| What it is | Soft round snow pellets (rimed) |
| Forms by | Supercooled droplets freezing on flakes |
| Acts like | Ball bearings when buried |
| Concern | Can be an avalanche weak layer |
From German for 'soft hail' / 'grits'.
Graupel is soft, round, white snow pellets that form when supercooled water droplets freeze onto a falling snowflake (a process called riming), creating little ball-bearing-like grains. It can pile up on the snow surface and, when buried, act like ball bearings as a weak layer that contributes to avalanche danger, so it’s of interest to backcountry travelers.
The ball-bearing snow
A potential weak layer in the snowpack that can feed a slab avalanche, like buried depth hoar.
Frequently asked questions
What is graupel?
Graupel is soft, white, rounded snow pellets that form when a snowflake falls through a cloud of supercooled water droplets that freeze onto it (riming), building up into small, lightly packed balls. It's distinct from hail (which is hard ice) and from regular snowflakes, and crumbles easily when squeezed.
Why does graupel matter for avalanches?
Because its round, pellet-like grains roll and slide easily, like tiny ball bearings. When graupel falls and is then buried by later snow, it can form a weak layer that the overlying slab can slide on, contributing to avalanche danger. Backcountry travelers note graupel as a potential persistent or storm-snow weak layer.
Is graupel the same as hail?
No. Graupel is soft, opaque, and crumbly, formed by riming on snowflakes and associated with cold, often convective winter precipitation. Hail is hard, layered ice formed in thunderstorms, usually in warmer seasons. Graupel falls apart when pressed, while hail is solid ice.
Sources
- Snow grain types — American Avalanche Association
- Weak layers — Avalanche.org