This archive contains supporting data and modeling software for a study testing use of the STC-MODSCAG fractional snow-covered area product as forcing data for the AI-based M4 water supply forecasting model. The study was performed by S.W. Fleming, K. Rittger, C. Tagliatela, and I. Graczyk. The M4 code archive here is a clone of the Natural Resources Conservation Service National Water and Climate Center's GitHub public repository for M4 (https://github.com/nrcs-nwcc/M4) as of February 2024, including code, example problems, and a user manual.