Klzlllrmak river, with a drainage area of more than 75,000 km2, is the longest river among the rivers which originate and end in Turkey. A coupled atmospheric-hydrologic model based real-time precipitation and flood forecasting system for Klzlllrmak river basin was developed and became operational recently. This real-time forecasting system utilizes the Global Forecast System (GFS) global numerical weather forecasts as the initial conditions and the boundary conditions for the mesoscale atmospheric model WRF (weather research and forecasting) over Klzlllrmak river basin. The WRF regional atmospheric model dynamically downscales the GFS global numerical weather forecasts over Klzlllrmak river basin and provides the initial and boundary conditions to the snow model component of the forecasting system. Details of the atmospheric and snow model components of the forecasting system will be presented separately. Here, the physically based hydrologic model component, WEHY, of the atmospheric-hydrologic model based precipitation and flood forecasting system for Klzlllrmak watershed will be described and some preliminary results will be presented.