This article presents a high-resolution, impact-based early warning system (FEWS) for riverine flooding, demonstrating its capabilities through a comprehensive hindcast of the 2021 European Summer Flood in the Ahr River basin, Germany. The system integrates near-real-time hydrodynamic and impact forecasts, providing valuable information for local authorities and civil protection agencies to make informed decisions and initiate effective emergency responses. Key components of the FEWS include ensemble precipitation and water level forecasts, probabilistic predictions, and high-resolution inundation maps with associated uncertainties. The study highlights the importance of integrating impact forecasting into operational FEWS, addressing challenges such as computational efficiency and uncertainty propagation. The results show that the proposed system can provide crucial timing information and enhance disaster preparedness, offering a 17-hour lead time for informed actions. The effectiveness of the system is validated through comparisons with official forecasts and emergency mapping products, demonstrating its potential to improve flood management and reduce socio-economic impacts.This article presents a high-resolution, impact-based early warning system (FEWS) for riverine flooding, demonstrating its capabilities through a comprehensive hindcast of the 2021 European Summer Flood in the Ahr River basin, Germany. The system integrates near-real-time hydrodynamic and impact forecasts, providing valuable information for local authorities and civil protection agencies to make informed decisions and initiate effective emergency responses. Key components of the FEWS include ensemble precipitation and water level forecasts, probabilistic predictions, and high-resolution inundation maps with associated uncertainties. The study highlights the importance of integrating impact forecasting into operational FEWS, addressing challenges such as computational efficiency and uncertainty propagation. The results show that the proposed system can provide crucial timing information and enhance disaster preparedness, offering a 17-hour lead time for informed actions. The effectiveness of the system is validated through comparisons with official forecasts and emergency mapping products, demonstrating its potential to improve flood management and reduce socio-economic impacts.