Within the troposphere, where most of our weather takes place, temperatures usually get colder with a rise in elevation, just as you would expect during a hike to the summit. A reversal of this normal behavior happens during temperature inversions, also called thermal inversions. When skies are clear and winds are low, oftentimes under high pressure, daytime heating slows and stops as night falls. Air at the surface cools more quickly than it does aloft, especially in low-lying areas, like mountain valleys. As the warmer heated air from the daytime rises, cooler denser air remains and becomes trapped underneath the “cap” of warmer air aloft until the next morning when heating resumes or a new air mass mixes in.

 

In the case of last weekend, neighboring valleys had cold, light, northern air flowing down with ample snow cover and clear skies, which allowed for radiational cooling overnight. The buoyant warm layer of air aloft kept the denser, colder air near the surface until it began to warm through the morning with ample sunshine under the exiting high, as demonstrated above by our Current Summit Conditions with Auto Road Vertical Profile, showing the range of temperatures on Jan. 22 at 9:43 a.m. EST.  

 

I took full advantage of the resulting prime conditions at the summit, enjoying a walk outside and talking with some hikers who remarked how much warmer it was than when they started out that morning. The temperature difference from the valley to the summit was about 25 degrees Fahrenheit! This set up a perfect morning to take photos while visibility was on my side at about 120 miles.