Very rare, but not impossible: Be Prepared for Lake/River Effect - WAFF-TV: News, Weather and Sports for Huntsville, AL

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Very rare, but not impossible: Be Prepared for Lake/River Effect Snow

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(Source: Amy W.) (Source: Amy W.)
(WAFF) -

The simple explanation for how lake or river effect snows forms is when cold air masses move over warmer lake or river waters.

As the warm water heats the bottom layer of air, lake or river moisture evaporates into the cold air.

Since warm air is lighter and less dense than cold air, it rises and begins to cool. The moisture that evaporates into the air condenses and forms clouds, and snow begins falling.

What makes this forecast so tricky and can yield snow amounts ranging from a dusting to 4 inches over just a few miles is the wind. It has to be the perfect direction.

On Feb. 9, a west-northwest wind blowing directly over the Tennessee River and Wheeler Lake produced a few hours of moderate snow downwind, in northern Morgan and Marshall Counties.

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