MM5 is a non- hydrostatic model running once daily at the National Observatory of Athens (0000 UTC cycle). Three domains are used: one covering Europe with 24 km horizontal grid increment, one covering Greece and neighbouring countries with 6 km horizontal grid increment and one over Athens area with 2 km horizontal grid increment. For the execution of the model, initial and boundary conditions data from the U.S-GFS global model are used, kindly provided by the U.S. Weather Service.