Over the past seven years, NSSL and their collaborators have researched the science and technology needed to deploy a real-time storm-scale ensemble system that provides probabilistic forecasts of tornadoes and other thunderstorm hazards on sub-hourly time scales.  This new form of NWP guidance will complement existing operational warnings to enable longer warning lead times and potentially fewer false alarms.  Developing a rapidly-updating high-resolution system that is forecaster-useable is a challenging task.  Current thinking suggests that an ensemble prediction system is needed to facilitate the data assimilation as well as providing estimates of forecast uncertainty.   This talk will outline the core components of the envisioned system and discuss some results from our realtime prediction system running during 2016.  The major scientific and technical barriers that will need to be addressed before operational testing can begin in the early 2020’s will also be discussed.