Thundersnow is a captivating meteorological event where lightning and thunder occur during a snowfall. This phenomenon, often described as a winter thunderstorm, is a rare occurrence. Its infrequent nature distinguishes it from more common weather events.
Understanding Thundersnow
Thundersnow is essentially a thunderstorm where the precipitation falls as snow rather than rain. The fundamental processes driving thundersnow are similar to those of a summer thunderstorm. It involves the presence of unstable air, sufficient moisture, and a mechanism that lifts this air, leading to charge separation within the clouds.
However, in thundersnow, these conditions develop in freezing temperatures. The snow tends to muffle the sound of thunder. This can make the thunder sound more like a low rumble than the sharp crack heard during a typical summer storm, and it often does not travel as far.
The Specific Conditions That Create Thundersnow
Thundersnow is rare because the specific atmospheric conditions required for its formation are less common in winter. For lightning and thunder to develop, a relatively warm and moist layer of air must exist near the ground, situated beneath a colder air mass aloft. This creates atmospheric instability.
Strong updrafts lift this moist air rapidly into colder atmospheric regions. This rapid vertical motion, combined with a steep temperature gradient (known as a lapse rate), allows for significant convection within the snow-producing clouds. Within these clouds, collisions between ice crystals and graupel particles separate electrical charges, resulting in lightning. These conditions are infrequently met in winter because the atmosphere contains less energy and moisture than in summer. Specific triggers can include lake-effect snow, where cold air passes over warmer water, or synoptic forcing within large extratropical cyclones.
Frequency and Geographic Patterns
Thundersnow is globally uncommon, with its occurrences often highly localized. Precise global statistics are not extensively documented due to its sporadic nature. On average, fewer than 10 thundersnow events are reported worldwide each year. Some estimates suggest that only about 7 out of every 100,000 thunderstorms are thundersnow events.
Certain regions experience thundersnow more frequently. Areas near large bodies of water, such as the Great Lakes, are more prone to it due to lake-effect snow, which provides the necessary atmospheric instability. Mountainous regions and parts of the Midwestern United States, the Northeastern United States, the British Isles, the Sea of Japan, and elevated areas of Israel and Jordan also report occurrences. Even in these areas, thundersnow remains an unusual sight.
What It’s Like to Experience Thundersnow
Lightning flashes illuminate the falling snow, creating a brilliant, ethereal glow against the dark winter sky. This reflection off the snowflakes can make the lightning appear brighter than during a typical rainstorm.
The accompanying thunder often sounds distinct. Instead of a sharp crack, it sounds like a deeper, more prolonged rumble. Dense snow acts as a sound dampener, muffling the thunder and causing its sound to dissipate quickly, often only audible within a two to three-mile radius of the lightning strike. This combination of bright, silent flashes and distant, rumbling sounds creates an unusual and memorable atmosphere.