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Ask the Meteorologist: Rain vs. Snow

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How is it cold and rainy? Shouldn’t it be snowing?

Ashley Falleur

Rogue River

 

The four main types of winter precipitation are rain, snow and the “in betweens” or sleet and freezing rain. The type of precipitation that falls solely depends on the temperatures of our atmosphere.

Obviously when our entire atmosphere is warm, rain will fall and the same goes for snow — when our entire atmosphere is cold, snow will fall. But this is not the case when we see sleet or freezing rain. Let’s say for instance, there is a warm layer a few thousand feet above the surface. All precipitation falls as snow, but when it passes through this warm layer it will melt depending on the depth of the warm layer. If there warm layer is shallow, the snowflake will melt, and then partially refreeze through the colder temperatures at the surface.

With freezing rain, the snowflake falls through a deeper layer of warm air. In this case, it melts completely and then will freeze on contact with the ground if temperatures are at or below freezing. It also can freeze through a very shallow surface layer of cold air.

So, rain can fall when there is very cold air at the surface (near freezing) if most of the atmosphere is very warm aloft!

 

Meteorologist Alyssa Caroprese