Seasonally Changing Patterns of Lake-Effect Snowfall in Western Lower Michigan

Abstract

A shift in the area of maximum lake-effect snowfafl?toward Lake Michigan from an early season inland location between November and January and a return inland by March?over western lower Michigan was investigated for the period from November 1965 through March 1971. The seasonal pattern for all areas of western lower Michigan was similar, but the inland displacement of early- and late-season snowfall was nearly twice as great in the northwest section. Lake-snow days were identified and daily maps analyzed to determine the axis of maximum snowfall the displacement from the lakeshore was measured along three traverses, one each in southwest, west-central and northwest lower Michigan. Temperature differences between the lake water and air at the 850 mb level and geostrophic winds at the surface, 850, 700 and 500 mb levels were calculated over mid-Lake Michigan, and observed winds for Green Bay, Wisc., and Flint, Mich., were determined for each lake-snow day. The degree of inland displacement of lake-effect snow was strongly related to wind speed at the surface and the 850 mb level. At a given wind speed, a greater lake surface ?850 mb temperature contrast was associated with snowfall nearer the lakeshore, and wind speed upstream at Green Bay was more closely correlated with lake-snow patterns than was the wind speed downstream at Flint.