319 FXUS66 KPQR 302055 AFDPQR Area Forecast Discussion National Weather Service Portland OR 155 PM PDT Fri Jun 30 2023 .SYNOPSIS...Onshore flow is expected to continue over the next week with mainly dry weather and above average temperatures. Warm temperatures are expected through the weekend. However, a more substantial warming trend is likely early to mid next week, which could cause impacts around the upcoming holiday. There is potential for these very warm temperatures to persist through the end of the week. && .SHORT TERM...Friday night through Sunday night...Seasonably warm and dry conditions will continue through the weekend. Water vapor satellite imagery shows an upper level shortwave trough sliding across the Gulf of Alaska while upper level ridging over the Southwest US extends across the Great Basin. The shortwave trough will move east toward British Columbia tonight, clipping the Pacific Northwest, with more zonal flow aloft in its wake across the region on Saturday. High pressure begins to build over the NE Pacific into the Gulf of Alaska on Sunday as the upper trough slides into central Canada. At the surface, high pressure is expected to remain situated over the NE Pacific with low pressure east of the Cascades. Onshore flow will persist under this pattern with strengthening surface pressure gradients, leading to breezy north to northwest winds. Gusts up to 20-25 mph are possible in the late afternoon and evening hours each day for inland locations, and up to 30 mph along the coast. Breezy west winds are also expected through the central Columbia Gorge with gusts up to 30-40 mph. Above normal temperatures continue through the weekend with lowland highs generally in the mid to upper 80s. Probabilities of temperatures reaching or exceeding 90 degrees this weekend are now less than 10% across northern portions of the forecast area, and around 20-30% across the southern and central Willamette Valley. Along the coast, temperatures will remain more mild due to the onshore flow influence with temperatures in the mid 60s to low 70s. DH/HEC .LONG TERM...Monday through Friday...There is little change to the extended forecast as hot and dry weather will be the main impacts leading into the holiday week. WPC 500 mb cluster analysis indicates ensembles are in good agreement that on Monday the upper ridging over the NE Pacific will continue to build into the Gulf of Alaska, beginning to spread east to the PacNW coast and the lower heights will begin to shift into eastern Washington/Oregon. At the surface, high pressure will remain situated over the eastern Pacific with a thermal trough beginning to push north into Oregon. The warming trend is forecast to begin Monday with NBM deterministic guidance indicating high temperatures mainly in the low 90s across the lowlands. Probabilities of temperatures reaching or exceeding 90 degrees are around 50-70%. Tuesday and Wednesday are still slated to be the hottest days of the week. ECMWF Extreme Forecast Index (EFI) continues to suggest anomalously hot temperatures for these dates, as well as Thursday. WPC 500 mb clusters indicate the majority of ensemble members suggest heights continuing to build over the PacNW Tuesday into Wednesday, with only 20% of solutions indicating heights slightly lowering on Wednesday. At the surface, the thermal trough is expected to extend north over western Oregon. This will allow temperatures to rise to the mid to upper 90s across the lowlands. Even if the 20% of the ensemble solution occurs, temperatures would likely remain in the 90s. NBM probabilities of temperatures reaching or exceeding 90 degrees continues to remain high for the lowlands at 85-95% each day. Additionally, there is a 10-45% probability of temperatures reaching or exceeding 100 degrees. These temperatures will create a moderate risk of heat related illness, especially for those planning on spending extended time outdoors around the holiday. Thursday into late next week, ensemble guidance indicates the upper ridge will slowly retrograde west with heights beginning to lower over the PacNW. 500 mb cluster analysis shows there is some uncertainty on the timing of this as well as how much heights will lower. Because of this, temperatures could remain in the 90s Thursday and possibly longer with NBM probabilities of temperatures reaching or exceeding 90 degrees at 40-60%. NBM deterministic guidance has temperatures dropping to the upper 80s to low 90s for Thursday. This pattern is expected to create elevated fire weather concerns due to prolonged drying of fuels. Onshore flow is expected to continue through the forecast period with periods of breezy northwesterly winds with gusts up to 20-25 mph in the afternoon and evening hours. These winds could exacerbate fire weather concerns, especially with holiday activities, though the overall pattern does not suggest high fire weather concerns. Those spending time outdoors should practice heat safety as well as fire safety. -HEC && .AVIATION...Dry northerly flow across the region will maintain dry and mostly clear skies through Sat. The exception will be along the coast, where the offshore marine stratus will spread onshore again this evening, mainly to north of Lincoln City. May see areas of low stratus from Lincoln City to Florence later tonight, but these clouds likely only to extend bit inland, and not well into the river valleys. Either way, most of this stratus will follow trend of retreating back over the Pac by mid-late Sat morning. For detailed Pac NW aviation weather information, go online to: http://weather.gov/zse KPDX AND APPROACHES...Dry air mass with clear skies, and typical early summery diurnally driven winds. /Rockey && .MARINE...Not much change in the overall pattern, as high pressure remains anchored off the Pac NW coastline. Meanwhile, thermal low pressure will hug the south Oregon coast into northwest Calif. As such, will see tightening pressure gradients, with gusty afternoon/evening north winds on the waters. Will see bit of a letup of winds during the overnight hours, mainly close to shore. Gradients tighten a bit more on Saturday, enough to support 20 to 30 kt gusts on all waters by afternoon. Have extended Small Craft Advisory across all waters for Sat and Sat night. Interestingly, gusts of 30 to 35 kt not out of the question for areas to south of Newport later Sat afternoon into Sat evening. As such, will put up Gale Warning for those waters, with strongest winds expected to south of Yachats. Seas of 5 to 8 ft, with the higher, rather choppy seas to south of Newport. Winds will weaken slightly going into Sunday but expect advisory level northerly winds and periodically, steep wind driven seas through much of next week. /Rockey && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory until 8 AM PDT Sunday for Coastal waters from Cape Shoalwater WA to Cape Foulweather OR out 10 NM.Coastal waters from Cape Shoalwater WA to Cape Foulweather OR from 10 to 60 NM. Small Craft Advisory until 2 PM PDT Saturday for Coastal waters from Cape Foulweather to Florence OR out 10 NM-Waters from Cape Foulweather to Florence OR from 10 to 60 NM. Gale Warning from 2 PM to 11 PM PDT Saturday for Coastal waters from Cape Foulweather to Florence OR out 10 NM-Waters from Cape Foulweather to Florence OR from 10 to 60 NM. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland