What is "cold air damming"? - | WBTV Charlotte

What is "cold air damming"?


Saturday was far from the prettiest day we've seen this year.  Clouds, rain, fog and drizzle dominated the forecast with a similar pattern in place today.  What's causing this yucky weather?  It's a wedge of cold air stuck east of the mountains.  This is known as cold air damming.

This is something seen in many locations east of a mountain range all over the world.  Cold air gets wedged or dammed on the eastern side of a mountain range and leads to a chilly, cloudy, yucky forecast that can linger for days.  

Let's take a closer look at what happens in the Carolinas.

For us, cold air damming occurs when we have high pressure over the Northeastern US.  Since wind always blows clockwise around high pressure that bringing us a Northeasterly wind that contains cool, moist air.  Cool air is dense and since it doesn't rise, it gets bottled up on the east side of the Appalachians.  The effect is amplified when we have low pressure to our south or southeast.  

Then we have another layer of warm air that rides up over the cold air due to its lower density.  As that air rises, it cools and condenses and a thick layer of cloud cover forms.  Those clouds usually produce light rain and drizzle.  This will keep temperatures well below normal.  In the winter, this can result in freezing rain or sleet, creating a huge mess.  In the summer, it brings a cool, damp and icky day or two to the forecast.

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