Understanding and forecasting tahoe lake-effect snow

Lake-effect snowfall (LES) is common to the Great Lakes region and the Great Salt Lake, but research is limited on its occurrence on Lake Tahoe. Traditional definition and analysis of this process focus on a number of well-established parameters for lake effect development in other regions. These parameters have not been analyzed in detail during Tahoe lake-effect events.This study of five well-defined LES cases on and downwind of Lake Tahoe analyzed parameters and their established thresholds currently in use by forecasters in the region for Lake Tahoe, along with those common to lake-effect snow events in other regions. Parameters discussed included the comparison of lake surface temperature to the 650-hPa temperature, comparison of lake surface temperature to land station temperature, presence of a capping inversion, maximum directional shear in the boundary layer, maximum wind speed in the boundary layer, mean relative humidity in the boundary layer, mean temperature of the boundary layer, thermodynamic instability, and upper level support. Findings confirmed that a number of established LES parameter thresholds do in fact occur in concert with Tahoe LES events. Implications for operational forecasting are discussed.