hot daytime temperatures, so overnight relief may be hard to come by, especially in the urban centers and in the Portland metro area and for those who don`t have access to air conditioning. Models suggest that the thermal trough shifts slightly east on Tuesday for slightly cooler, but still hot inland temperatures Tuesday afternoon. Wednesday ultimately looks like another rather warm day across the interior with high temperatures in the lower to mid 90s. Depending on the evolution of the next few days, the Heat Advisory may need to be extended another day for at least some of the forecast area. Meanwhile, the forecast for the coastal areas will be on the mild side (generally 3-5 degrees above normal), but the influence of the sea breeze will serve to keep temperatures from getting too hot each day. Coastal low temperatures will also recover to near normal each night, so significant impacts from heat are not anticipated for the coast. Cullen .LONG TERM...Wednesday night through Sunday. An upper level trough advances into southern British Columbia or northwestern Washington late Wednesday into Thursday, briefly lowering heights and likely increasing the depth of the marine layer a little bit. However, the marine influence across the interior is likely somewhat limited, so afternoon temperatures are expected to hold in the lower 90s Thursday and Friday. Forecast models suggest the strong ridge over the Great Basin will again amplify late Saturday and Sunday, which could again drive temperatures across the interior well into the mid or upper 90s. Have keep the forecast towards the middle of the envelope of guidance at this time due to the lower confidence in the details of the pattern evolution, but the temperature forecast for next weekend may need to be adjusted warmer if the current model trends hold. Cullen && .AVIATION...High pressure across the forecast area will result in predominately VFR conditions under mostly clear skies the next 24 hours. The exception will continue to be along the coast where marine stratus could bring periods of reduced flight conditions this afternoon. Widespread IFR fog/stratus appears likely along the coast after sunset and will likely continue through late Mon morning. Otherwise, conditions remain mostly VFR. Smoke from wildfires over southern Oregon is starting to drift north this morning and may impact the south Willamette Valley today. Expect smoke layer to remain above 10,000 ft AGL. KPDX AND APPROACHES...VFR under clear skies the next 24 hours. /64 && .MARINE...High pressure over the northeast Pacific and thermal low pressure over southwest Oregon will result in a fairly typical summer-time northerly wind pattern for the upcoming week. Winds will continue to flirt with advisory criteria during the afternoon and evening hours through the week, with occasional gusts to 25 kt possible, but do not think they will be frequent or widespread enough to justify an advisory. Seas will be around 4 to 6 ft through the week and could become choppy at times, but will likely remain below advisory criteria too. /64 && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Heat Advisory from 2 PM Monday to 11 PM PDT Tuesday for Central Columbia River Gorge-Central Willamette Valley-Greater Portland Metro Area-Lower Columbia-South Willamette Valley- Upper Hood River Valley-Western Columbia River Gorge. WA...Heat Advisory from 2 PM Monday to 11 PM PDT Tuesday for Central Columbia River Gorge-Greater Vancouver Area-I-5 Corridor in Cowlitz County-Western Columbia River Gorge. 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 CWA or forecast area.

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