Weekend Smoke Recap and A Look at the Week Ahead

Friday's Northern King County Smoke Event

Lake Forest Park air quality data from the Washington Department of Ecology.

Smoke levels spiked quickly in the several communities just north of Seattle Friday evening. PM2.5 concentrations at the Lake Forest Park air monitor peaked at 4:00PM, climbing briefly into the Very Unhealthy range, and prompting an Air Quality Alert as mentioned in the previous blog post.

GOES-18 visible satellite imagery. 9-5-2025 3:40 PM PDT

With several active fires in the state, you'd think it would be easy to find the culprit. Satellite imagery from late Friday afternoon shows both the Wildcat Fire and the Labor Mountain Fire burning actively. The Wildcat smoke plume, however, was still to the southeast of the impacted area as PM2.5 concentrations began to rise. 

In addition to the smoke plumes on satellite, a layer of smoke can be seen blanketing most of the state. Convective clouds can also be seen as mid-level moisture and instability moved northward into Washington. You can see some of these cloud features extending from western King County toward the Olympic Peninsula in the satellite image above.

GOES-18 visible satellite imagery. 9-5-2025 4:00 PM PDT

At this point in the day, these showers weren't very strong. At 4:00 PM, as concentrations were peaking at Lake Forest Park, you can see the band of clouds fizzling over far northwestern King County. The plume from the Wildcat Fire is still east of the impacted area.

As convective showers decay, they tend to produce downdrafts. A downdraft is a current of sinking air often associated with thunderstorms. This can be quite dramatic with a big thunderstorm on the plains, but they can also occur with weaker convective showers as well. It's hard to say with 100% certainty, but this is likely what occurred on Friday. As the clouds fizzled, a weak downdraft likely pushed some of the smoke toward the surface right into Lake Forest Park and surrounding communities. 

Eastern Washington Update

This prolonged period of poor air quality east of the Cascades continued through the weekend. Northeast Washington has been the hardest hit. Colville has reported UNHEALTHY FOR SENSITIVE GROUPS or worse since September 3rd. Several PurpleAirs along Lake Roosevelt and points south along the Columbia River have experienced periods of HAZARDOUS air quality due to active and, at times, extreme fire behavior on the Crown Creek, Katy Creek, Tacoma Creek, Snow Peak, and Lynx Mountain fires.

Further south along the Columbia, smoke from these fires in addition to the Rattlesnake Fire has brought the AQI to UNHEALTHY levels near the Grand Coulee Dam and even as far south as Soap Lake. 

On the east slopes of the Cascades, smoke from the Lower Sugarloaf Fire continued to impact Ardenvoir, Chelan, and Entiat, while smoke from the Wildcat Fire drained into the upper Naches Valley each morning.

The weekend also saw abundant lightning with more than 2,000 strikes in total across the state. Precipitation associated with these thunderstorms was very hit or miss, and new lightning ignitions have been discovered in the past 24 hours. Holdover ignitions will need to be monitored as the week progresses. With moderated fire weather conditions, smoke impacts from any new incidents are not expected to be widespread.

The Week Ahead

Air quality has improved over the weekend in western Washington, and that is expected to continue through the week with GOOD to MODERATE conditions expected. Fire activity at Bear Gulch has lowered with improved relative humidity and cooler temperatures, and monitors along Lake Cushman were also in the green Monday morning. Periods of elevated AQI can't be ruled out in the morning hours but expect more GOOD days this week.

East of the Cascades, air quality currently ranges from GOOD to VERY UNHEALTHY. The best air quality is generally found in south-central Washington and the Palouse. Heavier smoke remains in northeast Washington and in the previously mentioned impacted drainages. Because of this, Air Quality Alerts will remain in place in Chelan, Douglas, Ferry, Grant, Pend Oreille, Stevens, Yakima, and Benton counties.

Isolated to scattered thunderstorms are expected to continue along and east of the Cascades through at least mid-week. Once again, a mix of wet and dry storms are expected, and new ignitions are possible. Fortunately, cooler temperatures and improved relative humidity recovery should help initial attack on new incidents and reduce fire behavior on existing incidents. That said, with fuels as dry as they are, the fires already on the landscape will likely continue producing smoke impacts at a local level.