Snowpack still unstable in Summit, Vail zone
March 5, 2012
New snow and wind over the last week has increased avalanche danger, though danger ratings haven’t been elevated, Colorado Avalanche Information Center officials say.
Danger remains considerable at all elevations on all but primarily west-facing slopes, though it’s creeping toward the higher end of considerable danger. Danger is moderate on west-facing aspects at all elevations.
“Wind slabs and persistent slabs remain the biggest avalanche problems,” Colorado Avalanche Information Center (CAIC) director Ethan Greene wrote in his Monday morning Vail and Summit zone report. “Wet-loose avalanches could also be an issue today on south through west slopes. Remember that small avalanches are good triggers for large avalanches.”
Avalanches were triggered with explosives Monday morning on south, southeast and east aspects of Loveland Pass. They were 3-6 feet deep, 70-150 feet wide and ran up to 500 feet vertically.
“It’s getting harder to trigger avalanches, but many of the recent avalanches have been both large and destructive,” Greene said.
As temperatures change and wind has its effects on recent snowfall, snowpack behaves differently, sometimes becoming more stable and sometimes becoming less so.
According to Greene, the 1-2 feet of new snow in the Vail and Summit zone stabilized somewhat with warming temperatures. However, a variety of problems remain, he said, such as wind slabs, persistent slabs and wet-loose avalanches.
Recent avalanche observations include a soft-slab avalanche on a southeast facing slope near treeline on Vail Pass, triggered by a snowmobiler. Several natural avalanches – 3-5 feet deep and nearly 500 feet wide – slid south of Breckenridge on south and southeast, above-treeline slopes.
Crews near Fremont Pass triggered an avalanche 3-feet deep and 200-feet wide with explosives on a northeast-facing slope above treeline. A natural avalanche on the east side of Peak 6 was 4 feet deep and 450 feet wide.
Regardless of whether the latest snowfall is consolidating well, the snowpack as a whole is resting on a weak foundation of facets and depth hoar, which in some cases can be rather large layers.
Middle snowpack layers are gaining strength, making it harder to affect deeper weak layers directly, but it can still happen, Greene warned.
“This snowpack requires respect,” he said said. “Approach steep terrain conservatively. You need to be very careful in your route and terrain selection today.”