A few years ago, when traffic was stalled for an entire weekend in the southern cities of Atlanta and Birmingham by a mere 2 inches of snow, we Northerners laughed. But the reality is we Northerners are not so good at driving on our own snow when it falls early in the fall, and it is not just a matter of "getting used to it" again.

When the temperature of the ground is significantly warmer than 32 degrees, and a burst of snow falls just as the air and ground temperatures drop below freezing, the half-melting snow freezes on road surfaces and creates a treacherous icy layer underneath the accumulating snow.

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For most of a Northern winter, the ground temperature is below freezing, so this flash-freeze doesn't happen. But under just the wrong circumstances, which are far more common during a Southern winter, road conditions can be so bad there is no way to safely drive a car.