Avy danger down, but slide potential still exists
March 13, 2012
Avalanche danger reduced to moderate on all aspects at all elevations late last week, as spring-like, mild weather spread across the Colorado Avalanche Information Center’s (CAIC) Vail and Summit County Zone.
Though the upper layers of snowpack are consolidating and strengthening, lower layers and shaded slopes are still unsteady, CAIC forecasters say. Wind slabs are still a danger, as well, on steeper slopes.
As the snow consolidates with warmer temperatures, the thawing cycle can cause trouble for backcountry users by way of wet loose avalanches and falling cornices on sun-exposed slopes.
“If you trigger small avalanches, they may step down into deeper weak layers and release large and destructive persistent slabs,” forecaster Tim Brown wrote in a report.
Forecaster Spencer Logan called the larger slides potentially destructive.
“Approach terrain steeper than 35 degrees with caution,” he said.
Some human-triggered hard slab slides occurred during the weekend, like the one in the north fork of the Swan River in Breckenridge.
According to the avalanche report, it was triggered on the south-facing side of the ridge that encompasses the north fork bowl.
“Slide was triggered on the third run,” observer Brian Montgomery wrote. “Appeared to be triggered from the bottom of pitch. Rider outran the slide.”
The same day, Saturday, springlike avalanche activity was observed in Ten Mile Canyon, where what appeared to be a wet slide triggered, presumably from afternoon heating.
“Debris filled the bottom of the track gully but did not reach the bike path,” observer Dan Moroz said. According to his report, the slide path doubles as a popular ice climb in the canyon – Triple Tier ice climb.
On Sunday in the Gore Range, snowmobilers reported an avalanche along Elliot Ridge. According to the report, the avalanche slid from a depth hoar layer. It had an average crown of nearly 12 feet and maximum crown of 15 feet. The avalanche was about 1,300 feet wide and slid about 600 feet vertical.
“Lingering deep instabilities persist as evidenced by some human-triggered hard slab slides over the weekend,” CAIC forecaster John Snook said. “It is getting harder to trigger an avalanche, but if you find the right (wrong!) spot, you could trigger a large and dangerous slide.”