Thundersnow

[3] Thundersnow also occurs in Nova Scotia and in the Northeastern United States, especially in New England and New York, sometimes several times per winter season.

[6] The British Isles and other parts of northwestern Europe occasionally report thunder and lightning during sleet or (usually wet) snow showers during winter and spring.

Scotland registered an episode of thundersnow in the early hours of 4 December 2020, the unusual noise causing alarm among local people.

[8] Western Europe has rare occurrences of thundersnow, as on 8 March 2010, when northeastern Catalonia, including Barcelona, experienced a heavy snowfall accompanied by lightning, with snow depths surpassing 30 centimetres (12 in) in low altitude areas.

[citation needed] Thundersnow is caused by the same mechanisms as regular thunderstorms, but it is much more rare because cold dense air is less likely to rise.

[15] Lake effect thundersnow occurs after a cold front or shortwave aloft passes over a body of water.

It is generally accepted that at this temperature there is no longer any super cooled water vapour present in a cloud, but just ice crystals suspended in the air.

This allows for the interaction of the ice cloud and graupel pellets within the storm to generate a charge, resulting in lightning and thunder.

The best location in a storm to find thundersnow is typically in its NorthWest quadrant (in the Northern Hemisphere, based on observations in the Midwestern United States), within what is known as the "comma head" of a mature extratropical cyclone.

Similar to the lake effect regime, thundersnow is usually witnessed in terrain in the cold sector of an extratropical cyclone when a shortwave aloft moves into the region.

The shortwave will steepen the local lapse rates, allowing for a greater possibility of both heavy snow at elevations where it is near or below freezing, and occasionally thundersnow.