An overview of thundersnow

Lightning and thunder are commonly observed during the warm season from cumulonimbus clouds. These thunderstorms may be accompanied by heavy rain, hail, strong winds, and possibly tornadoes. During winter, however, snowstorms with heavy snowfall can occasionally produce lightning and thunder. The combination of snow and lightning/thunder is called ‘thundersnow’ (Figure 1). For example, two notable thundersnow events have struck the United Kingdom. On 28 January 2004, a strong cold front and squall line passed through much of southern Britain, producing thundersnow, hail, gusty winds, and a tornado at Coombe Down, Bath. The wet snow froze, causing numerous traffic problems during the evening rush hour. In another example, during one six-hour period of convection on 3/4 January 2008 in Belfast, Northern Ireland, 12–15 centimetres of snow fell. One lightning strike disabled a substation in Lisburn, causing 13 500 homes to be without electricity, according to the TORRO database. The United States is not immune to thundersnow either. An early-season snowstorm, named ‘Aphid’, struck Buffalo, New York, on 12 October 2006 yielding cloudto-ground (CG) lightning strokes at rates of 10+ strikes per minute during the height of the storm. Another event occurred a few months later on 1 December 2006 in Columbia, Missouri, when more than 38 centimetres of wet snow fell overnight, with a period of lightning and thunder between midnight and 1 a.m. The metro area was paralyzed the next morning by the heavy snowfall. In the USA, only 1.3% of cool-season (October–May) thunderstorms report incidences with snowfall, and only 0.07% of reported snowfalls are associated with lightning or thunder (Curran and Pearson, 1971). Thus, thundersnow is an exceptionally uncommon event. In addition, thundersnow storms generally produce fewer lightning strokes than thunderstorms with rain during the warm season. For example, in one thundersnow event in Utah during 2002,