During the GPM pre-launch period physically-based snowfall retrieval algorithms are in an active phase of development. Further refinement and testing of these emerging algorithms requires the collection of targeted ground-validation datasets in snowing environments. This document describes a field campaign effort designed to provide both new datasets and physical insights related to the snowfall process- especially as they relate to the incorporation of appropriate physics into GPM snowfall retrieval algorithms. The referenced field campaign effort is the GPM Cold Season Precipitation Experiment (GCPEx), a collaboration between the NASA GPM Ground Validation (GV) program and its international partner Environment Canada (EC).