What impact? Communicating Severity Forecast Information through the Winter Storm Severity Index

Communicating the threat of severe winter weather is not simply a matter of the quantity of inches of snow or degrees of cold; it also considers the potential impacts of the storm. The Winter Storm Severity Index (WSSI) is a graphical product from the National Weather Service that presents anticipated impacts from forecasted winter weather for a range of winter conditions. To assess the utility of the WSSI and how an impact-based winter weather forecast product is interpreted and used to inform decision-making, a mixed-methods social science study was conducted by the Nurture Nature Center in coordination with the Weather Prediction Center. Through focus groups and surveys, testing in the hydrometeorological testbed, and iterations on design and category descriptions, several themes emerged about how professional stakeholders understand, interpret, and use this product for communicating about impending winter weather. There is perceived utility in the WSSI for situational awareness and as part of a package of other information to inform decision-making. However, there is variability in interpretations of impacts, resulting from differences in geography, community readiness and experience, among other factors, which creates complications in communicating the forecast. Further, many users seek quantities related to winter weather, suggesting that education about what impact-based products include and what data are shown is necessary. Understanding the factors that influence perspectives on impact levels, and the variable needs for winter weather information across regions, improves forecasters’ abilities to effectively communicate and provide critical information that helps end users prepare for severe winter weather.