Abstract A novel approach for regional climate modeling based on an off-line downscaling of GCM simulations is described and illustrated with a one-month simulation example. The model is physically based and it requires outputs from a previous GCM integration. The methodology is based upon the premise that much of “small-scale” variability (i.e., for spatial scales below current GCM resolution) is often the result of surface forcings rather than small-scale dynamical effects. Following on this consideration, the present work seeks to address the question of regional climate diagnostics by combining precomputed GCM atmospheric large-scale transports of momentum, heat, and moisture, called “the dynamics,” with recomputed GCM subgrid-scale parameterized effect, called “the physics,” including an additional mesoscale forcing term that is parameterized in terms of large-scale flow resolved by GCM coupled with fine-scale geophysical surface fields. This combination is integrated in a prognostic mode on a high-r...