Snow explained

Surface snow and wind: what your skis will meet

The snowpack layers explain what is inside the snow. The surface layer, now being built, answers a simpler question: what will my skis meet here at 11:00, and why?

Status

The surface model works as a prototype on one ski area (the 4 Vallées around Verbier) and is not in the app yet. This page describes what it does and what it will show; it will be updated when it ships.

Surface types

Surface	What it means
Soft powder	Light, soft snow your skis sink into.
Packed snow	Settled snow that holds your skis near the surface.
Groomed piste	Prepared piste, assumed groomed overnight.
Wind-packed or scoured	The wind pressed the snow hard or blew it away.
Wind-drifted snow	Snow the wind moved here. It is denser and can feel slabby.
Supportable crust	A firm crust that holds your weight.
Breakable crust	A thin crust your skis can break through.
Spring corn	A frozen base with a softened top layer.
Wet or heavy snow	Wet snow that drags and gets heavier through the day.
Icy or hard	Hard refrozen snow or ice.

"Wind-drifted snow" here describes how the surface skis, not how stable the snowpack is. The avalanche concern "wind slab" stays separate; see wind slab.

Soft snow depth

Alongside the type, the model estimates how many centimetres of soft snow a ski sinks into before it meets a layer that holds it: a firm layer, a crust or ice. Wet snow counts as soft. Snow drifted in by the wind is added and snow stripped away is taken off.

Wind: exposed or sheltered

Each slope gets a wind exposure for the current wind direction, from exposed and scoured to sheltered, where drifts collect, and an estimate of how much snow the wind added or stripped over the last three days.

Through the day

Surface changes faster than the snowpack. A corn slope can be frozen at 8:00, perfect at 11:00 and heavy by 14:00. The surface layer is planned in 3-hour steps for the first two days, alongside the daily snowpack and the hourly sun.

Limits

At 30 m resolution cornices and small wind lips are not visible. The model uses one reference wind per area, so valley channelling is not represented. Pistes are assumed groomed every night. And, as with everything in Snowvy, the surface layer is modelled context, never a judgement that a slope can be skied safely.

Modelled, not an avalanche forecast. Snowvy explains the snowpack; it never says a slope is safe. Read your regional avalanche bulletin and make your own decisions.

Official avalanche bulletins: EAWS (Europe), avalanche.org (USA), Avalanche Canada, and every other official service we know of.

More explainers

• How sun and aspect change the snow
• What modelled snow conditions mean, and what they don't
• Surface hoar: the frost that becomes a weak layer
• Wind slab: how wind loads a slope
• Crusts and facets: why a hard layer can make a weak one
• Persistent weak layers: facets, depth hoar and a weak base
• Wet snow: how warmth, sun and rain change the snowpack
• New snow: what a storm does to the snowpack
• Regional estimate or detailed area: what Snowvy covers where

See it on your slopes