Freezing Rain or Sleet

With the recent wintry mix, I’ve gotten a lot of questions about sleet and freezing rain. Here’s the skinny. In winter storms, the precipitation starts out as snow several thousand feet up. If it stays cold all the way to the ground, then we see snow. But often the snow falls through a layer of warm air on its way down. If this warm layer extends to the ground, then we get just cold rain. But things get very interesting when there’s a third layer of cold air that the precipitation falls through just before it hits the ground. And the thickness of this cold layer of air just above the ground is what determines if we get freezing rain or sleet. So here’s a look at freezing rain.

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Freezing rain happens when the rain from above falls through a relatively shallow layer of cold air – roughly 1000 feet deep or less. In that case the rain doesn’t have a chance to freeze into tiny ice pellets, rather it freezes where it lands – on trees, power lines, etc. Freezing rain is the worst type of winter precipitation because it accumulates wherever it lands and can cause huge problems.

Here’s a look at sleet.

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Sleet happens when the rain falls through a relatively thick layer of cold air – more than 1000 feet deep. In this case, the rain is in the cold air long enough to turn into ice pellets called sleet. Sleet bounces when it hits the ground and does not stick to what it hits. Sleet can accumulate like snow on the ground, but doesn’t accumulate on tree limbs and power lines like freezing rain does.

 

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