An objectively developed list of major transition season Northeast snowstorms that occurred during fall and spring from 1983 through 2013 was constructed using National Centers for Environmental Information monthly Storm Data Publications. This list was used to construct composite analyses for categories based on characteristic patterns of lower-tropospheric cold air that coincide with areas of heavy snowfall and to perform illustrative case studies of the categories. The composite analyses and case studies will be used to document the planetary-to-mesoscale flow patterns occurring prior to and during major transition season Northeast snowstorms and to consider the hypothesis that atmospheric rivers play a key role in the formation and evolution of this class of snowstorms. We will address this hypothesis by applying an objective atmospheric river detection algorithm. We also will document moisture transport along parcel trajectories to diagnose moisture sources for areas of maximum snowfall, as well as to diagnose the evolution of selected thermodynamic quantities and moisture variables along the trajectories for selected case studies. While performing the composite analyses and case studies, we will diagnose the processes that contribute to the formation and maintenance of regions of lower-tropospheric cold air that coincide with areas of heavy snowfall.