Meteorological and Environmental Factors Contributing to Hail Glaciers on the Southern High Plains

Hail producing thunderstorms are a common occurrence on the southern High Plains. On very rare occasions, however, locally excessive hail fall combined with heavy rain has been observed to result in dramatic remnant hail glaciers in the aftermath of severe southern High Plains convective storms. Three hail glacier events have been documented in eastern New Mexico and the Texas Panhandle during the last two decades. During each of these events, localized rainfall amounts of 15 cm to 20 cm contributed to flash floods that accumulated vast quantities of hail to depths of 1 m to 5 m along low-lying draws and tributaries. Resultant hail glaciers have persisted for days, and even weeks, and prompted prolonged closures of roadways. This presentation will document meteorological and environmental factors common to hail glacier events that occurred near Dalhart, Texas, on 9 May 1994; Clayton, New Mexico, on 14 August 2004; and Amarillo, Texas, on 11 April 2012. Commonalities in atmospheric patterns and vertical profiles that promoted high precipitation rates and slow storm motions will be examined, as well as the proximity of intense precipitation to sheetflow enhancing terrain. It is anticipated that documenting these events will help operational forecasters recognize convective modes and storm-terrain interactions that may present a future threat of high-impact flash floods and accumulating hail.