What is thundersnow?

Thundersnow is a relatively rare phenomenon in which a winter thunderstorm produces precipitation in the form of snow rather than rain. The storm develops from ingredients much the same as those that create thunder and lightning in a rainstorm, but when there is cold air in the mix, rain becomes snow.

The rarity of thundersnow is due to the unlikely combination of all of the ingredients necessary to produce it. Generally speaking, you won't have the combustible combination for thunder during an average snowfall. Whereas within the unstable air masses that interact to produce typical thunderstorms, you are unlikely to have the cold air required to change precipitation from rain to snow. It is an extremely uncommon occurrence to witness all of the circumstances lining up just right to create thundersnow. It generally forms inside a cold portion of an extratropical cyclone.

Weather is never perfectly predictable, so when an alert is broadcast, it is essential to pay attention. While rare, thundersnow can be dangerous. You should be alert to many of the same dangers that would be present in a thunderstorm itself. Snow can diminish the sounds of thunder and muffle the awareness of its presence, thereby putting you at risk for lightning strikes. Another danger, of course, comes from the threat of driving in icy conditions. It's safest to stay indoors and off the roads when thundersnow is in the forecast. Essentially you are preparing for both a severe thunderstorm, as well as snowfall.

The Great Lakes area of the United States is where you are most likely to experience the thundersnow phenomenon. Conditions tend to be more favorable there than in any other location on earth. This is because lake-effect snow falls for a longer period. While still unusual, with only about .07% of snow found to be accompanied by thunder, this area is most likely to have the necessary components available to create the situation. Other regions known to report occasional thundersnow include Nova Scotia, the Rocky Mountain area of Colorado, as well in early spring near Montana. Mount Everest has reported thundersnow, as well as areas near the Sea of Japan, northwestern portions of Europe, and even in the Western Mediterranean. Theoretically, anywhere that has the potential to experience snowfall in winter or thunderstorms at any time of the year, can experience thundersnow, should all the required meteorological conditions come together just right.

A thundersnow event is not something you see every day. It is a spectacular display of the power of nature. While unique by any standard, it is especially remarkable considering how unlikely it is to witness all of those ingredients intertwine to produce this storm. With the snow potentially absorbing the sounds of thunder and the flash of the lightning, keep tuned to local weather if thundersnow is mentioned in your forecast.

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