Montana’s avalanche season is off to a nasty start after the death of a North Dakota snowmobiler on Nov. 26 near Cooke City, but that doesn’t mean the snowpack won’t stabilize as the winter wears on.
“We’re a little bit hopeful,” said Mark Staples of the Gallatin National Forest Avalanche Center in Bozeman. “We’ve seen weak layers like this that have been way worse. It could go away, but we’re not talking in days, more like months.”
The snowpack could also get worse if there is cold, dry weather followed by heavy snow.
“We generally say weird weather leads to weird avalanche conditions,” Staples said.
Donnie Duane McKay, 31, of Powers Lake, North Dakota, died last Wednesday after he was caught in an avalanche on the southwest side of Henderson Mountain. McKay was an experienced rider familiar with the area and carrying avalanche rescue gear. Yet he rode on a day when the avalanche center had issued a high avalanche danger warning for the mountainous area after it collected 24 inches of snow in 36 hours.
McKay rode up a chute with a 37-degree pitch, the prime angle for avalanching, according to Staples.
“As you go steeper, especially really, really steep like you see in the ski movies, the snow is constantly sloughing,” Staples said.
On a slope less than 30 degrees, there’s not enough of an angle to perpetuate an avalanche.
The avalanche that engulfed McKay was remotely triggered, meaning a collapsing of the snowpack near the rider sent a fracture uphill to release snow from above. The avalanche broke about 2 to 3 feet deep, 300 feet wide and bowled downhill about 400 feet, burying McKay in 5 feet of snow.
“One of the hardest things for us to teach is the collapsing of the weak layer,” Staples said. “It’s hard because it’s invisible, you don’t see it.”
The fractures can speed uphill at 100 mph to release snow that can then rumble downhill at speeds of 50 to 60 mph. A similar situation last winter killed a Bozeman rider on New Year’s Day in Gallatin Canyon. The man was one of two snowmobilers killed in avalanches in southwestern Montana last year.
Montana has the highest rate of snowmobile avalanche fatalities in the nation over the past 10 years. It ranks second for all avalanche fatalities behind Colorado.
Although McKay was facing downhill behind his snowmobile when found, it’s unclear if he tried to outrun the avalanche even though he was wearing an avalanche airbag. Carried in a backpack, an airbag, if deployed, allows the wearer to float closer to the top of the snowpack during an avalanche.
McKay’s fellow rider, who was stopped below and did not see the avalanche, found his friend within about 20 minutes but he had already died from his injuries. Statistics show that about 90 percent of avalanche victims recovered within 15 minutes survive.
Considering that there were 80 avalanche incidents in southwest Montana last year with 23 people caught, five partial burials, five full burials and four injuries, the death toll could have been much worse.
Last year’s snowpack was unstable thanks to a below-zero week in December that created large snow crystals that were then buried under more and more snow. The large crystals were like marbles waiting to roll. This year’s cold weather hasn’t produced crystals quite as large, but that can change over time.
“The snowpack is exactly like a river or pond that you see steaming on a cold morning when you get all of that frost on the trees,” Staples explained. “That’s what’s going on in the snowpack.”
The temperature at the ground is always 32 degrees. The ground is steaming like a river or lake under the blanket of snow, which is 70 percent to 80 percent air. As the steam rises through the snowpack, the snow crystals can change.
“Sometimes the snowpack can change for the good, and that’s what we’re hoping to see,” Staples said.