Significant Warming Induced by Downslope Winds near the Smoky Mountains

On 2 January 1999, unexpected warm temperatures were reported across the central East Tennessee Valley with several stations reporting highs around 60⁰F. What made this event unusual was that surrounding sites in East Tennessee reported highs only in the mid 40s with highs only in the lower 30s upwind across the eastern slopes of the southern Appalachians. The warmer temperatures evidently occurred in a narrow band downwind of the Smoky Mountains.

The cause of this narrow band of warm temperatures, some 10 to 15⁰F warmer than surrounding sites, was a strong downslope south-southeast wind off the Smoky Mountains which warmed adiabatically as it descended. This phenomenon is normally observed downwind of mountain ranges, but is typically associated with dramatic temperature rises near large mountain ranges, such as the Chinook winds near the Rockies and the Santa Ana winds near the mountains of southern California. However, significant warming due to downslope winds can also occur downwind of the Smoky Mountains bringing significant (and sometimes unanticipated) temperature rises to localized areas.