This is tricky because the program (wxsimate) needed to obtain the data for forecasting also normally obtains data from your weather station files which I presume are on your PC. The program would need to gather new data each time you run a forecast and it’s not just GFS it collects. I guess you could run wxsimate on your fathers PC and set it to create the files on the pen drive, then run it on your PC to gather data from your weather station. GFS data is updated 4 times per day at 00,06,12 and 18 hours but the other data it collects may differ in update times. Is there no way to network your two PCs together? Right now I dont have access to my running wxsim or wxsimate to be more specific.
Stuart