FORT COLLINS - Avalanches that killed three people in the last week have been some of the largest reported slides in Colorado in the past 20 years, experts say.
The avalanche that killed a pair of skiers from Wisconsin Saturday near Leadville registered at least a 3.5 on an intensity scale that goes up to 5, the Colorado Avalanche Information Center said.
"We've seen a bunch of avalanches between Independence Pass and Loveland pass in the last week that have pulled out mature timber, some of it large and 50 to 100 or 200 years old in places, said Ethan Greene, director of the Colorado Avalanche Information Center. "That just shows the power and size of these recent slides."
Storms last week dumped 4 to 7 feet of snow in some parts of Colorado's mountains, leaving many backcountry areas in an "historic avalanche cycle," Greene said. The slides have been described by CAIC forecasters as some of the largest observed since the early 1990s.
The Feb. 10 fatal avalanche near Kebler Pass that killed one snowmobiler was estimated at 600 feet wide, running 750 vertical feet. Debris at the bottom of the slide piled up as deep as 20 feet.
The CAIC issued avalanche danger warnings throughout the weekend across the state. The advisory warned backcountry travelers of "unusual conditions" in the Rocky Mountains due to the heavy layer of of new snow falling atop the weak layers beneath the surface of the snowpack. Strong winds and rapid warming over the weekend were major factors, too.
"We are seeing very dangerous avalanche conditions developing from basically the New Mexico border north to Wyoming," the center said in the advisory that expired Monday evening.. "And the problem list is about as complicated as it can get. We are seeing very large avalanches taking out very old trees, mine buildings that have been around for many decades and avalanches burying roadways with 20 feet of debris."
The avalanche danger for Tuesday and Wednesday is rated at Considerable (Level 3 of 5) in the Front Range Zone and Moderate (Level 2) in the Steamboat and Flat Tops region.
"As the avalanche danger slowly trends down to the Moderate category, do not let your guard down," said CAIC forecaster Scott Toepfer. "Triggering a slide is becoming less likely, but it remains possible and the resulting avalanche could be very large. Conservative route finding is really the only method to minimize this low probability, but high consequence risk."
Greene emphasized if you are going to ski the backcountry, check the CAIC forecast before leaving, carry proper equipment and receive proper avalanche awareness training.