Weather Whys: How does hail form?


Southern Colorado sees its fair share of hailstorms throughout the year, especially between late spring and early fall. How does hail form and how does some of it become so large? Here’s a look at how the process works.

First, a storm has to form. That starts off as a simple cloud. Afternoon heating is typically to thank for this. The air at the surface heats up and rises, and with it comes some water vapor. As it rises it condenses and forms a cloud. When moisture is plentiful and the rising continues, eventually that cloud may become a thunderstorm. 

The storm is fed by a warm updraft and releases a cool downdraft as rain and hail fall from the storm. The UPDRAFT is the crucial mechanism needed to create hail.

The top of the storm is very cold–cold enough to freeze water. As the updraft carries water droplets to the top of the storm, they freeze and become small hailstones. These stones fall, then get caught back up in the updraft and move back up to the top of the cloud, collecting more water or even other hailstones as they continue their path through the storm.

A very strong updraft can hold a heavier hailstone. That means more trips through the cloud and a larger end result. A weak storm may not be able to hold up a very heavy piece of hail, so these storms produce smaller hail. 

Eventually the hail will become too heavy for the storm and fall out of the cloud and onto the ground–or your car. 

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