Hailstones can have layers of clear and cloudy ice if the hailstone encounters different temperature and liquid water content conditions in the thunderstorm.
And if the supply of water vapor is much larger, the energy released can produce stratosphere-high pillars of cloud with violent updrafts, fierce electrical storms, and grapefruit-sized hailstones.
However, there is much uncertainty in these estimates due to variability in the hailstone's shape, degree of melting, fall orientation, and the environmental conditions.
The hail falls when the thunderstorm's updraft can no longer support the weight of the hailstone, which can occur if the stone becomes large enough or the updraft weakens.