Wet snowstorm elevates avalanche threat
Buried wind slabs and crusts complicate snowpack
April 7, 2010
Steamboat Springs — The heavy snowstorm that dumped 21 inches of snow on the summit of Steamboat Ski Area in 48 hours Monday and Tuesday has prompted the Colorado Avalanche Information Center to issue a strong caution to backcountry skiers headed for powder skiing beyond the ski area's boundary.
As of 5:30 a.m. Wednesday, CAIC rated the backcountry avalanche danger high on all slopes at all elevations.
"Automated weather stations indicate an average of 18 inches of new snow falling in a period of less than 12 hours" near Steamboat Springs, CAIC avalanche forecaster John Snook wrote in an online report. "Close to 2 inches of snow water content added a lot of weight to the snowpack in a short time span."
Natural and human-triggered slides were likely Wednesday, he added.
"A lot of stress (was) added to the snowpack in a short time span. The snowpack will need time to adjust," Snook wrote. "Backcountry users need to allow some time for the snowpack to adjust to the new snow load by staying clear of all terrain steeper than 30 degrees through the warning period. Recent avalanche activity is one adjustment process that you should not be a part of."
The rate at which the snow accumulated was notable in the northern part of Routt County. Weather observer Art Judson said the 9 inches recorded at his measuring station between downtown Steamboat and the ski mountain represented the biggest 24-hour snow total in the city this winter. In most winters, a 9-inch snowfall would not be remarkable.
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Farther north, he said, an automated snow measuring site at Steamboat Lake indicated that 19.4 inches had fallen in the eight hours between 6 p.m. Tuesday and 2 a.m. Wednesday. At one point, the site recorded 6.3 inches of snowfall in an hour, Judson said.
On the Colorado/Wyoming line in Whiskey Park, 17 inches of snow fell in six hours Tuesday.
Closer to Steamboat, at the foot of Buffalo Pass, the Dry Lake measuring site recorded 15 inches of snow in 17 hours. Hybrid snowmobile skiers headed for Buffalo Pass this weekend might consider that, based on a report from late Tuesday afternoon, none of the familiar roads packed by snowcats was visible.
Snook said an expected return to higher temperatures later in the week could accelerate the consolidation of the snowpack. But in the near term, gusty conditions have created hard wind slabs and cornices. Those slabs combined with buried melt-freeze crusts have produced slick surfaces that can allow avalanches to run "fast and far."
"Warmer temperatures and sunshine are back in the forecast for the remainder of the week. You need to be thinking winter today, but the snowpack will quickly transition into spring on Thursday," Snook said Wednesday. "Expect to find an increase in wet slide activity as the week progresses."
— To reach Tom Ross, call 871-4205 or e-mail email@example.com