The Canadian Avalanche Centre issued a special public avalanche warning for recreational backcountry users who may be intending to enjoy all that new powder this weekend.
Every region in the forecast area with the exception of the North Shore Mountains near Vancouver, and the Yukon, is affected by the bulletin, including the entire Kootenay region. The warning extends to Wednesday, February 26, 2014.
The problem, says Karl Klassen, Manager of the CAC’s Public Avalanche Warning Service, is a weak layer of snow, the result of an extended dry period in January.
“That long drought left the surface of the snowpack in very bad shape,” said Klassen. “Now the new snow is sitting on one of the worst weak layers we’ve seen in a few years.
“That weakness is currently anywhere between one and two metres deep so when it’s triggered, the resulting avalanches are very large.”
Klassen explained that when the surface of the snow is exposed for a long dry period, it changes. With sun and warm temperatures, it melts then freezes creating a smooth, slick surface. Wind on the exposed surface can also form a firm, hard crust.
“Then we got a bit of snow on top of the crust, then it got cold. The snow gets sugary and very weak.”
Klassen says that the new snow most mountain regions have been receiving is heavier and stickier. It bonds into a slab and sits on top of the weaker layer.
“The best analogy is putting sugar on a piece of plywood then putting another sheet of plywood on top. Then put it on a 45 degree slope. The top layer will just slide right off.”
The CAC is urging backcountry recreationalists to use caution in the next few days and exercise conservative decision making.
“There’s a lot of pent-up demand for powder after that dry spell but this weak layer is going to be a problem for the foreseeable future,” says Klassen. “Staying safe will require patience and discipline as long as this layer is in play.”
The weak layer will likely persist after this warning expires, Klassen says, and recreationists are urged to stay cautious in avalanche terrain.
Everyone in a backcountry party needs to carry an avalanche transceiver, probe and shovel and be well-practiced with their rescue skills. The CAC strongly recommends that backcountry users take an Avalanche Skills Training course, and check the avalanche bulletin regularly to keep informed of conditions in their area. More detailed information is also available on the CAC blogs and forecasts at ww.avalanche.ca/cac