A Case Study of the 13-14 February 2007 Extended Sleet Event

A major winter storm affected much of the Mid-Atlantic and Northeastern United States on 13-14 February 2007. For an extended and nearly uninterrupted period of 15 hours between approximately 23 UTC 13 FEB and 16 UTC 14 FEB, precipitation in the form of sleet (ice pellets) fell over much of south central Pennsylvania, northern Maryland, and parts of New Jersey. This research investigated the factors contributing to this unusually long precipitation event. The influence of a persistent easterly low-level jet, which helped to maintain a consistent pool of cold air in the near-surface layer, was an important factor in maintaining precipitation in the form of sleet. Temperature and humidity profiles from the NAM, RUC, and GFS were analyzed to determine the mechanism by which this extended sleet was sustained. Bourgouin's method of determining precipitation types was implemented in the model soundings to show that sleet was favorable during the times of interest.