High-Resolution Rapid Refresh Model-Based Climatology and Analysis of Snow Squall Characteristics in the High Plains and Mountain West

National Weather Service (NWS) forecasters have recently been encouraged to issue new warnings for a hazardous weather type, snow squalls. Snow squalls are intense, but limited duration, periods of moderate to heavy snowfall typically accompanied by high surface winds resulting in reduced visibility and dangerous whiteout road conditions. Because this type of alert is new, the frequency and intensity of snow squalls must be studied, and the ability of operational high-resolution models to accurately capture snow squalls needs to be assessed. Due to the shallow convective nature of snow squalls, relatively sparse radar network, and beam blockage by terrain, model guidance will be a key supplement to observations in issuing snow squall warnings given the current Weather Surveillance Radar, 1988, Doppler (WSR-88D) radar network in the High Plains and Mountain West.

Given the relatively small scale of snow squall events, i.e., not captured by global and even some regional numerical weather prediction (NWP) models, we analyze three cool seasons (Sept-May, 2016-2017, 2017-2018, and 2018-2019) of High-Resolution Rapid Refresh (HRRR) model output to develop a climatology of snow squalls and their component hazards, including low visibility, high wind gusts, snowfall, and abrupt surface freezing. Furthermore, we analyze the occurrences of co-located modeled hazard components, measure against known snow squall cases, and investigate the HRRR’s capability to predict snow squalls via the Snow Squall Parameter (SNSQ).