How Early Winter Snow Conditions Affect Avalanche Danger
By John BufferyFor years I’ve reflected on the season just past and realized that the best days always seem to come in the early season-that moment of raising your arms and dropping in on the very first day, the summer’s yearning satiated instantly with gasps of whirling vapor trails.
Early snows consist of super cold, large, edgy crystals that are bonded (consolidated) with each other or with the surface they rest on. There’s only a thin, white blanket covering the terrain that hides sticks and stones to break your bones. This newer snow doesn’t have enough weight to compress those first couple of snowfalls and help consolidate the base snowpack. It might take over a meter of snow on a slope before there’s enough accumulation to worry about an avalanche (unless the mountains are super smooth, like glaciers or the shale slope on Whistler), but to keep it safe, it’s best to ride where the snow is deepest. Shallow areas can be a catalyst to the first part of an avalanche-the collapse of a thin, weak layer.
Pay Attention To Relief: Convex Slopes Versus Concave SlopesThe ground relief is more visible early season. Convexities (rollovers) are exaggerated, causing more tension at the break over. This tension point would be the “sweet spot” for starting an avalanche on a slope-not such a problem if you ride in the thicker snow depths of concaved (curved-in) basins.
Know Your Aspects
In the early season, mountain aspect plays an important roll in deciding what’s rideable. Cold, northerly facing snow preserves a fairly weak bond. Early season south slopes have a warmer snowpack-the sun’s angles are influential, but not too strong yet. This solar-affected snow has a more consistent, stable snowpack early season. However, these factors will reverse later in the season as the sun becomes stronger.
At the beginning of winter, I try to remember all the significant storms and weather events that are lying on the mountain from the past few weeks. I’ll pay attention to the most important character of each storm-noting things like wind slabs on north slopes or sun crust on south ones, or even something as detailed as a surface hoar on the ridge tops.
While you’re out early season, look at the snow three dimensionally. Dig profiles up high and see how those first couple storm layers are bonding to each other. Compare your compression test to your Rutschblock tests, and then compare those with your friends’ observations. If this is where you play, then these are things you should have some information on. You might even want to take a course to gain some ideas on how to make good decisions.
As always-ask, tune in, turn on.
Go to Avalanche.org for links to avalanche-forecasting centers in your area and listings of locally available avalanche courses.