Avalanche danger surges
March 1, 2010
BOULDER, Colo. – Backcountry enthusiasts beware: Recent storms have piled snow on a weak snowpack, creating perilous conditions on many mountain slopes. More than 500 slides have been recorded in the past week alone, according to the Colorado Avalanche Information Center.
Heavy precipitation over a short time frame across the southern portion of the Front Range zone (which includes much of Grand County) has increased the avalanche danger to HIGH. Natural avalanche activity closed Highway 40 over Berthoud Pass last night. Snowfall rates of 2-4 inches per hour stressed a weak underlying snowpack.
With the typically snowy month of March ahead, forecasters with the CAIC are warning skiers, snowmobilers and all backcountry users that avalanche danger remains “considerable,” with conditions ripe for more big, damaging slides in the coming week.
“The last 10 days have been one of the most active periods we’ve seen in years,” said CAIC director Ethan Greene. “Avalanches have been breaking deeper, sometimes carrying the entire year’s snowpack with them. We’ve seen some very big and destructive slides.”
So far this season, avalanches have claimed three lives in Colorado, including a backcountry skier who was caught by a slide near Aspen on Feb. 23. Despite being with a group other skiers, the victim did not have an avalanche beacon and was not recovered in time.
Greene said the current conditions have resulted from a large storm that dropped between 20 and 50 inches of snow on the high country between Feb. 18 and Feb. 22. The new snows fell on a snowpack that had weak layers which formed in January and a very weak layer at the base from October. Strong winds on Feb. 21 and 22 build large slabs on top of the weak layers.
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The wind and weather set the stage for a particularly active avalanche cycle statewide, with significant activity in the Aspen, Vail/Summit County and San Juan zones. More than 500 slides, some hundreds of feet wide, have been reported. Greene said hundreds of additional slides may have gone undocumented. At least seven people have been caught in slides during this period.
With new slabs on top of unstable layers, conditions are right for avalanches to break in the middle of pack or near ground, Greene said.
“What worries me is that we have seen more people involved in avalanches this year than the past five years,” he said. “We’ve had three fatalities and we’re only halfway through the season. And it could get worse. Snow conditions are as tricky and as dangerous as I’ve seen within the last several years.”
CAIC forecasts rate avalanche danger on a scale ranging from low probability to extreme. Currently, avalanche danger is rated “considerable” for all of the high country except for the Grand Mesa. However, most fatal avalanches in the US occur when danger is “considerable.” That’s because conditions that make human-triggered slides likely are not always obvious.
The CAIC urges anyone planning to travel in the backcountry to get the most current avalanche conditions by visiting: http://www.colorado.gov/avalanche. CAIC forecasts backcountry avalanche and mountain weather conditions for 10 Zones in the mountains of Colorado. Backcountry Weather forecasts are issued twice daily, at 6:00 am and 1:00 pm.
The CAIC also offers a Twitter feed to provide up-to-the-minute reports on conditions and slides. Sign up to catch their tweets at: http://avalanche.state.co.us/pub/follow.php
CAIC also asks backcountry travelers to report on conditions that they experience. Observations can be reported to firstname.lastname@example.org or (303) 499-9650.
As always, backcountry travelers are strongly advised to travel in groups, to carry appropriate avalanche safety equipment, including a shovel, probe pole, and avalanche rescue beacon. Backcountry enthusiasts should not only be carrying this equipment, but know how to use it.
The Colorado Avalanche Information Center, a program of the Colorado Geological Survey, is the oldest and one of the most respected public avalanche forecast programs in the United States. The CAIC provides avalanche forecasts for all of the state’s mountain ranges to the Colorado Department of Transportation and to backcountry users.