Beyond The Forecast: What is 'The Wedge'/Cold Air Damming?

The wedge, also known as cold-air damming (CAD) is cold air that funnels down the east coast into the Carolinas and at times when it is strong all the way into northeast Georgia, metro Atlanta and central Georgia. While CAD can form out west it is more common in the eastern United States and southeast. CAD set ups can make for difficult forecasts because temperatures can be colder than expected and CAD set ups can cause ice storms. Cold air damming occurs when cold dense air gets wedged against the windward side of the Appalachian mountains. CAD events can result in freezing rain and ice events across the Carolinas and at times in parts of Georgia. Freezing rain can occur when moisture from the Gulf Of Mexico comes in over the top of the cold air at the surface. As the rain falls into the layer of cold air the atmosphere can moisten up and then evaporative cooling can occur. As moisture rises the temperature can fall. Not every CAD even causes ice but when it does cause ice it can be catastrophic. CAD events can occur sometimes in the summer but are more common in the Fall and Winter. Sometimes it can just hold temperatures down and make for a chilly cold day. Many times in the Fall a CAD event has just a plain cold rain but in the winter a CAD event can contribute to a ice storm.