Firefighters and residents on both sides of the Cascades should prepare for elevated fire weather conditions on Tuesday, September 22, as a trough of low pressure aloft drives breezy westerly winds through Cascade mountain passes and gaps while significantly drying out air masses across eastern Oregon and Washington.

What's Happening Today

According to the National Interagency Fire Center's September 21 situation report, a trough aloft will generate west winds gusting to 25 miles per hour through Cascade gaps during the afternoon hours. As these winds descend and warm on the lee (eastern) side of the mountains, relative humidity values are forecast to fall to 15–30 percent across eastern Oregon and eastern Washington.

These conditions — combined with cured grasses, dry forest litter, and low dead fuel moistures from a historically active fire season — create elevated risk for rapid fire spread if a new ignition occurs. Even fires that are highly contained can experience runs and spot fires under such conditions as gusty downslope winds can push embers beyond established containment lines.

Impact on Active Fires

Several active large fires in Oregon and Washington are positioned in terrain that makes them sensitive to Cascade wind events:

  • Hagen Fire (Umatilla NF, 89% contained): The fire's northern flank runs along terrain exposed to east-west wind corridors in the Blue Mountains east of Pendleton. Crews are on alert for any wind-driven runs.
  • King Fire (Okanogan-Wenatchee NF, 0% contained): Located just 7 miles northeast of Snoqualmie Pass on I-90, this 3,314-acre fire has no containment and sits in terrain directly affected by Cascade gap winds. Active fire spread is possible this afternoon.
  • Three Queens Fire (Okanogan-Wenatchee NF, 23% contained): At 9,566 acres just 6 miles east of Snoqualmie Pass, this fire is also highly exposed to today's wind event.
  • Ptarmigan Fire (Okanogan-Wenatchee NF, 73% contained): In Okanogan County near Mazama, afternoon winds could challenge firefighter progress on the uncontained portions of this 25,166-acre fire.

Outlook for the Week

Fire weather analysts note that conditions in the Great Basin and the Pacific Northwest are trending downward from the above-normal fire danger seen during peak summer. The weekly wildfire outlook for the week of September 21 shows the region stepping back toward normal as lighter winds and early-fall weather systems arrive. However, that transition period can be uneven, and individual wind events like today's can still produce fire weather watch or red flag warning conditions at the local level.

The National Weather Service's local forecast offices in Pendleton, Seattle, Spokane, and Boise are the authoritative sources for Red Flag Warnings and Fire Weather Watches in their respective zones. Residents and outdoor workers are encouraged to check NWS forecasts and county-level emergency alerts throughout the day.

Precautions for Residents

  • Avoid outdoor burning. Burn bans are in effect across many eastern Oregon and eastern Washington counties — check with your county or Oregon Department of Forestry for current restrictions.
  • Keep defensible space clear around homes. Even small fires can spread rapidly under 25 mph gusts.
  • Avoid parking vehicles in dry grass, as hot exhaust systems can ignite fires.
  • Report any new smoke or fire immediately by calling 911.

Conditions are expected to moderate somewhat Wednesday as the trough exits east and a more stable weather pattern returns to the region.