Hexagonal or star-shaped snowflakes; a potential weak layer

Credit: The International Classification for Seasonal Snow on the Ground / JSSI

Stellar dendrites are what most people think of when they picture a snowflake. They resemble a star with six arms extending from their center. Their arms and side branches can be fragile. Plates are thin simple hexagons. Both of these crystals have smooth, planar surfaces that can bond poorly to the snow that surrounds them. As atmospheric conditions evolve throughout a storm cycle, layers of stellar dendrites or plates can form a weak layer beneath accumulating slabs of storm snow.  

Magnified view of a plate. Credit: CalTech

A cluster of stellar dendrites.  Credit: Universities Space Research Association

Credit: The International Classification for Seasonal Snow on the Ground / Greene