I have running a real case with 5 nested domains (the third first one normal, the last one LES). Because it was so slow, I just ran the 2 first domains (3 km and 1 km dx/dy). The terrain is mountainous and I use the best resolution available for meteo and DTM. However, even with 2 domains it takes ages and I have no idea why. I tried several combinations of parameters without success, and use 1 way nesting now It seems that the radiation scheme is a problem so that I chose radt=60 even if my time steps is 1. Could you help me identify what causes the run to be so slow and how I could improve it? Thanks for your help.