A terrain feature that is curved or rounded like the exterior of a sphere or circle, i.e. goes from less steep to more steep. Convex slopes generally tend to be less safe than concave slopes, but concave slopes can also avalanche.
Whether a slope is concave, convex, or planar makes some difference in avalanche danger, usually not a significant difference. Avalanches happen on any steep slope without thick anchors despite the shape of the slope. Slope shape makes more difference on smaller slopes than on larger ones.
Convex slopes statistically produce more avalanches and more avalanche accidents than other kinds of slopes, partly because they are inherently less stable and partly because they present more safe travel problems than other slopes.
• Convex slopes have less compressive support at the bottom than other slopes, which makes a difference for small avalanche paths, some difference on medium sized avalanche paths but has little effect of large avalanche paths.
• Convex slopes tend to wind load more than other slopes. (Wind slows down as it rounds the convexity which causes it to drop its load of snow.)
• Convex slopes are tricky to descend because each step or turn you take adds another degree of steepness until suddenly you find yourself on terrain that’s too steep. But you can also use this to your advantage. With a soft slab, if you descend slowly, especially jumping on the snow or slope-cutting while you descend, the avalanches tend to break at your feet instead of above you more so than on planer or concave slopes. (Remember that hard slabs tend to break above you no matter what.)
• Convex slopes are difficult to assess because the conditions you find on the upper flat part of the slope often are much different than on the steepest part of the slope where you will most likely trigger an avalanche. For instance, there are some stories in which someone digs a snow profile on the upper section, pronounces the slope safe, then triggers an avalanche on the steeper part below. To assess the snow it is better to dig on different slope that is similar to the slope you plan to ride but is smaller, gentler and poses little avalanche risk.
• When descending a convex slopes they are difficult to exit if you start to find dangerous conditions. You have to climb back up. All too often people would rather risk their life by descending than to climb back up.
• Probably the most dangerous shapes are double convexities–convex vertically and horizontally–like dropping off the edge of a basketball. These slopes tend to wind-load both from the top and from the side, they have no compressive support and are very difficult to descend, ascend or cross safely.