The inversion Thursday lifted during the day, but is expected return overnight and intensify over the weekend, according to the National Weather Service.
The Idaho Department of Environmental Quality initially issued a yellow air quality alert but later revised it to green, the lowest level on its scale and an indicator of good air quality.
The inversion Friday is expected to be at moderate levels, according to Elizabeth Padian, meteorologist for the National Weather Service.
“The lack of snow cover may have moderated the intensity of the inversion we see,” she said. “We're looking at staying in a bit of a pattern that will keep that inversion moderate.”
That means fog is predicted to dissipate before midday, but roll back in at night when temperatures go down, she said.
A system coming through over the weekend will hold the inversion in, Padian said.
“It looks like inversion conditions will return more strongly Sunday into Monday,” she said. “That looks like it will last early through next week.”
The high temperatures through the weekend are predicted to stay in the mid-30s. Thursday’s high could get up to 40 degrees. The lows are expected to be in the 20s and high teens, according to the National Weather Service.
The Treasure Valley won’t likely see much precipitation through the weekend, Padian said.
“Its looks like most of the rain and snow will stay to our south,” she said. But Bogus Basin could possibly see snow Thursday, with a 20 percent chance at precipitation, she said.