Fall 3D is a serial/parallel (MPI) Eulerian model for the transport and deposition of volcanic tephra developed and maintained at CASE Department of the BSC-CNS. The model solves the advection-diffusion-sedimentation equation using a Finite Differences (FD) explicit scheme and can be used both to reproduce past events and to forecast on-going events (operational mode). The model has a wide community of users worldwide, including academia, research and operational institutions (e.g. the Buenos Aires Volcanic Ash Advisory Center in Argentina).