891 FXUS66 KPQR 250439 AAA AFDPQR Area Forecast Discussion...UPDATED National Weather Service Portland OR 938 PM PDT Thu Jul 24 2025 ...Updated aviation discussion... .SYNOPSIS...A cool down back to near normal is expected Friday through Sunday as a large trough dips south into the PacNW. Expect upper 70s to low 80s. Another warm up is expected early to mid next week. && .DISCUSSION...Satellite imagery shows mostly clear skies across the region with very sparse fair weather cumulus beginning to pop up. The upper level pattern is a bit messy with a large trough across western Canada and eastern Alaska and a cut-off low over central California. In between these two features, an elongated area of high pressure covers a good portion of the northern Pacific from Oregon to the Aleutian Islands. This will support highs topping out in the mid 80s inland and upper 60s along the coast. Expect another solid marine layer to push into the coastal areas late this evening into the overnight. HREF guidance is suggesting another decent chance (40-70%) that stratus will develop along the Cascade foothills and backbuild into the Willamette Valley between 3-6 AM Friday. Any clouds that develop inland are expected to dissipate by late Friday morning. Expect a modest cooldown from Friday into the weekend as the region increasingly feels the influence of the upper level trough to the north, bringing lowering 500 mb heights and maintaining benign onshore flow west of the Cascades. This will equate to inland highs closer to seasonal norms in the upper 70s to low 80s through Sunday. Coastal areas will continue to be impacted by abundant marine stratus through the period, with diurnal intrusions into the inland valleys becoming increasing likely as the marine layer deepens and onshore pressure gradients increase. Guidance continues to suggest temperatures rebound back into the upper 80s to low 90s Monday through Wednesday. Probabilities for inland valleys to reach 90 degrees on Monday are modest at 10-40% but increase significantly Tuesday and Wednesday to 50-80% for most locations. A significant heat event is unlikely at this time given the relatively small temperature spread heading into next week. A deepening upper level low is also likely to set up off the British Columbia coast, through there is a wide area where this may set up. Depending on where it sets up, south to southeast flow could set up across the are or at least a portion of the area, bringing monsoonal moisture and potential for thunderstorms. Thunderstorm probability remains below 15% for now and does not warrant inclusion in the forecast at this time, but will have to continue to monitor going forward depending on the ultimate position and orientation of the trough. -Batz/CB && .AVIATION...Satellite imagery as of late Thursday evening depicts marine stratus along the coast bringing IFR/MVFR conditions to KAST and KONP. High confidence that these conditions prevail along the coast through Friday morning. Marine stratus should break out and return VFR conditions to the coast by 21-23z Fri, but there is some guidance that suggests stratus could linger throughout the day. Will also see a stronger onshore push tonight, bringing a 60-80% chance that MVFR stratus moves into the Willamette Valley between 12-18z Fri (highest chances across the Portland/Vancouver Metro Area). VFR conditions with mostly sunny skies return to Valley terminals by 18-20z Fri. Expect generally northerly to northwesterly winds across the region around 5-10 kt, strongest in the afternoon. PDX AND APPROACHES...High confidence (70-90% chance) for MVFR CIGs across the Portland/Vancouver Metro between 13-18z Fri. Stratus should begin clearing out as daytime heating progresses, returning VFR conditions by 18-19z Fri. Northwesterly winds 5-10 kt. -Alviz && .MARINE...Going through the end of the work week through the weekend high pressure will maintain north to northwesterly winds with gusts around 13-18 knots during the afternoon/evening hours each day. Background swells don`t look particularly noteworthy so seas likely remain around 3-6 ft each day into next week - small Craft advisory conditions are unlikely this week. That said, it`s worth pointing out there will be some strong ebb currents through the Columbia River bar late this week (Friday morning) which may lead to locally choppy seas. -Schuldt && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland