The forget
Isn't hail frozen rain but harder
I shall narrate as a weatherman.
Basically, a hailstone is formed from ice crystals in the upper reaches of a cumulonimbus cloud. The heights required for hail are usually only achieved in mature thunderstorms. The thunderstorm needs to have access to said ice crystals, be able to get them high enough in the stratosphere that they freeze, and have strong updrafts.
The storm has an ice crystal that has frozen from the cold temperatures up in the higher stratosphere. The ice tries to fall to the earth, but it is met by an opposing updraft that essentially sucks air up into the storm as a source of energy. The updraft carries the frozen ice back up into the storm where it picks up more ice and gets bigger. It tries to fall again. If the updraft is still strong, it may get carried back up to add another layer off ice. Then it'll try to fall again. The hailstone just travels in circles falling, rising, layering ice, and falling again until the updraft is no longer strong enough to support its increasing weight, so it just keeps falling until it hits the ground. You can see the layers from each ascent if you cut a hailstone open, just like rings in a tree.
