VANCOUVER -- People are being warned to avoid all avalanche terrain in the Sea to Sky region tomorrow, as the risk of slides is expected to climb to extreme in alpine areas and at the treeline, according to Avalanche Canada.

According to the organization’s website, "very large avalanches are almost certain on Friday as intense precipitation will form large storm slabs and add tremendous stress to an already weak snowpack."

Avalanche Canada advises avoiding all avalanche-prone terrain in those conditions. The rating below the treeline is expected to be high starting Friday, and the ratings for all levels of the Sea to Sky region are expected to be high by Saturday.

Avalanche Canada forecaster Colin Garritty said there’s a weak layer buried deep in the snowpack in that part of the province, and anywhere from 40 to 100 centimetres of new snow is expected there between Thursday night and midday on Friday.

"That’s a situation that could definitely produce some very large avalanches that could be quite threatening to people who are travelling in or near avalanche terrain," he said.

Squamish Search and Rescue Manager Tyler Duncan told CTV News Vancouver the situation is like "adding a card on top of an unstable house of cards."

"This storm coming in is loading that already hazardous snowpack with a lot more snow at higher elevations, which causes it to be more unstable," said Duncan. "The extreme rating is basically saying that human-caused and natural avalanches are certain, so it’s gonna happen."

On Friday, the avalanche danger rating for alpine areas on the South Coast is expected to rise to high and will remain that way through Saturday. The rating means avalanche conditions are "very dangerous," with natural avalanches being likely and human-triggered avalanches "very likely."

Avalanche Canada’s website said most of the South Coast will see more rain than snow, but heavy rain could create the potential for "wet, loose" avalanches.

North Shore Rescue avalanche forecaster Peter Marshall said his team is definitely expecting a rise in avalanche danger, with the strong weather system arriving Thursday night.

"Most likely the highest avalanche hazard’s going to be overnight, with lower danger (Friday) morning," he said, and added conditions can also change quickly. "We are expecting a series of weather systems to be coming in over the next several days, so avalanche danger will increase again if we get more snowfall falling on the snowpack."

Marshall said anyone heading into avalanche terrain should be prepared: consider taking an avalanche training course, let someone know where you’re going, and carry the proper equipment. Marshall said among other survival items, that includes a transceiver for tracking, a probe to find someone buried in the snow, and a shovel.

For the latest updates on avalanche conditions, check the Avalanche Canada website here.