Coastal regions are dynamic interfaces that often feature high populations, complex infrastructure, and tight connections between biological productivity, ecosystem health, and economic security. As part of the Department of Energy (DOE) coastal research modeling initiative with the vision to improve Earth system prediction, we conducted a scoping endeavor focused on the Puget Sound region - a coupled Earth-Human coastal system with sharp mountain-to-coast hydroclimatic gradients interacting with strong urban-to-rural land use gradients. A multi-pronged, integrated approach was taken to this scoping effort that included a pre-scoping literature review and a community engagement workshop held in March 2022 to bring together scientific experts to review the current state of knowledge; identify gaps in modeling capabilities, measurements, and data; and define key research needs and next steps. Here we present the findings from this scoping effort, including the identified challenges and future research opportunities in modeling Puget Sound Earth-Human system dynamics considering extreme events such as atmospheric river, heat wave, drought and flood, as well as the influence of climate variability, climate change, and evolving human system dynamics in the Puget Sound region.