What is it about?

On 26 March 1999, an unexpectedly heavy and complex snowfall event occurred across the southern Appalachian region. This event was unusual in that it produced a narrow band of heavy snowfall (10-15 cm or 4-6 inches) downwind of the Smoky Mountains. This snowfall event was complex in that lift from frontogenesis, mountains, cold air damming, and waves combined to produce the heavy snowfall amounts across the entire region.

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Why is it important?

An interesting aspect of this snowfall was the waves observed on satellite and radar imagery during the initial stage of the event. These waves developed in the lee of the Smoky Mountains as a strengthening southerly wind flow became nearly perpendicular to the Smokies. It appeared that these waves contributed to the heavy snowfall amounts by providing additional lift to the larger scale lift already present.


This heavy snowfall event caught forecasters in east Tennessee by surprise, and was unusual in that the heavy snowfall occurred in a narrow band directly downwind of the Smoky Mountains.

David Morris Gaffin
National Weather Service

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This page is a summary of: An Unexpectedly Heavy and Complex Snowfall Event across the Southern Appalachian Region, Weather and Forecasting, April 2003, American Meteorological Society,
DOI: 10.1175/1520-0434(2003)0182.0.co;2.
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