A Climatology of Thundersnow Events over the Contiguous United States

Abstract

A ''climatology'' (climatological description of spatial, temporal, and synoptic characteristics) of snow events with thunder is presented for the contiguous United States. Based upon 30 yr of 3-hourly reports from 204 stations in the 48 contiguous United States, 229 reports are extracted from the 3-hourly observations (consistently bearing the present-weather group in each surface observation) that featured thunder with snow only. When these reports are plotted spatially, the central United States, the intermountain west, and the Great Lakes region emerge as the preferred regions for thundersnow occurrence. A thundersnow event is then defined. Isolated thundersnow reports clearly constitute a thundersnow event. Also, multiple thundersnow reports that are not separated spatially by over 1100 km or temporally by 6 h are considered part of one event. The location reporting the first occurrence of thunder with snow in such a collection of stations then carries the representative time and location for the event. The 229 individual reports make up 191 thundersnow events. Temporal analysis of thundersnow events reveals a nationwide seasonal preference for occurrence in March but no clear diurnal preference. Most thundersnow events are typically reported at only one station and only rarely in consecutive 3-hourly observations. These results thus reinforce the notion of thundersnow as a fairly localized phenomenon of limited duration. In terms of intensity, the thundersnow events investigated in this study feature light snow about one-half of the time, with the remaining events split nearly evenly between moderate (25%) and heavy (23%) snowfall. Further analysis classifies each event according to the meso-to synoptic-scale environment in which it forms. Most events (52%) form in association with a transient midlatitude cyclone; other event types include an orographic class, events that occur with a coastal cyclone, events associated with an arctic front, lake-effect events, and those resulting from upslope flow.

Synoptic scale outbreak of self‐initiated upward lightning (SIUL) from tall structures during the central U.S. blizzard of 1–2 February 2011

“…The 1–2 February 2011 thundersnow cyclone tended to fit the climatology presented by Market et al []. About 53% of U.S. thundersnow reports are associated with cyclones traversing the midcontinental and Great Lakes states.…”

“…Almost all these flashes occurred with deep convection in the warm sector of the intense cyclone. A climatological study by Market et al [] uncovered only 191 thundersnow events between 1961 and 1990. They generally occurred in a broad area from eastern Nevada, the Great Salt Lake region and eastward from Colorado into the central plains, and the Great Lakes states, with relatively few in the southern plains or southeast.…”

The Accumulated Winter Season Severity Index (AWSSI)

“…Changnon et al (2006) established a climatology of snowstorms that is based on station data from across the continental United States, and Changnon et al (2008) connected the snowstorm climatology to a climatology of surface cyclone tracks east of the Rocky Mountains. Hirsch et al (2001) more narrowly focused on a climatology of East Coast winter storms, whereas Market et al (2002) narrowed the focus to thundersnow events. Schwartz and Schmidlin (2002) completed a climatology of blizzard events, providing an analysis of frequency, seasonality, and areal coverage of blizzard events in the continental United States over 41 winters.…”

Cold-Season Thunderstorms in Finland and Their Effect on Aviation Safety

“…A 30-yr climatology of thundersnow events in the contiguous United States was studied by Market et al (2002). Their results show the typical characteristics.…”