The two basic forms of multi-scale data assimilation procedures (FDDA), based on Newtonian relaxation, of analysis and observations nudging are applied for a precipitation event occurred over Portugal during summer season. They have been processed employing both TOVS as well as the Portugal automatic meteorological observation network (EMA) data. The mesoscale forecasts were obtained for three integration domains of MM5 model using as boundary and first guess fields the global atmospheric forecast NCEP-NWS/AVN model data. The obtained results indicate that, even using weak FDDA constraint coefficient values, presents a significant improvement in the numerical prognosis in the precipitation field, on both space and time integration levels.