SnowEx is a five year program initiated and funded by NASA THP to address the most important gaps in snow remote sensing knowledge. It focuses on airborne campaigns and field work, and on comparing the various sensing technologies, from the mature to the more experimental, in globally-representative types of snow. The goal is to address the most important gaps in our snow remote sensing knowledge, and thus lay the groundwork for a future snow satellite mission. SnowEx was initiated in the 2016-2017 winter with a field campaign that was designed to evaluate the sensitivity of different snow remote sensing techniques to increasing forest density. In the remaining years, SnowEx campaigns will focus on the efficacy of snow water equivalent (SWE) measurement and modeling techniques in up to four regions of interest: 1. Mountain ranges and temperate forests of the western United States 2. Boreal forests (taiga) and arctic tundra of North America 3. Cold prairies in interior regions of North America, and/or 4. A maritime gradient spanning the Pacific Northwest region of the United States