And a Great Day It Was!Posted: March 10, 2010
There were many smiling faces to be seen at Lake Louise yesterday as skiers and riders enjoyed some of the best conditions of the last month or two. The snow was soft and the sun stayed out all day, resulting in a day of skiing that everyone dreams about.
On avalanche control yesterday morning, things moved along quickly. Good visibility allowed control teams to work and travel around the mountain quickly, and the lack of slab conditions in the new snow meant that avalanche propensity was low, avoiding the intensive control work that would be needed if there had been stronger winds and slabs had formed. While the strength of the wind overnight (15-20kph, with gusts up to around 30kph) meant that slabs wouldn’t likely be an issue, it did come from other than the usual direction. Most of the time, Lake Louise gets wind from the southwest, but this storm saw it come in from the north. So, rather than thinking about how slabs may have formed, control teams instead focused on the unusual loading. In other words, a north wind will scour slopes that are usually wind-loaded, and vice-versa. Even thought the winds weren’t that strong, extra caution was required in places like Lipalian Chutes, which are usually scoured but this time had the potential for wind-loading.
As it turns out, the effect of the north wind was visible, but it didn’t really contribute to any elevated avalanche hazard, as the snow was very low-density. When ski cutting some slopes, the new snow would side below us, but not very fast and not gathering much mass. While a slab avalanche propagates out to either side and can widen dramatically from the trigger point, loose snow avalanches don’t widen, keeping to a narrow track as the snow goes downhill, as it did yesterday.
Another advantage of loose, low-density snow (other than making for great skiing) is that it is now available for transport by the wind (called fetch). When the wind does come, skiers can expect a whole different place, and it might be worth watching the wind forecast as much as the snow forecast in the near future.