Takeaways from Last Season’s Historic Avalanche Cycle
Was last spring’s historic avalanche cycle an aberration, or a harbinger of extreme weather events to come?
At 3:45 p.m. on March 7, 2019, an enormous avalanche released high on the west side of the Tenmile Range. It roared down an existing chute—known as the Y in the pronounced “SKY” chutes above Copper Mountain—toward Highway 91. Instead of stopping at the historical end of the established avalanche path, the tsunami of snow thundered through 1,100 linear feet of dense forest, snapping or uprooting every tree in its wake before burying three vehicles on the highway—and five people inside them. One car was pushed 10 feet off the road by the snow and covered so completely that only a sliver of one of its tires was visible from the surface.
Miraculously, all five people survived with no major injuries. The avalanche was a freak and potentially unprecedented event, with no record of a slide having hit the highway before. But it was only one of thousands of massive releases that turned Colorado into the avalanche capital of the world for the first two weeks of March, after the state received up to 15 feet of wet, heavy snow and the fragile base gave way. “Seventy-four of the 117 SNOTEL (remote weather) sites in the state of Colorado recorded either their most precipitation in the month or second most”—in just the first two weeks, Brian Lazar, deputy director of the Colorado Avalanche Information Center (CAIC), said at the annual Colorado Snow and Avalanche Workshop at the Breckenridge Riverwalk Center in October.
“For everyone on staff, it was unanimous that we’ve never seen anything like this in our careers,” said Lazar, one of four experts to present about the historic March cycle at the Breck workshop. “So we started calling people who’ve been around a lot longer than us, and sure enough, they hadn’t seen anything like it either.”
Much of the early madness was centered in Summit County. On the morning of March 3, an avalanche path called Big Sam in Tenmile Canyon dusted Interstate 70. Snow from another path nearby, Monroe, crossed both eastbound lanes of I-70 at 5 p.m.—the first time measurable avalanche debris had hit the road there in 36 years. Video of the event made national news and hinted at what was to come statewide.
Two days later, an explosive-triggered slide just east of Loveland Ski Area covered I-70 with 15 feet of snow and closed the highway for 10 hours. The next night, in the middle of another intense storm, a natural avalanche on Vail Pass covered and closed the interstate again. Continued snow led the CAIC to rate the avalanche hazard in four zones “Extreme” on March 7, the first time in history. That morning, a huge avalanche mowed down the forest below Peak 1, creating a new, naturally cleared ski run above the Town of Frisco. Another, in the so-called Poop Chute below Peak 4, ruptured a gas line at Copper Mountain. A ski guide died in a slide on Jones Pass, just east of Summit, that afternoon. Then Y Chute slid, burying three cars. Amazingly, the chaos was just ramping up.
On March 8, an explosive-triggered avalanche in the Black Widow path below Arapahoe Basin deposited 20 feet of snow on US Highway 6, cutting off the ski area. In Peru Creek east of Keystone, where a slide on March 9 took out transmission lines, a weather station recorded a 38 percent increase in snow water equivalent (the amount of water in the snow) over 10 days. Two rarely seen D5 avalanches—the most destructive and the largest known size—ran in Aspen, including one that was two miles wide. After another three-day storm that focused on Southern Colorado, an avalanche obliterated the Hinsdale County sheriff’s home while the sheriff and his two daughters slept inside. Remarkably, they escaped with only minor injuries.
In all, the cycle killed two people, destroyed 10 structures, and buried 10 motorists and seven residents. How historic was it? Experts estimate it had been at least a century since a similar event occurred, though signs indicated it could have been much longer in certain zones. “Some of the trees we pulled out of debris piles in the Silverton area are over 300 years old,” says Kelly Elder, a research hydrologist with the US Forest Service, who is leading the Colorado Big Avalanche Project, a multi-agency, multiyear effort to analyze the March cycle.
Perhaps the biggest question is whether we’ll see anything like it again in our lifetimes. The heavy, maritime snow was unusual for a state where most flakes fall light and dry. Some worry that extreme avalanche cycles, like hurricanes and firestorms worldwide, could become commonplace as the atmosphere warms. “Everybody thinks this was a climate event, but in my mind this was a weather event,” Elder says. In other words: he thinks it was a one-off. But only time, and Mother Nature, will tell.