This data release contains model input and postprocessed model output from a set of numerical simulations of hypothetical lahars initiated on Mount Baker, Washington. We constructed a set of landslide sources near the western summit of Mount Baker and simulated their initiation and downslope evolution into long-runout lahars in the Middle Fork of the Nooksack River. These simulations were conducted in order to evaluate the dependence of lahar dynamics and runout extent on the initial landslide source volume and material properties for hazard assessment. The simulations and encompassing study are described by Gardner and others (2025). Our simulations were performed with the D-Claw model (George and others, 2025), a depth-averaged, two-phase, model for conservation of mass and momentum of granular-fluid mixtures flowing over variable topography. See the accompanying readme.md file for more information about the accompanying datasets. References: Gardner, C.A., Benage, M.C., Cannon, C.M., and George, D.L., Using the D-Claw software package to model lahars in the Middle Fork Nooksack River drainage and beyond, Mount Baker, Washington, U.S. Geological Survey Scientific Investigations Report, 2025. George, D.L., Barnhart, K.R., and Iverson, R.M., 2025, D-Claw - A library for simulation of granular-fluid flows, version 1.0.0: U.S. Geological Survey software release, https://doi.org/10.5066/P13GUXUT.