Freezing fog? Here’s what it is, and why it’s sticking around the Tri-Cities all week
Tri-City residents woke up Monday morning to fog hanging over the Columbia Basin. But it wasn’t just regular fog that enveloped the Tri-Cities area.
It was freezing fog.
The National Weather Service in Pendleton, Ore. — the weather station that oversees the Tri-Cities area — issued a freezing fog advisory for the region on Monday morning that will last until at least 1 p.m. Tuesday.
“Roads will be slick where recent precipitation will refreeze on roadways, and freezing fog will add to the hazardous driving condition,” the advisory reads. “Primary impacts today are expected along the Columbia River where dense freezing fog remains. Freezing fog coverage is expected to expand overnight into Tuesday morning.”
Monday’s slippery conditions forced many school districts in the area and even some public agencies and businesses to delay opening their doors for a couple hours.
Freezing fog occurs when temperatures are between about 25 to 32 degrees. Miniature water droplets in the fog can instantly freeze on surfaces that are cold enough, including bridges, overpasses and cars.
“Fog at temperatures above freezing can be moist, but the moisture that comes out of the fog doesn’t freeze on things,” Joe Solomon, a meteorologist with the Weather Service in Pendleton, told the Tri-City Herald.
“When you have temperatures below freezing and fog, the moisture that comes out can freeze on objects,” Solomon continued. “Both of them have low visibility, but it’s the icing that can occur in the freezing fog.”
Temperatures below 25 can result in ice fog, Solomon said, which will result in fog freezing on trees and fences.
Temperatures in the Mid-Colombia region were expected to drop to 22 degrees Monday night, meaning ice fog could also be possible in the early hours Tuesday morning.
The Weather Service warned on Twitter that roads could flash freeze overnight due to the moist conditions and drop in temperature.
The Columbia Basin should see improved conditions throughout the day on Monday, with the worst fog occurring along the Columbia River, including the Tri-Cities area.
But clear skies will allow a surface-based inversion to move into the basin Monday night, Solomon said, resulting in another foggy night with low visibility and freezing fog into Tuesday.
“I expect it to maybe start to expand down the Columbia River Gorge up into the foothills of the Blue Mountains and probably starting to push west towards Yakima overnight,” Solomon said.
The Weather Service forecasts patchy fog every day through Friday this week, and temperatures will dip below freezing each day.
While a freezing fog advisory hasn’t been extended past Tuesday afternoon, further advisories may be issued throughout the week.
This story was originally published December 12, 2022 at 11:48 AM.
