An Assessment of High Impact Sub-Advisory (HISA) Snowfall Events and Efforts to Improve Forecast Communication

Winter weather season across the midwestern United States has a multitude of forecasting challenges, including lake effect snow banding, cold air outbreaks, ice storms, and blizzards. With major winter storms commonplace across the region, events such as a 1-3 inch snowfall tend to receive less attention by the public. A short duration, yet high intensity snowfall of fewer than three inches can still be dangerous and lead to instantaneous whiteout conditions and rapidly changing road conditions. These snowfall events, referred to as “high impact, sub-advisory” (HISA) by DeVoir (2008), remain a major forecasting and communication challenge today. The focus of this research is twofold, first a climatology of sub-advisory level snowfall occurrence will be conducted across the midwest utilizing six hourly snowfall totals and WSR-88D data. Secondly, a survey of members of the weather enterprise, including National Weather Service forecasters, broadcast meteorologists, and emergency managers will be conducted. The goal will be to understand how forecasts for these “sub-advisory” snowfall events are currently communicated. In addition, during the 2017-2018 winter season, post event surveys will be conducted to assess the effectiveness of the communication methods utilized. Preliminary results of these surveys will be presented. Findings from this research seeks to help develop new guidelines for identifying when these types of events are possible and how to better communicate the risk to the public to reduce their overall impact in the future.