Smoke cloud darkens Spokane sky

Treacherous weather on raging wildfires in Okanogan County sent an elevated plume of smoke over the Spokane area this evening while air quality at ground level deteriorated to the unhealthy category for persons with health issues. The cloud darkened the sky and turned the sun orange, sending an eerie orange-brown light over the city. Earlier in the day, the pollution level from wildfire smoke was in the moderate range in Spokane. Ron Miller, forecaster with the National Weather Service in Spokane, said that fire weather conditions deteriorated badly today, allowing fires to grow and spread rapidly. The North Star fire in north-central Okanogan County was primarily responsible for this evening’s smoke cloud, which was clearly visible on satellite images. At the same time, smoke at ground level was coming from the Carpenter fire near Fruitland in Stevens County. Air quality in Spokane was improved during much of the day, but the forecast is calling for a return to unhealthy air on Thursday. Other locales in the Inland Northwest were seeing much worse air pollution from smoke, according to AirNow, a website that tracks air quality around the country. The worst areas were closest to the fires this afternoon, according to the AirNow map. Miller said that a thermal low-pressure area made it easier for fires to grow by allowing more lift vertically. In addition, the upward lift also led to variable winds. Dangerous fire weather under a thermal low can be very unpredictable since updrafts and downdrafts cannot be anticipated easily, he said. That is different than a situation like last Friday when the danger from horizontal winds was readily apparent. Satellite images also showed evidence of unusual pyro-cumulus clouds that were caused by extreme upward lift above the fires into colder air, which caused water vapor to condense, Miller said. A red-flag warning for dangerous fire weather is in effect through Friday. A cold front is expected to increase winds on Thursday and continuing Friday with steady winds of 20 to 30 mph with gusts to 40 mph in some areas. In Spokane, gusts may reach 25 mph out of the southwest Thursday and then 30 mph from the west on Friday. Fire zones northwest of Spokane are expected to see northwest winds.