In a warning that is being hailed as unprecedented, the Canadian Avalanche Centre (CAC) is issuing its third consecutive public avalanche warning for large sections of British Columbia.

The warning area includes the backcountry areas of the North Rockies and the Columbia Mountains, from Mackenzie south to the U.S. border and east of Prince George, Kamloops and Osoyoos. The South Chilcotin Mountains, north of Pemberton, are also included.

“Three warnings in three consecutive weekends is unprecedented,” said Karl Klassen, the CAC public avalanche bulletins manager in a news release. “Several weak layers in the upper snowpack are proving to be very persistent and show no sign of improvement.”

The warning went into effect immediately on Monday (March 8).

Klassen said one of the main reasons for the unusually dangerous avalanche conditions has been the comparatively light and sparse snowfalls over the past several weeks.

“The weather really drives everything,” said Klassen. “Typically we’ll get snowfalls of 40 to 50 to 60 cm every week or every couple of weeks. This winter, it’s just been so dry and those larger dumps of snow have been few and far between.”

The smaller amounts of snow mean that the white stuff in the upper levels of the snow pack is not compacting and stabilizing. The snow that has been falling on top of the snow’s surface hoare — surface hoare is a feathery type of ice that is essentially the winter version of dew — is not enough to crush it down and stabilize it. This means that each of the five to six layers of 10 to 20 cm snow is now sitting on top of partially crushed ice which is highly prone to slipping.

The lower amounts of snowfall meant that three weeks ago, the avalanche danger in the warning area was potentially dire for people on foot, skis or snowboard, but a snowmobiler might be able to ride out of an avalanche, said Klassen.

However, that appears to be changing. Because the smaller snowfalls have been accumulating over the past several weeks, the mass that could slip has reached more deadly sizes.

“We started out with high probability and low consequences, then we moved into medium probability and medium consequences and now it looks like in a few more days we’ll have a better idea, but it looks like a low probability, high consequences situation,” said Klassen.

Still, Klassen said that the base snowpack in the warning region is extremely stable right now, which means that the more destructive slab avalanches are not as likely to happen this year as they were last. The problems in the snow right now are generally in areas closer to the surface. Last year was a different case.

“I’ve been working in this area for 32 seasons now, and last year was the worst that I can ever remember,” said Klassen of last year’s base, which was more granular, crusty and unstable. Those avalanches broke away deeper in the snow and were heavier and denser than this year’s snowslides. Still, while the 2008/2009 avalanches had the power to destroy hectares of forest and this seasons only have enough to destroy a pickup truck, both ultimately have the power to kill a person.

Steve Blake, a public safety specialist with Jasper National Park, said that the geography and weather patterns in the Jasper region mean that there is not as much snow here as the mountains to the west.

“The main reason is that we are on the east side of the continental divide,” said Blake. Blake said, typically, the mountains to the west of Jasper receive most of the weather blowing in from the Pacific Ocean. The fact that Jasper is located on the leeward side of the eastern Rockies also means that snowfall here is not as large as areas in the west.

 “Snow that we get here is typically preceded by wind and that can have the effect of blowing away any surface hoare,” said Blake.

All of this means that conditions for avalanches in Jasper right now are very different and not as dangerous.

Blake said the snow that fell on Monday, March 8 in Jasper would create more dangerous avalanche conditions compared to last week. That hazard is most increased in site specific locations, such as solar aspects, steep alpine lee areas and around ridge features.

The danger will go up in general out on the mountains, but “generally speaking, this snow should create a bond with the existing snowpack,” said Blake.

 “You might find more dangerous conditions in a specific place, but it’s going to be highly localized.”

The CAC is urging backcountry recreationists in the mountains in Northern British Columbia to stay away from avalanche terrain until the snowpack becomes more stable.