The GO (grid operations) model of the U.S. Western Interconnection is being developed to address weather and water dynamics and associated vulnerabilities in this bulk power system. The grid ops model is currently based on a synthetic 10,000 node topology of the U.S. Western Interconnection developed by Texas A&M University (TAMU). The user pre-specifies a subset of key nodes within this larger network, selected based on proximity to major load centers, generation and transmission assets. Then a reduced (simplified) topology is produced and associated model version instantiated. Several attributes have been added by the grid ops team that make it attractive for use within IM3: 1) Open source, publicly available Python code base that can be transferred to other systems of interest; the core model code has already been transferred to a substation-level, DC flow model of the North Carolina grid. 2) Capabilities for hydrologic-mass balance simulation of major Federal and non-Federal hydroelectric dams in the U.S. Western Interconnection. 3) Capabilities for linking with a wide range of climatological and hydrometorological datasets and simulation models, as well as other key modeling efforts within IM3 (e.g. BEND/TELL and CERF). 4) Capabilities for tracking multiple performance metrics, including total system operating costs, locational marginal prices, and carbon dioxide emissions, as well as code for post-processing diagnostics and uncertainty/sensitivity analysis.