From local impacts to country-wide warnings: progress and challenges of developing an operational impact-warning chain

Severe weather poses significant threats to society, necessitating the development of effective forecasting and warning systems to mitigate their impacts. Integrating impact-based forecasts into warnings, with the premise of reducing peoples harm, currently consists in a paradigm change for many national weather services. Being at the intersection of probabilistic forecasts, uncertainty analysis and state-of-the art risk modelling, this new paradigm also entails significant challenges.This contribution presents the ongoing efforts at MeteoSwiss to incorporate impacts into weather warnings. Through collaboration with stakeholders, including first responders and local authorities, MeteoSwiss is initiating a local pilot project focusing on heavy precipitation and deployment planning in the canton of Zurich. This impact case study, tailored to specific locations and use case, serves as a pilot to learn for further development and scaling up of impact-based warnings.Furthermore, as a national-scale counterpart, we work on establishing a quasi-operational demonstrator for Switzerland, which integrates impact proxies (hazard-exposure) rather than full-fletched impact computations. We address the trade-offs inherent to developing impact-based warnings, including the need to balance data availability, specificity and utility across varying warning scales, and the need for seamless integration within an operational weather service.This contribution discusses potentials and draw-backs of integrating many-dimensional impact considerations into weather warnings from the perspective of a national weather service, highlighting the importance of interdisciplinary collaboration and stakeholder co-development, and demonstrating the use of impact modelling tools in a (quasi-)operational context, with the ultimate aim to better cater to the diverse needs of society in the face of severe weather events.