They are interpolated to many sites around the Great Lakes. The new data sets are extremely well tailored for the prediction of lake-effect snow because they provide the high degree of temporal and vertical resolution necessary to evaluate such mesoscale events. These severe winter storms develop as a result of very cold air passing across the relatively warm waters of the lakes during the late fall and winter months. The flux of heat and moisture from the lake creates convective instability in an otherwise stable airmass. The prevailing wind helps to channel the moisture plume and subsequent precipitation in narrow bands downwind of the lakes.
Orographic features tend to enhance the precipitation process.
The storms are truly severe convective weather events that disrupt travel and commerce and at times can be life threatening. Although the storms are roughly on the horizontal scale of summertime convection, they are confined to a much shallower layer in the lower atmosphere than the typical summer thunderstorm. The mature storms frequently develop into steady-state features, often existing for prolonged periods of time over one location until a change in the overall synoptic pattern modifies the environment around the storm. For this reason the evolution of these mesoscale events can be forecast with some degree of accuracy, if the synoptic scale conditions are well predicted. The data sets proved their worth almost immediately.