Analysis of the Record Mesosnowfall Event of 1997 in Central Mississippi

Abstract

Although rare, heavy snowfalls in the southern United States have significant impact and are often associated with distinct surface low pressure systems. However, the central Mississippi record snowfall event of 14 December 1997 displayed mesoscale characteristics and was caused by a rapidly intensifying upper-level system with no surface reflection. Record amounts of unforecast snowfall of up to 8 in. (20.3 cm) occurred. A synoptic and diagnostic analysis of the event determined significant jet streaks, the existence of a middle- and upper-level moisture pool, and a deformation zone with high-level frontogenesis led to the snowfall despite rather unremarkable surface conditions. The system was fully investigated in terms of atmospheric and model diagnostics in an effort to provide clues for an improved forecast. A hindcast simulation of the event using the Pennsylvania State University?National Center for Atmospheric Research fifth-generation Mesoscale Model (MM5) revealed that the use of a mesoscale model in real time may have made a significant difference in forecasts up to 18 h before the event began.