From WindsportAtlanta.com: Wiki
The Wedge is an example of meteorological damming. In the Southeast, it happens when cold air is driven by a NE wind from the Atlantic Ocean or Canada southward. The heavier, colder air pushes against the foot of the Appalachians. The mountains and warmer, southern air aloft keep the wedge confined to the eastern side of the Appalachians but the effect diminishes further south both because of distance and the diminished elevation of the lower Appalachians.
This can cause significant temperature differences by as much as 15-20 degrees between north and middle Georgia. The winds in these conditions can be quite enjoyable 15-25 mph and overcast but can be chilly.
If a more southerly launch is available, it may be worth the drive even if the wind may be a little less. For example, temperatures at Lake Lanier might be in the high 30s while, further south at West Point Lake temperatures will be in the mid-50s.
This weather pattern often precedes severe winter weather as any precipitation from the warm, wet upper level falls through the cooler lower level. If the lower level is below freezing, ice or snow results.