Over the holidays, I went back to eastern Ohio to visit my folks. And that meant taking the Pennsylvania Turnpike. The drive can sometimes be amazing because of the weather changes that come with crossing the Appalachians.

The weather was fairly uneventful on the way out - the only thing that struck me was the temperature change. At the highest point along the turnpike, at an elevation of around 2600 feet, it was a good 10^oF colder, a temperature difference in line with what’s average, a 3-4^oF drop for every 1000 feet you go up.

On the way back, though, the weather was much more changeable. Snow showers were scattered across Western Pennsylvania, aided by west winds which rose up the Appalachians - and rising air forms clouds. So near the highest peaks, I was crawling in low visibility on a snow-covered road. But just a half hour later heading down the mountains, the snow ended and the sun even broke out - a textbook lesson that when those west winds moved downhill, the clouds and precipitation tend to dissipate. And the rest of the drive was smooth sailing.