Climatology and prediction of snow-to-liquid ratio in the central Wasatch Mountains

Predicting snow-to-liquid ratio (SLR) is one of the more challenging aspects of winter weather forecasting, particularly in complex terrain. In addition to uncertainties in quantitative precipitation forecasts, snowfall amount forecasts are very sensitive to the choice of SLR, which exhibits substantial temporal and spatial variability. In many instances, forecasts of SLR have been based entirely on anecdotal climatology or on the typically weak relationship between SLR and surface temperature.

This study involves first using a large snowfall dataset to evaluate various aspects of the SLR climatology at a mountain location. The Collins (CLN) site at Alta Ski Resort in Utah's central Wasatch Mountains provides an ideal study location, owing to a 26-year record of snowfall and liquid equivalent compiled by snow safety professionals. Temperature at crest level and observed liquid equivalent together are found to explain 57 percent of the variance in SLR. Several cases are then given a closer examination through analysis of synoptic and mesoscale features, thermodynamic profiles and radar images in order to diagnose factors responsible for the wide variations in observed SLR. The goal of this study is to develop SLR forecasting methodology for the central Wasatch, which could potentially be applied to other areas of the Rocky Mountains.