Diagnostic and sensitivity studies of the 7 December 1998 Great Salt Lake-effect snowstorm

The processes responsible for the Great Salt Lake-effect snowstorm of 7 Dec ember 1998 are examined using a series of mesoscale model simulations. Loca lized surface sensible and latent heating are shown to destabilize the boun dary layer over the Great Salt Lake (GSL) and to produce mesoscale pressure troughing, land-breeze circulations, and low-level convergence that lead t o the development of the primary band of convective clouds and precipitatio n. 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 fl uxes compared to a body of freshwater, resulting in a 17% reduction of snow fall; . latent heat release within the cloud and precipitation band intensified o verlake 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 wher e the snowband interacted with downstream terrain; and . surface roughness contrasts across the GSL shoreline did not play a prima ry role in forming the snowband. Simulations in which lake-surface temperature and upstream moisture were mo dified are used to illustrate how small errors in the specification of thes e quantities can impact quantitative precipitation forecasts, potentially l imiting the utility of high-resolution mesoscale model guidance. Results ar e compared to those from studies of lake-effect precipitation over the Grea t Lakes, and the implications for operational forecasting and numerical wea ther prediction are discussed.