Earlier today, April 8th, 2020 we talked about a weather phenomenon called cold-air damming. In short it causes our eastern counties to be much cooler than the western counties. If you want to learn more about it cold-air damming click here. Now, we are going to talk about adiabatic heating which warms our eastern counties.
A westerly wind is normally a warm flow for Central Pa. The opposite of a easterly wind. The western counties are cooler compared to the eastern counties, but why? The westerly winds travel over the Appalachian mountains. The westerly winds moves the air up the slopes. As the air rises it cools and condenses. This leads to more clouds over the mountains and western counties. The more clouds there are the cooler the air will be. As the winds reach the summit of the mountain it has one direction to go, down. Forcing the air downward warms and dries out the air. This process is called adiabatic heating. The sinking air is compressed against the mountain and valley and the atmospheric pressure increases. The higher the atmospheric pressure the warmer and drier the air is. The drier air over the eastern counties will allow more sunshine, which heats the air. This is why the towns and cities on the downsloping side of the mountains (eastern counties) are warmer.