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Avalanche debris dwarfs motorists on Highway 22 below Glory Bowl near Teton Pass on Friday afternoon. WYDOT avalanche control operations and cleanup kept the pass closed for much of Friday. BRADLY J. BONER / JACKSON HOLE DAILY

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Epic avalanche danger had highway crews and ski patrollers walking on eggshells Christmas and Boxing Day as they sought to protect roads and ski runs from the danger brought by a massive holiday storm.

Falling at a rate of 3 inches an hour, 30 inches of snow piled up on Rendezvous Mountain and the Tetons, raising the slide danger to extreme. At the Jackson Hole Mountain Resort, a “sizeable slab avalanche” Christmas morning caught a ski patroller who survived uninjured, the Bridger-Teton National Forest Avalanche Center reported.

Highway workers closed Teton Pass between Wilson and Victor, Idaho, at 4:30 p.m. on Christmas, and natural avalanches hit the road soon thereafter. Forecasters at the avalanche center recommended against travel in avalanche terrain, saying avalanches were certain on some slopes.

The growing danger on Christmas began to become obvious to workers, said Ed Smith, maintenance foreman for the Wyoming Transportation Department.

“Things were starting to move up there,” he said of conditions on Teton Pass. “There was 20 inches or more at our study plot,” halfway up the mountain at Phillips Bench, he said.

Glory Slide released naturally sometime after the closure and hit the road, Smith said. Just south of Jackson the Gravel Pit Slide released and filled up a roadside pit, but debris on U.S. 191 were easily cleared by snowplows, he said.

Boxing Day morning highway crews got a taste of what lay lurking when they remotely activated an Avalanche Guard on the edge of Glory Bowl and launched an explosive charge into the notorious slide path above Wyoming Highway 22. When it exploded, the resulting avalanche buried the highway under 20 to 25 feet of snow.

“That’s about the biggest slide I’ve seen up there in 20 years,” Smith said.

The highway team also used set of Gaz-Ex exploders in Glory Bowl and in Twin Slide. An avalanche on the latter ran to the highway, too, and buried it under about 12 feet of snow. Broken branches in the debris indicated the slide chewed up a tree along the way.

After that excitement, all that was left to do was plow through the avalanche debris under the slide paths and remove the knee-deep snow on the rest of the highway, Smith said. That lasted into the afternoon.

The crown, or starting face, of the avalanches ranged up to 5 feet deep, the avalanche center reported Friday. Forecasters and patrollers also told of “sizeable loose snow sloughs” that were triggered by skiers and simple snow accumulation.

“These sloughs entrained large volumes of snow and ran fast and far,” the avalanche center reported. “Some occurred on relatively low angle slopes.”

The center’s updated daily report is available at www.jhavalanche.org. Forecasters extended their avalanche warning to 11 p.m. on Friday and said it covered the Teton, Snake River, Salt River and Wyoming ranges.

The storm prevented the opening of the new Jackson Hole Aerial Tram on Christmas and the day after. Skiers who were able to ride the Bridger Gondola after delayed morning openings said they were directed away from the south side of the resort to gentler terrain.

Some roads in the valley were nightmarish, especially on Christmas. START bus drivers were challenged to make it into some bus stops because of deep snow or slippery roads.

Avalanche scientists are worried that one of a number of November rain crusts deep in the snowpack will keep the slide danger elevated.

The storm will be good for ski resorts as it pushed the snowpack depth at the middle of Rendezvous Mountain to 138 inches. Grand Targhee reported 71 inches of snowpack and Snow King had almost 3 feet at its base.