It's Steve here, and I know we've been talking more about chances for periods of freezing rain this weekend, so I thought I'd take a minute to go into more detail about how freezing rain and ice storms form.

Freezing rain is rain that freezes on contact once it hits the ground. What happens is cold below freezing air moves in close to the surface. However, aloft it's still warm and above freezing. As the rain drops fall from that warm above freezing layer into the cold below freezing layer, they get colder and colder. If the rain drops have enough time in the cold air, they will freeze completely before hitting the ground. This is sleet and you can usually hear it ping off the ground or rooftops.

Now, if the rain drop remains cold but liquid...and the ground is below freezing....voila! The rain drop quickly freezes into a coating of ice on whatever it landed, like this tree below.

That's how a coating of ice can form on the roads, sidewalks, power lines, trees and anything it comes in contact with. It's all because of warm air aloft and a shallow pool of below freezing temperatures at the ground.

I hope this helps explain freezing rain a bit more. As of now, the area that could get hit the hardest is West and Northwest of the metro, though St. Louis may see periods of freezing rain mixing with rain both Saturday and Sunday.

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