The Rapid Update Cycle (RUC) is an atmospheric prediction system that consists primarily of a numerical forecast model and an analysis system to initialize the model.

The RUC was designed to provide accurate short-range (0- to 12-hr) numerical forecast guidance for weather-sensitive users, such as those in the aviation community. Significant weather forecasting problems that occur in the 0- to 12-hr range include severe weather in all seasons (for example, tornadoes, thunderstorms, snow, and ice storms) and hazards to aviation (for example, clear air turbulence , icing, and downbursts).

The RUC runs at the highest frequency of any forecast model at the National Centers for Environmental Prediction (NCEP), assimilating recent observations to provide very high frequency updates of current conditions and short-range forecasts.