Evaluation of Probabilistic Forecasts for Denver International Airport Snow Operations

Accumulating snowfall is a hazard that affects airport ground operations and requires personnel decisions to be made with a day of lead time. The Forecast Impact and Quality Assessment Section within NOAA/ESRL/Global Systems Division collaborated with Denver International Airport (DIA), the National Center for Atmospheric Research (NCAR), and the Boulder Weather Forecast Office (WFO) to evaluate the performance of winter weather forecast ensembles at DIA and similar Mountain West Airports. The Short-Range Ensemble Forecast (SREF) and the High-Resolution Rapid Refresh Ensemble (HRRRE) were evaluated with respect to snowfall, wind speed, temperature, and visibility. Event-based verification of the probabilistic forecasts was performed to look at the total snow accumulation as well as the timing errors of the start and end of the events. The snow accumulation results showed a general trend of overforecasting by the SREF and underforecasting by the HRRRE. Timing errors were significant, particularly for the cessation of snow events. The ensemble results were compared to the forecaster-produced Probabilistic Snow Accumulation Product (PSA), a product produced for DIA by the Boulder WFO. In general, the PSA had slightly better timing than the ensemble model outputs.