I have a gridded precipitation .dss file that has spatial references “WGS 72” whereas my RAS Mapper projection is set in a “State Plane coordinates”. If I apply this precipitation .dss file in my model, will it automatically transform the dss file into State Plane coordinate?
Yes it should do it automatically. To test it, you can run a simulation, then open RAS Mapper and expand the results “event conditions” and watch the storm generate over your domain.