Saturday, January 13, 2007

Saved by the Cold

So far, Central Missouri has been spared the worse of this latest winter storm. Ironically, this is because we were covered by more cold air than areas to our south and east. As a result, we have received an inch or two of sleet but have had very little freezing rain.

As the warm, moist air from the Gulf over-rides the dense, cold Arctic air, precipitation is triggered in the higher layers. If the lower, cold layer is thick enough, this rain freezes before hitting the ground, producing a sleet storm; sleet can make travel difficult but, since it bounces off trees and wires, it does not cause significant damage or power outages. On the other hand, if the cold zone is relatively thin, the rain does not freeze until it strikes the trees, wires, ground and roadways. Such freezing rain can be disastrous, bringing down tree limbs and power lines as the ice builds up on these structures. Sleet never looked so good!