The compilation of data-parallel languages is traditionally targeted to low-level runtime environments: abstract processors are mapped onto static system processes, which directly address the low-level communication library. Alternatively, we propose to map each HPF abstract processor onto a ``lightweight process'' (thread) which can be dynamically migrated between nodes together with the data it manages, under the supervision of some external scheduler. We discuss the pros and cons of such an approach and the facilities which must be provided by the multithreaded runtime. We describe a prototype HPF compiling system built along these lines, based on the Adaptor HPF compiler and using the PM2 multithreaded runtime environment.