The mid-Willamette Valley will remain in an air stagnation advisory until next Monday as dry weather continues throughout the region, according to the National Weather Service.
A temperature inversion, when a layer of cool air at the ground level is covered by a layer of warmer air, is trapping stagnant air in the area, said Andy Bryant, a hydrologist with the Weather Service office in Portland.
Since little wind and no precipitation is expected this week, air pollution, including smoke particles from outdoor burning, may become trapped at the ground level, Bryant said.
“It’s just kind of a matter of trying to reduce the rate at which things get worse, because it won’t get better until we see a significant weather pattern change,” Bryant said.
The Oregon Department of Environmental Quality is asking residents to refrain from outdoor burning and to use alternatives to wood stoves. Young children, pregnant women, people with asthma, those with lung or heart conditions and adults age 65 and older should limit vigorous outdoor activity, according to the DEQ.
“It’s going to be an increasingly unhealthy environment for those folks,” Bryant said.
Pollution levels tend to be highest during evening and morning hours, the DEQ said.
Bryant said there is a large area of area of high pressure over much of the western United States right now, creating temperature inversions in many valley locations that aren’t receiving much wind.
“Until we have a storm situation come in or some more wind to mix up the atmosphere, it’s not going to change,” he said.
No precipitation is expected through early next week, Bryant said.
The temperature inversion is causing cooler than normal temperatures in the mid-valley and is producing night and morning fog and low clouds, according to the Weather Service. High temperatures through the end of the week will be in the low 40s with overnight temperatures in the mid-20s.