Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
840 FXUS66 KPQR 102250 AFDPQR Area Forecast Discussion National Weather Service Portland OR 250 PM PST Mon Nov 10 2025 .SYNOPSIS... A weak shortwave trough continues to pass through the region today, bringing scattered light showers and mid-level clouds across northwest Oregon and southwest Washington. Conditions will briefly dry out on Tuesday as high pressure builds. By Wednesday morning, the weather pattern turns cooler and wetter as a deeper system approaches from the northeast Pacific. Snow levels will fall Thursday into Friday, allowing for accumulating snow at Cascade passes. Unsettled weather is expected to continue through the weekend. && .SHORT TERM...Now through Wednesday...A weak front brushing the area is producing light precipitation mainly along the Cascade foothills this afternoon. Additional measurable rainfall through this evening remains possible, with the greatest likelihood across southwest Washington and the Cascades, while lower chances exist west of the mountains. Winds are light and variable this afternoon, generally around 5 mph from the south to southwest, shifting to northwesterly by evening. On Tuesday, a shortwave ridge builds in, producing some clearing and drier conditions in the morning. This temporary lull gives way late Tuesday night as a deep upper-level trough approaches from the northeast Pacific. A cold front associated with this system will cross the region on Wednesday afternoon, bringing widespread rain. The heaviest precipitation is expected along the coast and Coast Range, with more moderate totals in the interior valleys. Probabilistically for 1 inch or more of rainfall from 4 PM Wednesday to 4 PM Thursday, there is a 15-30% chance within the interior valley and a 50-70% along the Coast and Coast Range. Snow is also possible in the Cascades Wednesday into Thursday, though amounts remain uncertain. .LONG TERM...Thursday through Sunday...Snow levels are expected to fall Wednesday night into Thursday morning, though model guidance remains inconsistent, ranging from as high as 8,000 feet to as low as 3,500 feet. This uncertainty translates to low confidence in specific accumulation amounts. Current guidance suggests that between Wednesday afternoon and Thursday afternoon, there is a 30-50% probability that snow totals could reach 1 inch or more and a 10-20% probability that snow totals could reach six inches or more, clearly reflecting the uncertainty in snow levels and timing. Additionally, while the track of the low pressure system remains uncertain, it is possible to see gusty winds on Thursday. For chances of wind gusts above 35 mph on Thursday, there is a 15-30% chance inland and 30-50% chance along the coast. The coast could even see isolated wind gusts up to 45 mph as guidance suggests a 10-20% chance of such wind gusts to occur. The post-frontal air mass on Thursday will be cooler and slightly unstable, supporting isolated thunderstorm activity mainly along the coast, though overall chances have decreased as CAPE values are marginal. Any passing thunderstorms could produce lightning, heavy downpours, gusty outflow winds, and small hail. Temperatures aloft are trending slightly warmer than previous guidance, with 850 mb levels dropping to roughly 0-2C Thursday into Friday, which could place snow levels near Cascade passes, but with more uncertainty compared to previous guidance. From Thursday morning into Saturday morning, Santiam and Willamette Passes have a 40-60% chance of six inches or more of snow, while areas near Government Camp have slightly lower probabilities. A warm front lifting north on Saturday will raise snow levels above pass elevation, and wet conditions are expected to persist through the weekend as active weather continues. ~12 && .AVIATION...A front continues to slowly move through NW Oregon and SW Washington and is stretching from eastern Skamania County to around KONP as of 22z Mon. West of this line, inland terminals have improved to VFR whereas MVFR conditions for terminals south of the front, including KSLE and KEUG. These terminals may improve to VFR after the frontal passage after 23z Mon-01z Tue. However, VFR conditions are only expected to be brief as guidance indicates post-frontal stratus could develop in the Willamette Valley anywhere between 01-06z Tue with a 60-80% chance of MVFR ceilings. Guidance suggests conditions will return to VFR between 10-12z Tue in the northern Willamette Valley as winds become more northerly. Conditions could remain lowered or fluctuate between VFR and MVFR/IFR through 14-18z Tue for the central Willamette Valley, and will likely remain lowered through 19-22z in the southern Willamette Valley. Along the coast, MVFR conditions north of KTMK are expected to improve to VFR by 00-02z Tue. For KTMK and south, MVFR/IFR are expected to continue through around 02-06z Tue before improving. Variable winds less than 5 kts will turn northerly by 06z Tue. KPDX AND APPROACHES...VFR conditions are not expected to last long as MVFR/IFR ceilings could return again by 00-03z Tue. Easterly winds less than 5 kt today, turning more northwesterly after 00z Tue. -03 && .MARINE...Benign marine conditions continue through Tuesday night as weak high pressure builds over the waters. Winds will remain generally northerly with gusts less than 10 kts. High confidence (>95% chance) that seas remain below 10 ft at 10-12 seconds. The next low pressure system in the NE Pacific will return breezy southerly winds and building seas Wednesday into Thursday, with high confidence for another period of conditions hazardous to small craft. As this system swings a front through the waters, there`s a 60-80% chance of frequent southerly wind gusts exceeding 21 kt and a greater than 90% chance that seas build above 10 ft by Wednesday night. There is also a 40-60% chance for isolated gale- force wind gusts greater than 34 kt Wednesday- Thursday, with the highest chances across the outer waters beyond 20-30 NM. Active weather continues into the end of the week with additional systems moving through the waters. -10/03 && .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