VANCOUVER -- Avalanche Canada is warning backcountry skiers to stay away from mountains in the Sea-to-Sky corridor Friday as "very large avalanches are almost certain."

A series of intense storms is headed toward the South Coast bringing rain and heavy winds, which will further destabilize heavy layers of weak snow.

"There are multiple weak layers buried deeper in the snowpack, including a variable layer of surface hoar and crust from mid-December (down 70-90 cm) as well as a deeper layer of sugary facets and crust buried in late-November (down 120-200 cm)," reads a bulletin on the agency’s website.

"Both of these persistent weak layers produced many large and destructive avalanches over the past few weeks."

An extreme warning for that area is rare, but avalanche forecasters are confident that "large destructive avalanches will be widespread."

Forecasters also warn against traveling in runout zones since they believe the avalanches can reach as far as the valley floor.

Avalanche danger