Results of a Heavy Snow Climatology Across
Kentucky and Southern Indiana (1982-1996)

National Weather Service
Louisville, Kentucky

A heavy snow climatological research project at NWS Louisville was conducted between NWS Louisville, NWS St. Louis, and Saint Louis University (SLU). Our specific goal was to develop seasonal heavy precipitation climatologies over the middle Mississippi and Ohio River Valleys. This required review of many past precipitation events in order to develop composite surface and upper-air charts for different types of heavy precipitation producing weather systems during different times of the year. Such climatologies, in conjunction with scrutiny of individual weather systems, are valuable to meteorologists in recognizing overall patterns and parameters that typically are conducive to heavy rainfall and snowfall.

NWS Louisville focused on producing composite charts for heavy snowfall events for Kentucky and southern Indiana. A heavy snow event was defined as 4 inches or more in a 24-hour period covering a sufficient portion of a state climatological region. We produced snow statistical analyses for Kentucky and southern Indiana from 1982-1996, and developed composites of several individual events.

From these composites, at least two significantly different synoptic patterns associated with heavy snowfall across the Ohio Valley were noted. The first pattern consists of relatively weak surface and 500 mb system development. This pattern features a southern stream shortwave within broad southwest flow at 500 mb, a low-level jet and strong isentropic lift ahead of the shortwave, the presence of a jet streak across the Great Lakes with substantial along-stream wind variation in the entrance region of the jet (i.e., winds accelerate quickly into the jet), and frontogenesis across the Ohio Valley within the right entrance region. The northern jet streak also seems to play a significant role in helping hold cold air in place across the Ohio Valley despite warm advection from the south. The second pattern is associated with strong surface and upper-air development, including East Coast snowstorms that can bring heavy snowfall to eastern Kentucky, and slow moving closed off lows and deep easterly flow that can lead to significant snow across parts of Kentucky and Indiana if temperatures are cold enough.

Results from our heavy snow climatological research are presented here.  Click on the links to view research results for the specified events.

Kentucky and Southern Indiana Climatological Regions; Heavy Snow Stats
Individual Event Composite Charts and Summary: January 17-18, 1994
Individual Event Composite Charts and Summary: February 16, 1993
Individual Event Composite Charts and Summary: March 13-14, 1993
Individual Event Composite Charts and Summary: March 20, 1996


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