Diagnostic and Sensitivity Studies of the 7 December 1998 Great Salt Lake–Effect Snowstorm

Abstract

The processes responsible for the Great Salt Lake?effect snowstorm of 7 December 1998 are examined using a series of mesoscale model simulations. Localized surface sensible and latent heating are shown to destabilize the boundary layer over the Great Salt Lake (GSL) and to produce mesoscale pressure troughing, land-breeze circulations, and low-level convergence that lead to the development of the primary band of convective clouds and precipitation. Model diagnostics and sensitivity studies further illustrate that moisture fluxes from the lake surface were necessary to fully develop the snowband; the hypersaline composition of the GSL did, however, decrease moisture fluxes compared to a body of freshwater, resulting in a 17% reduction of snowfall; latent heat release within the cloud and precipitation band intensified overlake pressure troughing, convergence, and precipitation; orographic effects were not responsible for snowband generation, but they did affect the distribution and intensity of precipitation in regions where the snowband interacted with downstream terrain; and surface roughness contrasts across the GSL shoreline did not play a primary role in forming the snowband. Simulations in which lake-surface temperature and upstream moisture were modified are used to illustrate how small errors in the specification of these quantities can impact quantitative precipitation forecasts, potentially limiting the utility of high-resolution mesoscale model guidance. Results are compared to those from studies of lake-effect precipitation over the Great Lakes, and the implications for operational forecasting and numerical weather prediction are discussed.