The accurate forecasting of the form of precipitation in wintertime storms (e.g. rain, snow, freezing rain) is a challenging problem with potentially great societal benefit. The Principal Investigator will investigate the factors that determine precipitation form and its impact on the structure of the parent storm. The study will include a climatological effort, diagnostic and numerical modeling studies. Particular emphasis will be placed on the study of snow that falls at temperatures above zero degrees centigrade. Such storms cause great damage and present forecasters with formidable problems.