Q: I heard a weather forecaster talk about thundersnow. What is thundersnow?
A: Thundersnow is the rare combination of thunder and lightning within a snowstorm, says Prescott Bishop of Texas A&M University. “This phenomenon occurs when a deep convection within a snowstorm allows the clouds to extend high enough for an electrical charge to develop,” he explains. “Although thundersnow can occur along storm fronts, it is more often associated with lake-effect snow, making the Great Lakes the prime region in the United States for thundersnow to occur. In Texas, most thundersnow storm events have been observed in the Panhandle, especially around Lubbock and Amarillo. Thunder in a snowstorm is more difficult to observe than in a rainstorm because the snow muffles the rumble to where it can only be heard within a radius of a couple miles.”
Q: Why is thundersnow so rare?
A: When a deep layer of solid and liquid droplets form within the cloud, an electrical charge develops, but this deep-mixed layer has difficulty forming during snowstorms, Bishop adds. “First, convection that produces this mixed layer is much less common during snowy conditions because the cold temperatures at the surface lead to a more stable atmosphere that resists strong upward motion. Furthermore, although liquid droplets can still exist within clouds when temperatures are below freezing, temperatures at the surface cannot be too far below the freezing point, otherwise the liquid content of the cloud will not be sufficient to produce lightning. For this reason, thundersnow usually occurs when there is wet snow, meaning that rain is mixed in with snowy precipitation.”
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Weather Whys is a service of Texas A&M University’s Department of Atmospheric Sciences.
