Once the models have been calibrated for a basin, they can be used operationally with real-time hydrometeorological data to forecast river flows and stages.
The OFS contains three major components that are needed for operational river forecasting:

The Data Entry Component
      is a set of programs that transfer hydrometeorological data
      from a variety of sources to the observed data base.
The Preprocessor Component
      reads raw station data, estimates missing data as required,
      and then uses these data to calculate mean realtime series of precipitation,
      temperature, and potential evapotranspiration for a particular basin.
      These processed time series are used by the Forecast Component to perform
      requested hydrologic and hydraulic simulations.
The Forecast Component
      stores parametric data for the models, as well as information
      that describes the basin connectivity of the river system.
      The Forecast Component also maintains an account of the current model states.
      These states describe the hydrologic condition of the basin including
      the snow cover, soil moisture, and channel storage.
      These states are needed as starting points for subsequent forecasts.