Storm snow that increases in density closer to the surface, making it top-heavy.

Fresh snow that accumulates with denser, more cohesive snow on top of looser, lower density snow is described as “upside-down” or “top-heavy.” A storm that delivers denser, slabbier snow on top of low density snow creates the ingredients for Storm Slab avalanches. Upside-down storms are the result of snowfall events that become warmer or windier as the storm evolves. Warmer, wetter, or more wind-affected snow grains quickly coalesce into slabby snow.