Wednesday, December 24, 2008

Heavy snows bring high avalanche risk

More snow expected later this week

Express Staff Writer

Heavy snowfall dumped across the mountains of central Idaho in the past week has made traversing the backcountry a high-risk proposition.

Both on out-of-bounds areas off the backside of Baldy and in the mid to upper elevations in surrounding ranges, backcountry skiers, boarders and snowmobilers are advised to exercise extreme caution due to a serious avalanche threat. On Tuesday, the Sawtooth National Forest Avalanche Center in Ketchum assessed the avalanche risk as "considerable."

According to avalanche forecaster Chris Lundy, anywhere the snow is deep enough to ski or ride, the snowpack consists of sugary facets buried 1.5 to 2 feet deep. He said Sunday night's storm added significant weight to a snowpack that has very little strength, resulting in unstable conditions on many mid- to upper-elevation slopes.

"We observed significant signs of instability yesterday, including triggered avalanches and collapsing and cracking of the snowpack, and I would expect these to continue today," he said.

While the recent storm wasn't enough to fully tip the balance of the local area's weak snowpack, it did make for some spicy conditions in the backcountry that the avalanche forecasters themselves witnessed, Lundy said.

"By stomping around near the top of Timber Bowl on the backside of Titus Ridge, we released a small slab about 40 feet wide and breaking about 1.5 feet deep," he said. "On the other side of the ridge above Titus Lake, we triggered another, larger avalanche—this time about 100 feet wide and 1 to 2 feet deep."

Lundy said the slide initiated in steep rocks near the ridgeline, but swept down into lower slope angles. He said a group near the Cross—a popular backcountry destination on the east side of Galena Summit—triggered a small slide from a good distance away, experienced numerous collapses and reported poor stability.

Janet Kellam, the avalanche center's lead forecaster, said the primary danger areas and the sites of instability seen by the forecasters are places that had a snowpack before the last round of storms. She said the main areas to watch out for are on west, north and east-facing aspects.

There have already been three avalanche fatalities in the West this year, two in Colorado and one in Utah. There have also been quite a few close calls and injuries from slides, Kellam said.

She advised that for now, it's best to be cautious and check the daily avalanche advisories as more snow continues to drop this week. The National Weather Service was predicting the arrival of another winter storm sometime later today or early Thursday, which should continue to add to the local snowpack.

Up to 10 inches of snow is expected to fall in the mountainous areas of south-central Idaho as part of the strong Pacific storm.

Kellam said that in the long term, the deepening snow depths will reduce the slide hazard. She said that though the weight of the new snow will initially increase the risk, it will eventually help make snowpacks more uniform.

"Conditions will stabilize," she said.

Daily avalanche advisories from the Sawtooth National Forest Avalanche Center can be accessed by logging on to and clicking on the Sun Valley button on the map.

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