Deadly Winter - A Look At A Yearlong Avalanche Cycle In Montana

By | November 13th, 2012

The Barrels in MontanaThe prevailing southwesterly winds begin to load The Barrels during the 2011-'12 winter in Montana.

Words and photos by Pat Clayton

Standing at the bottom, eyes gazing upward, mouth position - donut hole. It was the state many of us found ourselves in more than once during the 2011-12 winter, as the snowpack around southwest Montana seemed to be in the valley floor rather than on the mountainsides. An impressive display of anger from an utterly upside-down snowpack, like wet scabs, these deep slabs slipped off their precarious perches roaring again and again to the end of their historical run outs. The Gallatin National Forest Avalanche Center did yeoman's work to inform the public that this was no ordinary snowpack, while the Bridger Bowl Ski Patrol worked it hard to keep the mountain safe. 

Forest service avalanche scientist Karl Birkeland summed it up this way:

“The 2011-12 season started with a thin snowpack. In fact, in the Bridger Range the snowpack was less than two feet deep for more than two and a half months. This resulted in an extremely weak base that was loaded up by snowfall in February and March. The big excitement came as we shifted from dry-snow to wet-snow avalanches toward the end of March. Warm weather saturated the snowpack with melt water, and then a storm dropped almost two inches of snow water equivalent. This set the stage for numerous full depth wet slab avalanches both inside and outside the ski area. The ski area did an excellent job of managing the hazard and keeping people out of the way of these monster slides.”

Eric Knoff, full time forecaster for the Gallatin National Forest Avalanche Center adds:

“During 2011-12 season, the GNFAC saw the second highest number of avalanche incidents in its 22 years of operation. A total of 51 incidents were reported throughout the season, three resulting in fatalities. This number represents southwest Montana; the total number of avalanche incidents throughout the state was much higher. In fact, Montana (tied with Colorado) had the highest number of fatalities out of any state in the nation with seven fatalities. This high number of incidents can be directly attributed to a shallow and weak snowpack that plagued our area the entire winter. Early season snow followed by prolonged periods of cold, dry weather formed a thick layer of depth hoar near the ground. This layer remained weak throughout the season, producing avalanches from November to April. Whether it was half-mile long crowns in Teepee Basin or unprecedented wet slabs in the Bridgers, the season of 2011-2012 was one to remember."

Bridger Bowl avalancheThe first one, it peeked through the clouds one morning. A shallow snowpack and a 1- to 3-foot fracture. The instability clearly evident on the ground, the canary in the mine to what would end up an impressive yearlong avalanche cycle.

Mundys BowlPatrol worked this one loose in Mundy's bowl.

Bridger PeakBridger Peak went as well, it was nearly a mile long fracture, wrapping around to the unseen south face as well. Photo: Richard Griffen.

Saddle at Bridger BowlSaddle went fairly early, triggering off it's wind loaded northeast shoulder along the sugary rock band.

Deeper Slabs at BridgerMore snow resulted in deeper slabs, the ground rot neither crushed nor flushed.

Pat's Cryptic Photo
football fieldJust beyond the boundaries, the football field erases many tracks.

Bridger Bowl Ski PatrolPatrol working it hard to keep the in bounds safe.

Deep Hard SlabDeep hard slab. This one was skied on thousands of times before an overnight load tipped the scales.

An Impressive Crown LineErik Knoff investigating an impressive crown line. Lucky high marker. Photo: GNFAC

South Saddle avalancheSouth saddle was kind on this day. Photo: T Thesing

Doug Chabot Doug Chabot displaying what the areas snow pits were showing. He pulled that 6-foot column out in one piece, all of it sitting on sugar.

B gully avalancheThe morning it all came down. B gully to the ground.

Another Bridger Bowl avalanche

Powerful slides filled numerous gulliesPowerful slides filled numerous gullies. Photo: GNAFC

Morning Glory Uncorked
Bridger Bowl Ski PatrolA dicey situation managed expertly by the patrol.

Inbounds Avy at Bridger BowlAn icy mogul field is rooted out by weight from above.

Early Season, this can happenEarly season is when conditions like this can form. Every season and snowpack is different. Take only what she gives and always ride it with a smile!

Thanks.

Co-snow safety director at Bridger Bowl, Richard Griffen, was on the front lines and in closing adds:

"This was the worst snowpack year in my 17 years patrolling Bridger Bowl. Some years you just say, 'No - it isn't worth it.' If basic knowledge states signs of local activity, stay off avalanche terrain. Honor the storm; respect the mountains, live to ski another year."

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