The FireLine Assessment MEthod (FLAME) provides a fireline-practical tool for predicting significant changes in fire rate-of-spread (ROS). FLAME addresses the dominant drivers of large, short-term change: effective windspeed, fuel type, and fine-fuel moisture. Primary output is the ROS-ratio, expressing the degree of change in ROS. The application process guides and instills a systematic methodology, utilizing a simple worksheet. The information developed provides a basis for safety judgments and for applying Lookouts, Communications, Escape routes, Safe zones (LCES). The ROS-ratio can be applied to observed fire spread to provide a timeline of future fire spread. Compared to four BehavePlus examples FLAME is accurate to within an average error of 14 percent. In four fireline-fatality cases FLAME predictions match reconstructed ROS-ratios with an average error of 9 percent, and in every case could have foretold the rapid changes that impacted the crews. Adjustment factors are developed to account for variations of windspeed across terrain, and for flame height and sheltering by vegetation. Field application of FLAME is explained and demonstrated with examples.