A special avalanche warning has been issued for most of British Columbia and parts of Alberta.
Issued Thursday morning by Avalanche Canada, the warning is for recreational backcountry enthusiasts and is in effect until Monday, March 4.
“Recent storms have deposited a significant amount of snow across western Canada,” Avalanche Canada said in its warning.
“This new snow sits on prominent weak layers established during drought conditions in February. In some areas, there is more than one weak layer.
“As the active storm period passes, widespread natural avalanche activity will slow. However, human-triggered avalanches remain likely.”
Avalanche Canada says it’s been tracking those weak layers for the past month, and that vary from region to region, but it’s a serious issue.
“While their structure has different forms across different regions, the result is the same — highly problematic layers that remain reactive to human triggering,” said Avalanche Canada forecaster Tyson Rettie.
Last weekend, a man died while snowmobiling in southwestern Alberta. And on Monday, a man snowmobiling near Revelstoke, B.C., was rescued after being buried by an avalanche.
“Recreationists should not underestimate the instability of these weak layers or their potential to produce large avalanches,” Avalanche Canada said.
“Although the new snow is appealing, making conservative terrain choices will be an important strategy for all backcountry users over the next few days.”
Rettie says the key to understanding storm-slab avalanches is knowing about layers.
He says as new snow falls, it’s more likely to bond with itself than the layer it’s falling on. The result is a firm layer of snow atop an older layer.
“We call this a slab and with just the weight of the new snow accumulating, you can eventually get that to release as a slab avalanche, sliding on the old surface,” said Rettie.
He also noted that a slab avalanche can trigger other avalanches on nearby slopes.
If you’re determined to head into the backcountry, Avalanche Canada suggests sticking to lower-angled slopes, avoiding overhead hazards, and choosing smaller objectives to minimize the consequences of an avalanche.
“This has been the biggest storm of the season, and we know backcountry users are eager to enjoy the snow,” Rettie said. “But it’s vital to not underestimate the instability of these weak layers. Any avalanche triggered on them could be deadly.”
“Given the unpredictability of avalanches, and their devastating potential consequences, we’re urging everyone to stay safe by exercising caution and making informed decisions when planning a trip in the backcountry,” said Bowinn Ma, B.C.’s Minister of Emergency Management and Climate Readiness.
More information about avalanches, including forests, is available online at Avalanche Canada.