Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
588 FXUS66 KPQR 171742 AFDPQR Area Forecast Discussion National Weather Service Portland OR 1042 AM PDT Mon Aug 17 2026 Updated aviation discussion. && .SYNOPSIS...Seasonably warm and dry conditions expected through much of the week with morning clouds and afternoon clearing. Winds generally out of the west to northwest, strongest in the afternoon and along the Central Columbia River Gorge and Upper Hood River Valley. Next chances for light showers arrive Friday into next weekend. && .DISCUSSION...Now through Saturday...Minimal changes to the forecast. Seasonably dry and warm conditions continue through the week with minimal weather impacts. The large-scale pattern remains stagnant through the period, with broad and relatively flat upper-level ridging over the majority of CONUS and a weak, positively-tilted upper-level troughing over the northeast Pacific. This pattern will support continued onshore flow, maintaining near-normal daily high temperatures in the 80s within inland valleys and 60s along the coast, and overnight lows in the 50s across the region. Mornings will be characterized by clouds, especially along the coast, which will tend to clear by the afternoon. Light west to northwest winds will, peaking each afternoon. The strongest winds are likely to be along the Central Columbia River Gorge and Hood River Valley, but impacts are not anticipated. The majority of ensemble members are in agreement that upper- level ridging over the Rockies and Great Basin will build late in the workweek, which would favor a brief warm-up on Thursday. However, ensemble guidance continues to show the upper-level trough over the northeast Pacific shifting onshore Friday into the weekend, resulting in slightly cooler temperatures and winds coming from the south/southwest. Chances for showers also increase to 10-25% across the region during this time, with the highest chances over the Coast Range and Cascades. However, there is still high uncertainty in the timing and potential rain amounts. A weak front at the end of the week would have a hard time counteracting the dry airmass in place, making accumulating rainfall unlikely and keeping most places dry. -10/36 && .AVIATION...Through 18z Tuesday...At 1730z Monday, marine stratus remains along the coast and portions of the interior lowlands in NW OR and SW WA, though satellite imagery shows that it is slowly dissipating. Stratus is expected to completely dissipate by 19-21z as daytime heating progresses, returning VFR conditions with high clouds across all terminals. Marine stratus quickly builds again along the coast after 00-03z Tue, returning IFR/MVFR CIGs (>80% chance). There`s a 20-40% chance of MVFR stratus pushing east along the Columbia River and forming in the northern Willamette Valley after 12z Tue, including KPDX, KTTD, and KUAO. There`s a 10-25% chance of MVFR cigs forming at KSLE and KEUG, as well. Any MVFR conditions at inland terminals should improve to VFR by 18-20z Tue. Northerly to northwesterly winds today 10-15 kt with gusts up to 20 kt along the coast, and 5-10 kt across the Valley. Winds will be strongest in the afternoon and evening, then weaken overnight. KPDX AND APPROACHES...Low-end MVFR (1-2 kft) CIGs continue and should dissipate and return to VFR conditions with high clouds by 19-21z Mon. There`s a 25-40% chance of MVFR CIGS returning after 12z Tue. Northwesterly winds 3-7 kt, strongest in the afternoon and evening, decreasing overnight. -03 && .MARINE...A largely stagnant pattern continues through much of the week with high pressure offshore supporting northerly to northwesterly winds of 8-15 kt and afternoon gusts up to 20 kt. Weak low pressure moving over the northeast Pacific Friday into the weekend will shift winds out of the south to southwest across the waters, but chances for gusts exceeding 21 kt remain low, only 5-10%. Seas of 3-6 ft persist through the period. Increasing periods of 12-14 sec on Tuesday-Wednesday may result in a moderate risk for sneaker waves along the coast. Caution should be used when in or near the water. -10/36 && .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