A Vision for Probabilistic Winter Weather Services

Winter weather events are costly and disruptive to the nation. Rapid advances in observations, data assimilation and modeling have improved predictions such that some major snowstorms are being accurately forecast a week in advance. However, predictability of these storms varies from event-to event and by scale. Further, specific impacts are more difficult to predict, given that impacts are dependent on variables beyond weather (time of day, road treatment, social response, etc.). The variety of events, associated predictability, and impacts result in a wide range of forecast lead times. These factors challenge decision making. Thus accurately quantifying and clearly communicating the risk of winter weather events is essential to building a Weather-Ready Nation.

The National Weather Service winter weather program is guided by a vision of accurate, probabilistic, and impact-based forecasts. This presentation will express a vision for using probabilistic impact information to drive choices of products and language - using probabilities as the underlying basis for products and communication. For example, basing “Go” or “No Go” watch decisions on the exceedance of probabilistic thresholds, tied to local warning criteria, and eventually to impacts (wind, timing, severity, etc.). The program has embarked on several projects to advance this vision including provision of probabilistic winter weather outlooks, probabilistic snowfall graphics, and impact-focused indices. These projects will be used to highlight the progress and remaining challenges to mitigate winter weather impacts and build a Weather-Ready Nation.