Portland wildfire smoke forecast
The map above shows NOAA HRRR-Smoke near-surface PM2.5 for the next 48 hours, updated hourly, with active fires from NIFC and live AQI from EPA AirNow monitors. It opens over Portland.
Portland sits at the north end of the Willamette Valley near 50 feet of elevation, boxed in by the Coast Range to the west and the Cascades to the east. The Columbia River Gorge is the one real gap in that wall, and it is the single most important piece of terrain in any Portland smoke forecast.
Where the smoke comes from
Cascade fires are the danger, and east wind through the Gorge is the delivery mechanism. A fire on the west slope of Mount Hood or in the Santiam or Clackamas drainages can sit harmlessly upwind for days, then be funnelled straight into the metro area when the pressure gradient turns easterly. Southern Oregon and northern California fires contribute a slower, higher-altitude haze on top of that.
How long it lasts
The Gorge east wind is usually broken by returning onshore flow off the Pacific, which arrives through the same Coast Range gaps that bring the marine layer. Once westerly flow is established the valley flushes quickly. The valley also pools smoke overnight on its own, so mornings routinely read worse than the previous afternoon even with no new smoke arriving.
Past smoke events
September 2020 is the reference event. East wind drove the Riverside, Beachie Creek, and Lionshead fires toward the valley and gave Portland some of the highest PM2.5 concentrations ever recorded in a major American city, lasting more than a week.
Running, riding, and trailheads
Forest Park and the Gorge trails are the first things people give up, and the Gorge is a bad choice during an east-wind episode specifically because it is the corridor the smoke is travelling through. Mount Hood trailheads on the south side sometimes sit above the valley layer while Portland does not.
Reading the map
Use the layer toggle to compare NOAA HRRR-Smoke with the ECCC FireWork model. When the two disagree, treat the higher reading as the cautious call.
Near-surface is the product that maps to what you breathe and to AQI, not the high-altitude column that only tints the sunset. A sky that looks bad and a monitor that reads fine are usually both correct, and they are describing different layers of air.