Results from the Weather Prediction Center's 2023-2024 Winter Weather Experiment

During the past 14 years, the Weather Prediction Center - Hydrometeorology Testbed (WPC-HMT) has led the annual Winter Weather Experiment (WWE). The WWE examines forecast challenges associated with heavy snowfall and mixed precipitation during the cool season, across a variety of scales from mid-latitude cyclones to lake-effect snow bands. This year, the experiment hosted three intensive weeks (two virtual weeks, one hybrid week) focused on evaluating model guidance for heavy snowfall and mixed precipitation events using retrospective cases gathered during the winter of 2023-2024. Participants used WPC-HMT web tools to create their own forecasts of snowfall and freezing rain, and perform subjective evaluations of their forecasts as well as that of convection-allowing model guidance.

In the 14th WWE, participants reviewed deterministic and ensemble forecasts such as those from the Rapid Refresh Forecast System (RRFS), machine learning snow-to-liquid ratio (SLR) guidance, gridded freezing rain analyses, and spatial aligned mean forecast products. During the experiment, we focused on forecasting snowfall and freezing rain events over 24-hour periods at one-, two-, and three-day lead times.

In this presentation, two case studies will be discussed which highlight some key science and forecasting challenges that were encountered during this year’s WWE. The first case was a primarily freezing rain event during 22-23 January 2024 across the Southern Plains and Ozarks. During our evaluations, we reviewed the performance of the experimental Freezing Rain Accumulation National Analysis (FRANA) as well as model freezing rain forecasts that benefitted from post-processing using the Freezing Rain Accumulation Model (FRAM). The second case featured mesoscale heavy snow bands impacting portions of the Ohio Valley and Mid-Atlantic during 16-17 February 2024, where all model guidance struggled to resolve the magnitude and location of the heaviest snowfall. In both cases, we utilized a new sounding viewer display tailored for winter weather forecasting. This presentation will also discuss the usefulness of the sounding viewer in analyzing these cases.