The Winter Storm Severity Index: Forecasting and Communicating Winter Hazards

The U.S. National Weather Service’s (NWS) mission includes providing impact-based decision support services to its core partners for the protection of lives and property. Unlike traditional forecast products that focus on accumulation totals, the NWS Weather Prediction Center (WPC) has developed a cutting-edge impact-based winter forecast product – the Winter Storm Severity Index (WSSI) – to translate the forecast to societal impacts. The WSSI is a suite of operational forecast tools that integrates the official gridded forecast data with climatological and non-meteorological information to create a situational awareness forecast tool that communicates the location, timing, and severity of anticipated societal impacts from winter hazards.

WSSI classifies impacts for several winter hazards including snow and ice accumulations, blowing snow, and snow load. Impacts captured in the WSSI include but are not limited to: impacts to transportation, damages to vegetation, disruptions to utilities, damages to infrastructure, and the overall disruption to daily life. Accurate depiction of the societal impacts from winter weather hazards involves an interdisciplinary approach that leverages not only improved forecasts but new and existing research on how winter hazards interact with the natural and built environment. This presentation will include: 1) An overview of the WSSI suite of products (i.e., the deterministic and probabilistic operational versions, in addition to hourly and probabilistic hourly products in development), 2) Examples of how the WSSI scientists and developers approach improvements and additions to the underlying algorithms, and 3) Examples of how the WSSI product is used in the field with forecasters and core partners.