Last week’s warming weather trends concerned Avalanche Canada forecasters, causing them to issue a Special Avalanche Warning for south eastern B.C. and into Alberta.
These conditions, they say, likely caused the very large avalanche that killed a West Kootenay man snowmobiling near Mount Payne west of Kaslo on Thursday, March 4.
“My understanding is the victim was fairly deeply buried and despite the best efforts of his companions who were able to rescue him relatively quickly he did succumb to being buried there,” Avalanche Canada forecaster James Floyer said.
Floyer said the details of the incident were that it took place in fairly high elevation up in the alpine on a west aspect and it happened late in the day.
At that time, Avalanche Canada was tracking rising temperatures, Floyer said it appears consistent with the sun activity and rising temperatures and the avalanche was released on a persistent slab buried up to a metre deep.
“So able to trigger a very large avalanche, pretty consistent with the general pattern of warming that we had been expecting and at that time,” Floyer said. “I think the message was to avoid slopes with sunshine, avoid exposure to large avalanche paths.”
Since last weekend the area has entered a general cooling trend, and Floyer said that the concern for those persistent layers has without question reduced. The further east you travel into the dryer areas, the Purcells and then east into the Rockies, Avalanche Canada still has concerns about something getting triggered on a persistent slab layer.
“The time that we are concerned with that is also consistent with this period of warming really,” he said. “The current cycle that we’re in, we’re in more of a diurnal cycle where sunshine during the day is elevating temperatures in the middle of the day and there’s some sunshine around, that looks like it’s going to be a bit of a theme for this week.”
Temperatures are cooling a decent amount over night, which sets up a pattern where avalanche danger rises towards the middle and the end of the day. Floyer recommends that if you are out in the mountains the start of the day might be the better choice, rather than the end of the day when that heat has entered the snowpack.
There is potential for a little snow on Wednesday, but likely not enough to dramatically alter the avalanche danger, though locally windslabs may be a concern.
Towards the weekend, Avalanche Canada is tracking a large storm which looks like it should hit the west coast, and there is a lot of uncertainty about how much precipitation will move inland from that. Their best predictions currently is that these areas will only get light amounts of snow through the weekend, but if that changes they will update the avalanche forecasts on www.avalanche.ca
“I think it’s fair to say that we’re a lot less concerned about the situation now than we were this time last week, but of course it’s super important to always look for the warning signs of instability,” Floyer said.
These signs are shooting cracks in the snow, “woomphs” and signs of other avalanches in that area. If you see those signs, make sure to back off into lower-angle terrain.