Wednesday, 16 April 2014

Spring Snow Safety in Western Newfoundland

By Keith and Heather Nicol
      When ski touring in the spring we need to be aware of snow safety if we travel in avalanche terrain. If you are not sure if your planned  route is traveling in areas where avalanches might occur you can check out the on line maps which show potential avalanche start zones in Western Newfoundland. This map ( highlights areas that are between 30-45 degrees which are the typical slopes needed to get avalanches moving. Simply click on the start zone symbol and if you want to see where avalanches have occurred in the past you can click on the avalanche symbol. You can zoom in and out on the map and you can also move around to different areas in Western Newfoundland. As you can see there is lots of areas where avalanches can start but there is also great low angle ski touring that can be done in this area if you want to avoid avalanche terrain altogether.
     However, many backcountry skiers and snowboarders want to ski steep areas in the Tablelands or Blow Me Down Mountains and if you do you need to think about how to manage the various snow safety hazards. In a typical Newfoundland spring  there are 4 different types of hazard ranging from cornice fall to loose wet snow avalanches as well as wet slab and wind slab avalanches to consider. Cornices may fail at any time but in the spring the risk goes up as the temperature rises above 0 C. Cornices not only are dangerous in themselves but they might also trigger avalanches on the slopes below as shown in the photo below from the Tablelands. So give cornices a wide berth when skiing above and below them especially on warm days.
A large chunk of cornice that also triggered an avalanche (note debris up slope)
      Wet loose snow avalanches are common in the spring in Western Newfoundland and the adjacent photo shows several in Blow Me Down Bowl. These avalanches are generally not too hazardous on an open slope but they do pack more punch than you might think. They can often knock a skier or rider down and if there are rocks or trees downslope they can possibly be injured. To manage this risk avoid start zones when the snow is wet from the sun, warm temperatures, rain or does not freeze overnight. 

Large loose snow avalanches in Blow Me Down Bowl
      Wet slab avalanches are more of a hazard than loose snow avalanches since they involve more snow and will likely travel faster. They occur when water percolates into the snow layers and triggers an avalanche. The photo below shows one that occurred in the Tablelands Bowl. Although this slide was only 30 cm deep in most places it did pile up to 1.5 meters in others and was an estimated 80-100 meters long. To manage this risk avoid start zones when the snow is wet from sun and warm temperatures, rain or does not freeze overnight. 

Wet slab avalanche in Tablelands Bowl
Wind slab avalanche

      Wind slabs tend to occur where fresh snow has been deposited on lee slopes. Since we likely will not get much new snow through the rest of this spring this hazard is not that likely but if we do get a spring snow storm then be aware of where the wind may have piled this snow up. Also since it likely will fall on an icy crust this creates a good layer for this snow to slide on.  Since we get most of wind from the west this hazard can be managed by avoiding steep east slopes where wind slabs are most likely to have been created. 

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