The Transformation of the National Weather Service’s Winter Storm Outlook

The National Weather Service’s (NWS) Winter Storm Outlook (WSO) is an experimental product produced at the Weather Prediction Center (WPC). The product currently depicts the probabilities of exceeding Winter Storm Watch/Warning Criteria for snow or freezing rain across daily periods from Day 1 through Day 4, as well as a 4-day maximum, utilizing the WPC Winter Storm Ensemble. The WSO has been a publicly accessible product since December 2019 and has undergone several minor modifications since inception. While initially the WSO was primarily used for NWS internal watch and warning considerations, it is beginning to gain usage in external briefings and partner decision making.

The WSO is one tool of many within the NWS winter product suite and one of several national-scale outlooks that is available for public consumption. These outlooks are probabilistic, impact-focused products that have consistent application and approach across the country, and provide for national readiness and awareness by giving increased lead time to partners and the public.

The NWS Winter Program identified that a seamless Day 1 to Day 7 National Winter Storm Outlook is necessary for Impact-Based Decision Support Services and that the current WSO is not completely serving this purpose. The program formed an internal working group to develop and deliberate on science and societal-based options for how this product should evolve to provide the best public service. Two proposed solutions were developed as a result of this working group. The first is a risk matrix based on the Probabilistic Winter Storm Severity Index (PWSSI), which distills the entire suite of probabilistic data into simple, tiered risk levels. The second proposal depicts the probabilities of exceeding Moderate impacts for snow and freezing rain using the PWSSI.

To help further validate and select the future framework for the WSO, the Winter Program began work with the NWS Social, Behavioral and Economic Sciences team. Focus groups and surveys were developed and are underway to assist in determining which product is more useful, actionable, and understandable, as well as determining how the public and partners interact with probabilistic data, color scales, and category names. This presentation will describe the considerations that are informing the transformation of the Winter Storm Outlook.