Air pollution levels in Albany, Corvallis are listed as moderate

The dense fog that has blanketed much of the mid-Willamette Valley since the weekend is expected to remain until Wednesday morning.

The National Weather Service issued a dense-fog advisory for the valley stretching from Eugene to Portland this morning, and conditions are expected to be similar Tuesday. The advisory means that visibility is at a quarter mile or less.

According to the Department of Environmental Quality’s Air Quality Index, pollution levels in Albany and Corvallis are currently listed as moderate.

The heavy morning fog was the result of a temperature inversion and is typical for this time of year, according to meteorologist George Taylor of Applied Climate Services in Corvallis.

“It’s a cooler time of year and the sun doesn’t heat up the surface. The warmer air is above, causing an inversion and forming the clouds,” said Taylor.

He said a lack of wind contributes to the problem.

Taylor also said that December is usually the foggiest month of the year in the Northwest, thus more dense fog is likely before the end of the year.

Today’s fog lifted by late morning in Albany and by early afternoon in other areas, giving way to sun breaks. Patchy fog is expected tonight and through Tuesday morning, again giving way to sun breaks in the afternoon.

Wednesday, fog is expected to lift earlier in the day, with the possibility of rain moving in by late afternoon. After that, showery conditions are predicted through Sunday.

The weather service said high temperatures should remain in the low to mid 50s and high 40s through the weekend.