As the warm moist air travels around the center of lowest pressure, it overrides colder air located North of the low and is cooled to its saturation temperature, producing rainfall and snow. Snow generally occurs with East winds, since the winds at locations north of a mid-latitude cyclone are from the East. Close-up photograph of a snowflake. Snow pellets are white, spherical grains of ice 2 to 5 millimeters in diameter. They can be distinguished from packed snowflakes since snow pellets are firm enough to bounce when they hit the ground.
Snow pellets develop as supercooled droplets freeze on ice crystals.
They may fall for a brief period as the precipitation changes from ice pellets to snow . The large downdrafts in mature thunderstorm clouds provide the mechanism for hail formation. Hailstones normally have concentric shells of ice alternating between those with a milky appearance and those that are clear. The milky white shells, containing bubbles and partially melted snowflakes, correspond to a period of rapid freezing, while the clear shells develop as the liquid water freezes much more slowly. Hail stone measuring 21 centimeters.