This morning's key phrase: freezing fog.  But what is freezing fog?

To put it simply, it's when there is fog during freezing temperatures and when the moisture comes in contact with cold surfaces, it freezes.

This caused many roads and elevated roadways to develop black ice this morning leading to the closure of an on-ramp from La. 3132 to I-49, as well as causing major issues on Cross Lake Bridge on I-220.

"Fog develops when the dew point drops and matches the actual air temperature," AccuWeather meteorologist Maggie Johnson explained. "When you get the right setup with calm winds and a saturated air mass it develops into fog."

But when the air temperature drops below freezing, it creates a dangerous driving situation.

"When you have temperatures below freezing, you can have fog develop and it will freeze on surfaces and cause an icy glaze," Johnson said.  "The biggest problems would be bridges and overpasses."