Three exceptionally large avalanches were triggered earlier this week inside gate-accessed terrain at Mt. Hood Meadows, prompting the resort to close entry to the popular Heather Canyon.

Resort authorities used artillery to trigger two of the slides Tuesday and the third Wednesday. Such measures are taken so avalanches don’t release naturally when skiers are around and so skiers don’t cause the slides themselves.

Heavy falls of rain and snow created conditions for the slides, said resort spokesman Dave Tragethon. The resort reports getting 14 inches of snow in the past 48 hours.

Meadows sees slides of this magnitude maybe two to three times every couple of years, Tragethon said. He said they would likely occur more often if the resort didn’t perform ongoing avalanche control work, which regularly produces small slides.

The crown of the avalanche that slid Wednesday was estimated to be 20 feet deep. Tragethon didn’t know the specific size of the two slides that occurred the day before.

Avalanche debris is piled 30 feet high in spots, and the resort won’t be able to open Heather Canyon until workers can clear egress for skiers and snowboarders. It will be closed through at least the weekend.

The canyon, which is home to some of the resort’s most rugged terrain, can be accessed through gates that are open or closed daily, depending on conditions.

Meadows remains open, and skiers can safely ski elsewhere in the resort.

The slides originated in the resort’s Super Bowl and upper Clark Canyon, as well as an area Meadows referred to as “the Basalts,” which is above the resort’s A-Zone.

Very dangerous backcountry avalanche conditions were present above and near treeline Tuesday, as well as above treeline Wednesday. The Northwest Avalanche Center expects backcountry avalanche danger to remain high above treeline — and considerable near and below treeline — Friday.

That outlook doesn’t apply to ski areas such as Meadows.

-- Jim Ryan; jryan@oregonian.com; 503-221-8005; @Jimryan015

Visit subscription.oregonlive.com/newsletters to get Oregonian/OregonLive journalism delivered to your email inbox.