Winds that encounter mountains are forced upward to ascend the mountains. The air expands and cools as it rises, forming clouds. As the air continues to rise, raindrops form and fall from the clouds. This process, known as upsloping or orographic lifting, causes mountainous locations to get heavier precipitation than lower elevations. If upsloping occurs in a cold airmass, the precipitation will fall as snow.

As air rises up the mountain, it cools and condenses, forming clouds.

Water vapour continues to condense, rain falls from clouds.