There is a growing need for a multispectral smoke dispersion model that can rapidly evaluate concentrations of diffusing obscurant clouds using the modest resources of a personal computer. As different size smoke particles differ in their light scattering properties and their surface deposition rate, the proposed monte carlo lagrangian dispersion model will simultaneously consider a number of particle size classes as well as the initial spectrum of particle diameters. The proposed dispersion model will include state-of-the-art-science modules for lagrangian turbulence estimation, particle velocity estimation, particle trajectory generation, resistance methodology based dry deposition velocity estimation, and efficient computation of concentrations and obscurant attenuation. The project's final report will include a literature review of the relevant topical areas, documentation of the approach used in the various algorithms, preliminary model evaluation, and recommendations for Phase II research.