Weather experts explain freezing fog

Weather experts explain freezing fog

HUNTSVILLE, AL (WAFF) - Freezing fog across the Tennessee Valley made for a slow commute Tuesday morning and led to icy roads in some spots.

Many schools delayed their start times today as a precaution.

It created a nice winter scene to start the day across north Alabama. On trees, it looked pretty, but on roads, it created slick spots.

Andy Kula, senior meteorologist with the National Weather Service in Huntsville.
Andy Kula, senior meteorologist with the National Weather Service in Huntsville. (Source: WAFF)

Andy Kula, senior meteorologist with the National Weather Service in Huntsville, says in some areas, visibility was down below an eighth of a mile.

“Freezing fog is basically fog but when the temperatures are at or below 32 degrees, we call it freezing fog because the moisture in the air can freeze on contact. So that can be on trees, grass, cars and even roadways. Some areas had thicker coatings of frost than others,” he explained.

“Sometimes it can really look like a winter wonderland. Even if it didn't snow, it can look like it did and it's pretty fascinating,” he added.

Kula says freezing fog happens two or three times every winter.

“We get dense fog here all the time. But the traditional months for denser fog are the fall and spring months. If we do get dense dog, we have to worry in the winter because of the temperatures,” he said.

It causes concerns about visibility for motorists and deposits of frost on the roadways, leading to icy conditions.

“Plus, we had the rain that fell over the weekend and the rapid cooling Monday evening, which froze on some of the roads. The combination caused for hazardous travel Tuesday morning in some areas,” Kula said.

This time of year, it can take longer for fog to burn off. On Tuesday morning, it dissipated between 8-10am across the Tennessee Valley

During the summer months, it tends to dissipate quicker.

In Huntsville, especially in the valley areas, it was very thick, and it was widespread in the Shoals.

WAFF Meteorologist Eric Burke also weighed in on the unique weather event.

“Freezing fog is basically super cooled water, which is water that is below freezing but still in a liquid. When this super cooled water makes contact with something, whether it be sidewalk, roads or tree branches, you get freezing fogs,” he explained.

Along with poor visibility for drivers, he says it also causes ice to form on the roadways, especially on bridges and overpasses.

“Another thing you'll see in a freezing fog event is the rime ice that will stick to surfaces, like car windows, or tree branches, or even just sidewalks and hand railings,” he added.

(Source: WAFF)

Anytime fog is in the forecast, whether it's regular fog or freezing fog, Burke said, you need to allow extra time heading out the door and extra distance between you and the vehicle in front of you.

“Just plan on a generally slower commute. You might even have to warm up your car and with freezing fog, your car door may be frozen shut,” he stated.

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