The Great Lakes are known to significantly impact the weather of nearby downwind regions. The purpose of this study is to determine the influence of the lake surface on surface fronts and troughs. This study will examine the case of 10 January 1998, when a strong arctic front progressed over Lake Michigan. The impact of Lake Michigan on the front and associated precipitation is examined using supplemental meteorological data from the Lake-Induced Convection Experiment (Lake-ICE) in the Mesoscale Model 5 (MM5). Associated with the arctic boundary was a weak area of frontal precipitation. As the precipitation crossed Lake Michigan an apparent enhancement occurred along the eastern shores of the lake. MM5 simulations will be compared to observations of the case to understand the impacts of the lake on the synoptic scale features. Methods will include with-lake and without-lake simulations to understand the importance of the lake in the simulation. Observations used for comparison with model output include WSR-88D radar images, surface and upper-air analyses, sounding data, and data obtained during the Lake-ICE project.

Results from several with-lake runs of the MM5 indicate that Lake Michigan has a substantial impact on the synoptic scale front. Most importantly the lake slows the progress of the arctic air, alters the local wind field, and also enhances the precipitation downwind of the lake. Also presented in this study are small scale features of the frontal zone such as: frontal structure change as it passes over the lake, boundary layer heat and moisture transport, and amount of precipitation attributed from the lake-frontal zone interaction. MM5 runs with Lake Michigan removed indicate the importance of the lake to the passage of the arctic front.