A widespread public avalanche warning is in effect for mountains across southern B.C. and Alberta — for both backcountry terrain and more accessible areas.

The region has seen a significant dump of snow over the last few days, with more than 120 centimetres falling in some areas. The new snow is sitting on top of a weak layer, which makes the snow more prone to slides, according to Avalanche Canada.

Several avalanches have already occurred in the last few days, in areas that are historically prone to slides.

On Saturday, for example, a CP freight train was struck by an avalanche in Glacier National Park. No injuries were reported.

The avalanche forecasting organization — along with Parks Canada and Alberta's Kananaskis Country — is warning anyone heading into the mountains to take safety precautions.

"You're not going to get any warning signs until it's too late," said Ilya Storm, forecast program supervisor.

"Conditions, especially in the coastal mountains, are very different from what you're used to."

The public safety warning affects several popular winter destinations in B.C. and Alberta. (Avalanche Canada)

The public warning applies to these regions:

Sea-to-Sky.

South Rockies.

South Coast Inland.

Kananaskis Country.

Purcells.

Banff-Yoho-Kootenay National Parks.

Lizard Range-Flathead.

Waterton Lakes National Park.

The danger rating for the regions ranges from high to considerable, depending on the area and elevation, which means the terrain is described as dangerous and human-triggered avalanches are likely.

Avalanche Canada publishes a daily avalanche bulletin online that rates the danger in specific regions based on likelihood and expected size. (Avalanche Canada)

Storm says the clear weather in the forecast for the upcoming week is a concern as more people may be heading out to the mountains during the Christmas holidays.

"Way more people are heading to the hills — there's been a big storm, it's powder days," he said.

"There are a lot of things pulling people out there right now."

It's not just those exploring the backcountry who need to take precautions, he said. Popular summer trails that are used for winter hiking or snowshoeing are also exposed to avalanche terrain.

The heavy fresh snow sitting on top of a weaker layer underneath makes it more likely to slide with the slightest of triggers, Storm said, and it's going to be a continuing safety concern.

"We've got a problem in the snow pack that isn't going away any time soon," Storm said.

"It's going to linger for days, weeks and possibly even months."

Anyone venturing into the backcountry should carry essential avalanche gear like a transceiver, probe and shovel, according to Avalanche Canada, but travel in high risk areas is discouraged regardless of safety equipment.