Smoky air that blew into Inland Northwest in a few hours Thursday afternoon likely will persist through at least Saturday as a 12-day heat wave gives way to moderating temperatures, but also gusty winds.
The blue-brown haze from Central Washington wildfire smoke sent air quality in Spokane from the good range Thursday morning to the unhealthy level by 4:30 p.m.
The government’s air quality index peaked at a reading of 154, just above the threshold of 150 for air pollution that is considered unhealthy for the general population.
Similar readings were reported east of Spokane in North Idaho.
Forecasters said that fine particles from smoke can be a health hazard. They recommended reducing outdoor activities or staying indoors. Burning eyes, runny nose and scratchy throat are typical symptoms caused by smoke. Lung conditions can be aggravated.
A “red flag” alert for high fire danger from wind and low humidity was extended through 11 p.m. today with more winds in the forecast.
Gusts to 38 mph as measured at Wenatchee on Thursday prevented smoke plumes from rising into the sky. Instead, low-level winds spread the smoke eastward along the ground. Spokane reported gusts to 25 mph.
“It got bad real fast,” said Lisa Woodard, a spokeswoman for the Spokane Regional Clean Air Agency.
She said the last time air quality approached Thursday’s level was during another outbreak of wildfires in central Washington in September 2012. The air quality index is on a scale of 1 to 500 with readings above 300 in the worst category, hazardous.
The smoke problem prompted the National Weather Service to post air quality alerts for the region, including North Idaho.
At least four major fires were burning across north central Washington, including the lightning-caused Chiwaukum Creek Fire west of Leavenworth, first detected on Tuesday after Monday thunderstorms.
That fire forced closure of U.S. Highway 2 between Leavenworth and Cole’s Corner on Thursday.
Residents of 860 homes have been told they should leave immediately, fire officials said. Another 800 homes were less seriously threatened. Light ash fell in Leavenworth, according to the Associated Press.
A group of lightning-caused fires, known as the Carlton Complex, had burned 4,400 acres near Winthrop, according to the Northwest Interagency Coordination Center. That fire started Monday.
The other big blazes are the Mills Canyon Fire near Entiat, which started July 8 and has burned 22,500 acres, and the R Road Fire near Mansfield, which started Wednesday and had burned 4,250 acres.
Numerous smaller blazes were reported across the region, including in Kittitas and Yakima counties.
With the warm temperatures and gusty winds, Spokane County, the city of Spokane and Spokane Valley issued burn bans for most recreational fires. The bans apply to the cities of Liberty Lake and Millwood.
Under them, no outdoor recreational fires are allowed. Residents still can use backyard barbecues. Portable outdoor fireplaces are allowed if the device has a spark arrester and approved fuels such as seasoned firewood, propane or briquettes are used.
Until Thursday, smoke had stayed elevated in the atmosphere as a result of the hot weather pattern, which was favorable to rising smoke plumes.
Weather forecasters said the heat wave allowed a thermal low pressure area to build along the east side the Cascades, letting smoke rise vertically into the middle atmosphere, keeping it well above the ground through Wednesday. That weather feature has moved to the east as a weak cold front ushered in the winds and moderating temperatures on Thursday.
Smoky skies overhead created an eerie orange glow in Spokane on Thursday morning. From noon to 1 p.m., the visible smoke along the ground increased dramatically.
Winds through the weekend will be strengthened by cool Pacific marine air moving into the passes and gaps in the Cascades and spilling downward along the east slopes and across the Columbia Basin.
Ellie Kelch, a weather service forecaster in Spokane, said the smoke “is going to roll downhill into the basin.”
Overnight temperature inversions were expected to intensify smoke concentrations at dawn through Saturday and possibly Sunday. Highs should go from the upper 80s today to lower 80s on Sunday in Spokane.
Gusty winds are expected to return during the day through Saturday, initially clearing some of the smoke, only to be replaced by a new shot from the wildfires, Kelch said. Gusts to 30 mph are possible Saturday in Spokane.
Woodard said that clean air agency scientists hope moderating temperatures in the Cascades will reduce the volume of fire and smoke from Thursday’s levels.
The counties affected by the air quality alert are Spokane, Chelan, Okanogan, Douglas, Grant, Adams, Lincoln, Garfield, Asotin, Whitman, Ferry, Stevens and Pend Oreille in Washington and all of North Idaho as far south as Nez Perce and Lewis counties.
A check of emergency rooms at Providence Sacred Heart Medical Center and Providence Holy Family Hospital showed no patients with lung problems, but a doctor reported that as time goes on with poor air quality, patients with lung conditions may start appearing for treatment, a Providence spokeswoman said.