Weathercatch: Freezing Fog is here – it’s lovely but creepy

Perhaps you’ve heard of the fog bowl. No, not the iconic 1988 NFL game when dense fog rolled over Chicago’s Soldier Field, blocking spectators from seeing the Bears beat the Eagles. The fog bowl we’re talking about is where we happen to live.

Look no further than recent days to see why, this time of year, Eastern Washington is often referred to as the fog bowl. After a high pressure system stalled overhead the first week of December, our region experienced patches of plain fog and the freezing variety every day for more than a week.

Foggy air over the state’s eastern half during winter is fairly common. But as we just saw, our region is vulnerable to freezing fog as well.

We reside in the Columbia Basin – bordered by Cascade Range to the west, the Okanogan Highlands to the north, the Coeur d’ Alene range to the east and Blue Mountains to the south. The result is a topographical bowl that traps cold air and fog. Add below-freezing temperatures to the mix and it can become a downright menace: freezing fog.

The stubborn ridge of high pressure parked over the Pacific Northwest helped lock in clear, calm skies and cold temperatures in our bowl. This, combined with chilly moist air near the ground, produced fog so hazardous at times that the National Weather Service urged motorists to use caution. Not only did pockets of dense fog shroud roadways, but it froze to their surfaces and caused dangerously slippery driving conditions.

Fog is basically a cloud that forms at ground level. Freezing fog develops when temperatures near ground level are at or below freezing. As fog droplets come into contact with a solid surface, they instantly freeze into a layer of ice.

Social media has been loaded with photographs depicting the beauty of frozen fog wafting over hills, along with tiny white crystals affixed to fence posts, grass blades and tree branches. But when affixed to stairs, sidewalks and roadways, it’s a much different story.

Freezing fog creates a slippery surface that can be hard to detect. First, there’s no falling precipitation such as snow or freezing rain to alert us of a potential hazard. Also, freezing fog creates a thin ice layer that’s often transparent on pavement. Consequently, we have no way to identify ice until our tires suddenly slide or our feet slip.

Keep in mind that bridges, overpasses and spots on the road shaded by trees and other structures are especially prone to ice patches deposited by freezing fog. Because these paved areas are exposed to more cold air, they freeze before other surfaces. Take, for example, a 23-car pileup that occurred almost a year ago on the Umatilla Bridge south of Kennewick. During the early morning of Dec. 16, 2019, unsuspecting motorists slid out of control after hitting black ice left by a pocket of drifting freezing fog. The chain reaction crash closed the bridge that connects Washington and Oregon along Interstate 82 for five hours as people were treated at the scene or taken to the hospital.

So while freezing fog adds lovely poetry to our landscapes, keep in mind it may well be the most dangerous weather hazard on the road. To reduce the risk of being in an accident, we hope you’ll drive slower than usual, use headlights and maintain safe following distances. The website drive-safely.net/driving-in-fog/ offers more useful information for driving in fog.

Be safe.

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Nic Loyd is a meteorologist in Washington state. Linda Weiford is a writer in Moscow, Idaho, who’s also a weather geek. Contact: ldweiford@gmail.com