In July 1992, after several seasons of informal testing, Alaska's interagency fire management community decided to adopt the Canadian Forest Fire Danger Rating System in lieu of continuing to use the US National Fire Danger Rating System. The Canadian Forest Fire Danger Rating System is actually comprised of two primary subsystems or modules-the Canadian Forest Fire Weather Index System and the Canadian Forest Fire Behavior Prediction System. The six standard component outputs of the Fire Weather Index are relative numerical ratings for various aspects of ignition ease, fire persistence and potential fire behavior for a reference fuel type on flat ground, based largely on continuous weather observations.