This paper addresses the issue of developing weather-impacted routes for the Final Approach Spacing Tool (FAST). FAST relies on adaptation data that includes nominal terminal area routes and degrees of freedom to generate optimum landing sequences and runway assignments. However, during adverse weather some adapted routes may become unavailable due to the presence of hazardous weather. If FAST continues to generate trajectories using these routes, its schedule will not be accurate during the adverse weather. The objective of the study was to determine methods for incorporating severe weather products and weather-impacted route data into FAST.