Learn
The basic terms behind the 3D view, the colours and the layers on this site. This is a starting point — it does not replace a proper avalanche course.
Slope angle
Most slab avalanches start on slopes of 30–45°. What matters is the steepest part, not the average. Slope here is measured on the true terrain (DEM); the 3D height exaggeration is visual only and does not affect the angles.
Aspect
The compass direction a slope faces. It drives both sun (south-facing warms through the day) and wind (snow piles up on the lee side). The picture changes with elevation and time of day.
Wind-loading & wind slab
Wind strips snow from the windward side and deposits hard slabs on lee slopes. The site’s wind layer uses forecast wind direction only, and feeds the risk colour only when the wind is strong enough to move snow. It is not a substitute for the bulletin’s rose.
Avalanche danger (1–5)
A 1–5 scale from Low to Extreme, issued by the official avalanche bulletin. “Low” does not mean safe. The site never fetches the danger for you — you read the bulletin and enter it.
Terrain complexity (the ATES idea)
Simple / Challenging / Complex describe how many options you have to avoid danger and how exposed you are to overhead terrain and traps. Our label is auto-derived from slope — not a qualified, official ATES classification. Every Yotei route sits toward Complex.
Terrain traps
Gullies, creeks, cliffs and trees — features that make even a small slide far more serious. The same volume of moving snow is much more likely to bury or injure you over a trap.
Reading the bulletin rose
The rose shows, at a glance, which aspects and elevation bands hold which avalanche problem at which danger. Coloured sectors are the combinations to be wary of. Read the rose and the problem type (storm / wind / persistent weak layer, etc.) before you trust any colour on this site.
For real learning, take an avalanche course (AST / JAN), carry and practise with a beacon, probe and shovel, and travel with experienced partners or a guide.