Backdoor cold fronts & cold air damming

Why won’t the clouds budge and why has the temperature had trouble rising much of the day? It could be a backdoor cold front or cold air damming.

We’re used to the typical cold fronts that move from west to east or from northwest to southeast but what about the cold fronts that come in from the east or northeast? Those in New England and the Mid-Atlantic, among other areas, are all too familiar with these pesky fronts.

The backdoor cold front carries winds out of the same direction – east or northeast. They occur when a high-pressure circulation – clockwise – pushes cold air south and west. For New England and the Mid-Atlantic, this means cooler and moist air moves in off the Atlantic onto land, replacing the warmer and more dry air mass.

These back door cold fronts can also occur north of an area of a developing low pressure.

Cold air damming, or CAD, is also common thanks to a low-level high-pressure circulation, usually over the eastern Great Lakes and interior Northeast. As the cool layer of air moves easterly, it hits the Appalachian Mountains. Cold air is dense and cannot rise unless heated so it stays put on the eastern side of the mountain chain like in New York City, Philadelphia, Baltimore or Frederick, Md., Richmond, Va., or Raleigh, N.C.

It is also possible on the eastern side of the Colorado Rockies including places like Denver or Boulder. The same setup of high pressure is required.

During the spring, many are wanting to get outdoors in these areas to get the garden started, participate in sporting events, or even just enjoy the warmth. But when a backdoor cold front or cold air damming occurs, these activities may have to be postponed!