Aircraft observations of the origin and growth of very large snowflakes

A new high‐volume precipitation probe, capable of optically imaging particles up to about 5 cm, was flown in a winter storm during the second Canadian Atlantic Storms Program (CASP II). Dendritic crystals originating aloft in a region of (weak) convective instability were tracked and observed to aggregate into 4–5 cm snowflakes within an isothermal layer near 0° C. The region containing the very large snowflakes was characterized by high radar reflectivities and rapid accumulation of snow at the surface.