I quickly learned that in the time I lived over there. The only cold wind direction is NE, any southerly wind obviously doesn't bring in cold air, and N & NW is downsloping air that has been severely modified because of the smokies.
One interesting observation from last week though was the front and disturbance that brought ice to Memphis and points north, that front was oriented almost 90 degrees because of the waves along it, hence ice on the backside vs snow. When the front passed by our winds shifted WSW and actually brought the cold air in from that direction. It was a rare occurrence that doesn't happen very often bringing the cold air south of the apps, then east.