SEATTLE — The National Weather Service has issued a Freezing Fog Advisory for the second day in a row after freezing fog impacted travel in parts of western Washington Tuesday morning.
So, what is freezing fog and how can it affect people and travel?
What is freezing fog?
Freezing fog occurs when supercooled water droplets in fog can freeze on exposed surfaces when temperatures are at or below freezing, according to the National Weather Service.
On Tuesday morning, temperatures dipped into the 20s across western Washington. Some of the coldest spots were Bremerton and Puyallup, which dropped to 23 degrees overnight.
The fog can freeze on tree branches, stairs, sidewalks, roads and cars. If it freezes on roadways, black ice can form, which is especially difficult to see. The road may look normal or even a little wet when there are patches of black ice on top.
How is fog affecting western Washington?
Seattle-Tacoma International Airport had implemented a ground stop for about three hours Tuesday morning for arriving traffic due to fog. Departure delays were between 15 and 30 minutes and increasing due to weather. The ground stop lifted around 11:15 a.m.
The Washington State Department of Transportation said it treated roadways, as highways were expected to be slick Tuesday morning.
A crash on Interstate 5 also complicated travel Tuesday morning, causing a 10-mile back-up near Kent and state Route 516.
The National Weather Service urges people to slow down on the roads, use headlights and leave plenty of distance ahead of them. People should be alert for frost on bridge decks, which causes slippery roads.
Freezing Fog Advisory
The Freezing Fog Advisory is in effect until noon on Wednesday for Seattle, Tacoma, Olympia, Lacey, Tumwater, the southwest interior, the Hood Canal area, and Bellingham.