What is an anvil cloud?
Anvil clouds, which are mostly ice, form in the upper parts of thunderstorms. They get their anvil shape from the fact that the rising air in thunderstorms expands and spreads out as the air bumps up against the bottom of the stratosphere. You will often see streaks of snow falling out of the edges of anvils. This light snow usually evaporates as it falls through the relatively dry air surrounding the upper part of the thunderstorm.
