The negative charge in the lower part of the storm also causes a positive charge to form on the ground. The collision leaves the ice crystals with a positive charge and the snow pellets with a negative charge. When this happens, electrons are stripped off the ice crystals. Ice crystals are lighter, so the updraft carries them up toward the top of the storm cloud.Īs the ice crystals rise and the snow pellets fall, they often collide. The snow pellets tend to fall toward the ground. In a thunderstorm cloud, this condensation becomes either snow pellets or ice crystals. This upward wind is called an updraft.Īs air rises in the atmosphere, moisture in the air condenses into various types of precipitation. Thunderstorms form when warm, moist air rises high into the atmosphere. Lightning comes from charges that build up within a storm cloud.
