Wind Loading Simulator Overlay

Wind Loading Simulator estimates where snow would build up, and where it would be stripped away, if the wind blew from a direction you choose. Your phone calculates it from terrain elevation data. It doesn't use weather observations or forecasts, so the map shows how the terrain tends to respond to wind from that direction.

Blue areas would collect wind-deposited snow (accumulation), from light blue where the effect is small to deep blue where it's strong. Red areas would be stripped (scouring), from light coral to deep red. Clear areas show little effect either way.

Setting the wind

Use the wind-direction strip on the map to choose where the wind is blowing from. Animated streamlines on the compass show the flow.

When you open an area, the direction starts at a rough estimate of the region's prevailing winter wind, such as northwest in the Alps and Japan or west in the Rockies. That's a long-term average, so check your avalanche or weather forecast for the actual wind and set the direction to match. Wind speed is fixed at about 25 mph (40 km/h).

How the estimate works

Wind strips snow from the side of terrain facing it (windward) and drops it on the sheltered side (leeward). There it often forms a wind slab, a firm layer on top of softer snow and one of the most common avalanche problems in forecasts.

The model reads the shape of the terrain to guess where wind would speed up and where it would slow down. Wind picks up snow where it speeds up and drops it where it slows.

The biggest factor is shelter. For each point, the model looks upwind, up to 300 m, for higher ground that would block the wind. Sheltered spots collect snow and exposed ridges get scoured. Snow scientists use a similar measure, called the maximum upwind slope (Sx), to map wind-drifted snow.

A few terrain shapes add to that. Just past a sharp ridge crest, the wind lifts off the surface and drops its snow, which is where cornices and wind slabs usually form. Gullies running parallel to the wind fill in from their sides. Bumps and convex rolls shed snow, while bowls and hollows hold it.

Loading shows most on 25–45° slopes, the range where wind slabs usually release. Terrain flatter than 8° shows no wind effect.

Limits

This is a simulation of one wind direction at one fixed speed over bare ground. Real wind shifts during a storm, and the model doesn't know the storm history, how much loose snow is available to move, or where trees break up the flow. It also can't resolve features smaller than about 50 m.

It isn't an avalanche assessment. It shows where wind could load snow from the direction you chose, and your local avalanche center's forecast is the place to find out whether those slopes are actually dangerous.

Built from a digital elevation model (DEM). Loading patterns are estimated from elevation data. Rocks, small rolls and gully walls shape real drifts but are too small for the model to see. Use the map to decide where to look, then check for signs in the field like cornices, pillowed snow, shooting cracks and hollow-sounding snow.