Integration of a Road Surface Model into NWS Operations

According to the U.S. Federal Highway Administration, severe winter driving conditions are responsible for more than 1,300 fatalities, 100,000 injuries, and $2.3 billion in spending by state and local agencies annually. To mitigate these losses, both community leaders and the public require increased awareness of the potentially threatening conditions so that they can prepare accordingly. There is ample motivation for the NWS to pursue new approaches toward identifying high-impact road weather events in advance, and communicating relevant information to the public: the NWS 2011–2020 Strategic Plan highlights the need for increased decision support services (DSS) to community leaders, and public safety has always been at the heart of the NWS mission.

Currently, a winter storm warning is issued when specific meteorological criteria are likely to be met (e.g., 6 inches of snow in 12 hours). However, the impact on the community involves more than just the snow amount, but whether or not the snow will stick to road surfaces and affect traffic. Approaching this issue requires a physical model that resolves interactions between moisture, such as frozen precipitation, and the road surface. This objective information can be used to augment the forecast, providing better information to the public and possibly increasing forecaster confidence in issuing warnings on meteorologically weak, high-impact events.

During the 2011–2012 cool season, a number of NWS Western Region offices spent time evaluating the performance and operational usefulness of the Model of the Environment and Temperature of Roads (METRo). This model resolves the road surface conditions at a point based on site-specific metadata, past conditions, and a gridded atmospheric forecast. Based on a limited verification study, the model is shown to be quite reliable at depicting road conditions under various meteorological scenarios, and appears best at temperatures near 0°C—initial results will be presented. During the 2012–2013 cool season, METRo use will be expanded to a larger number of forecast offices throughout Western Region, paving the way for a more extensive verification of model performance.