Wednesday, December 22, 2010

Staying safe in the backcountry

Avalanche danger climbs after weekend storms


By KATHERINE WUTZ
Express Staff Writer

The recent dumping of nearly a foot and a half of snow over the weekend may have given valley residents powder fever, but it caused the avalanche danger to skyrocket as well.

The avalanche danger as evaluated by the Sawtooth Avalanche Center climbed to considerable for the first time this season, thanks to what avalanche forecaster Simon Trautman called a heavy snowload and sustained winds on a weak layer of snow.

"If you're out playing on the mountains, you're vulnerable," avalanche forecaster Blase Reardon said during an avalanche safety class earlier this month.

The center formed the class to educate backcountry recreationists on how to stay safe in the backcountry.

Most large avalanches in the area are slab avalanches, in which a large "plate" of snow resting on a weak layer of snow is disturbed and shatters, plummeting downhill and sweeping away everything in its path—including skiers.

Reardon said debris in these slides has been clocked at upwards of 100 miles per hour, and avalanches can carry recreationists just as fast.

"Anything you hit, you're going to hit hard," Reardon said. "There are a lot of trees and rocks out there.'

A major problem for avalanche victims is "terrain traps" such as stands of trees.

"This is the equivalent of a bread slicer in the backcountry," Reardon said, pointing to a picture of a stand of subalpine fir. "This is not something you want to be pushed through."

He said recreationists should be on the lookout for signs of instability. Cracking, collapsing and "whumping" noises are all signs of a slab over a persistent weak layer that is on the verge of sliding.

Avalanches typically occur on slopes steeper than 30 degrees, and the chances of slides can be increased by factors such as recent heavy snowfall or rain, rapidly increasing temperatures or strong winds that transport snow.

Reardon said heavy precipitation is more than one inch of snow or rain per hour. In last weekend's storm, precipitation rates reached almost two inches per hour in some areas, and the center reported small natural avalanches from the northern Sawtooths to the southern Wood River Valley, including a few small slides along state Highway 75 near Boxcar Bend.

The best way to prevent becoming an avalanche victim is via proper trip planning, said center Director Chris Lundy. Lundy urges recreationists to always have a backup plan in case their planned trip to the backcountry is affected by dangerous avalanche conditions.

"People get in accidents because they don't have a plan B," he said.

Without a backup, Lundy said, skiers or snowboarders are more likely to venture into terrain they know is risky. If the center's advisory calls for a high danger in the area in question, however, there may not be a safer option.

"That's a good time to stay home and watch TV," Lundy said with a laugh.

He also urged conducting stability tests using pits and hand shears, and watching for any sign that the snowpack is unstable.

"You have to pay attention to that one clue," he said. "It might be the only one you get."

The center will conduct a basic avalanche class on Tuesday, Jan. 4, from 6-9 p.m. at the Community Campus in Hailey. The class is free but a $5 donation is appreciated.

Katherine Wutz: kwutz@mtexpress.com




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