Weather Influences on Snow Safety and Avalanches— Temperature
Temperature has a profound effect on avalanche safety. Quite often the basic rule of thumb is to finished early by starting even earlier. That way you achieve your mission before the sun starts having adverse effects on the snowpack.
When we start to investigate temperature influences we need to think of temperature as heat transfer. We can isolate those heat effects into three main areas. The snow surface, the interior of the snowpack, and the ground. This heat is moved or transferred between those areas typically due to for example external factors such as cold air, warm air, and sunshine.
Before we delve deeper into heat transfer let's look at the most basic of temperature considerations for splitboarders or ski tourers
Basic Temperature Considerations
Let’s review the most basic safety principles of temperature considerations for splitboarders or ski tourers.
Considerable warming — It is very critical, but its effects can be easily evaluated and quite often observed.
Slow to moderate warming — Helps to set the snow cover and the bond between the layers created a more stable snowpack.
Warming during day, cooling at night — Causes the snow cover to compact perfectly (Melt-Freeze), yet attention must be paid to the avalanche situation deteriorating during the course of the day from east to west. If further new snowfalls after a cold spell, a critical layer can form.
Cold — Preserves existing risks and delays the setting process. Extreme variations between the temperature of the ground and the air can promote the formation of unstable layers due to Facet formation. More issues are often observed on north-facing slopes due to the lack of direct sunlight to assist in the settling process (Rounding).
For those looking to dive in deeper, let’s review the key heat transfer zones.
Heat Transfer at the Snow Surface
Heat can be transferred at the snow surface by conduction, evaporation, condensation, radiation, and precipitation. Quite often two or more processes are occurring at once.