Worsening freezing fog will create icy threat this weekend

By Linda Weiford, WSU News

PULLMAN, Wash. – The freezing fog that’s been coming and going this week in the eastern half of Washington state is expected to intensify, causing slick roads and decreased visibility throughout the weekend.

Foggy class change on WSU campus
Fog covering the WSU campus one recent afternoon. (Photo by Dean Hare, WSU Photo Services)

The fresh bout of freezing fog — likely to form in pockets tonight and become more widespread Saturday through Monday morning – has the potential to create hazardous icy spots on roadways and sidewalks, according to meteorologist Nic Loyd of Washington State University’s AgWeatherNet.

“People will want to take their time going places. Not only could the fog make it hard to see, but it could produce black ice, making driving and even walking deceptively slippery,” he said.

The freezing fog forecast is the result of a high pressure system that’s bringing cooler temperatures and calm air into much of the Pacific Northwest. A temperature inversion, when the cold air is trapped by the warm air above it, will hang around for a few days and keep the fog from dissipating while also trapping pollutants.

The combination of stagnant air and plenty of ground moisture will help create the fog while below-freezing air temperatures will make water droplets in the fog freeze, said Loyd.

“When the temperature drops below freezing, those water droplets can rapidly freeze on roadways and other surfaces. Unlike snow, the resulting ice layer may not obvious to motorists or pedestrians because it’s transparent,” he said.


Media contacts:

Nic Loyd, WSU meteorologist, 509-786-9357, Nicholas.loyd@wsu.edu

Linda Weiford, WSU News, 509-335-7209, linda.weiford@wsu.edu