A “cool” explanation for the ridge-valley temperature split

Meteorologist Dillon Gaudet breaks down the reasoning behind why the valleys can be much colder than the ridge tops

Have you ever wondered why the ridge tops can be several degrees warmer than the valleys? Aren’t the mountains supposed to be colder? Typically, yes! The mountains in eastern Kentucky are usually colder than the valleys. But on nights will calm winds and clear skies, the valleys can get much colder than the ridge tops. If you are a frequent viewer of Good Morning Kentucky, you may notice me talking about this all the time.

First, on nights with clear skies, temperatures can be much colder than nights with cloud cover. This is because during the day the sun warms up the surface of the earth. When the sun sets of a clear night, the heat absorbed by the earth is re-emitted back into the atmosphere. If there are clouds in the sky, this limits the temperature drop because the clouds act as a “blanket” and don’t allow as much heat to escape back into the atmosphere.

In the mountainous areas, this phenomena is easily noticeable. Temperatures drop in the valleys thanks to clear skies, but colder air on the ridge tops doesn’t stay there. Cold air is dense and because it so dense flows down the mountain slopes into the valleys. It behaves just like water in a sink! The cold air want to “sink” to the lowest point the valleys.

The Kentucky Mesonet sites in Harlan and Pike counties are both over 3000 ft in elevation. The Letcher County site is much lower in elevation, only around 1100 ft in elevation. Wednesday morning there was a 20 degrees temperature difference between the Harlan/Pike County sites and the Letcher County site even though they aren’t that far away from each other.

As always you can tune into Good Morning Kentucky on ABC 36 for more fun science explanations.