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'Gigantic' avalanche closes Heather Canyon at Meadows

March 16, 2011

"Heather Canyon is closed due to a gigantic avalanche," read a hand-written sign at the bottom of the Hood River Express chairlift Friday afternoon.

Gigantic is right.

In early morning operations the day before, Mt. Hood Meadows ski patrol triggered a massive avalanche that swept down the Clark Canyon side of the ski area's most remote terrain and pretty well inundated everything in its path.

"We continue to assess the situation daily," Dave Tragethon, MHM marketing and communications director, said about the area closure. "There's a lot of snow moving that's taking place right now and we have snowcats working to make it passable."

Tragethon said the resort is in the middle of another snow system and it's not yet known when the area can be reopened to the public. He also said the long-range artillery mission that caused the avalanche was a success because it occurred under controlled circumstances when the resort was closed and nobody was in the area.

"That's precisely why we carry out those types of missions," he said."

The following is a report of the incident, which occurred in the early morning hours of March 10:

Mt. Hood Meadows ski patrol conducted routine avalanche hazard reduction operations early Thursday morning in the area above Heather Canyon called Super Bowl. Low visibility meant patrollers could not see up the canyon from the base of the Howitzer cannon, which they use for long-range reduction missions, to see if the artillery impact and shockwave had triggered any large-scale slides. Once they were able to ski down to the base of the canyon, patrollers came across the remnants of a huge slide that traveled down about two miles of the mountainside, leaving a remarkable reminder of the power of nature in its wake.

In places a scour line of 15 vertical feet stood at the edge of the slide where skiers would normally access the run-out to the Heather lift; tractor-sized ice chunks lay on top of a river of snow, flowing down the canyon and coming to an end a quick walk's distance from the Hood River Meadows parking lot.

Weather cleared up the following day and allowed two patrollers safe access to the top of Super Bowl to investigate the event. Tighe Stoyanoff and Paul Klein gave a report based on what they saw.

"As the sun came up on Friday the 11th, the weather forecast held true and visibility allowed for further avalanche hazard reduction and investigation into the previous day's events.

"Patrol personnel traveled to the fracture line of the avalanche at the 9,000-foot level; very close to the top of our permit area. It was determined that the avalanche was triggered during our artillery mission on the morning of the 10th just after 6 a.m.

"The slide ran on an old buried and persistent weak layer. Average height of the fracture was 5-6 feet, with areas in excess of 12 feet. The hard slab traveled an estimated 3,900 feet of vertical and 2.5 miles as the crow flies."

The two noted that the Wy'east face, which is directly above Super Bowl, did not slide in the event. In January of last year a major slide higher up occurred and took a similar path down the canyon (and other canyons).

"It is presumed that Wy'east has the same persistent weak layer and similar loading that contributed to the slide at the 9,000-foot level in Super Bowl," they wrote. "Saturday the weather, snow pack and some grooming near the bottom of the chair allowed Heather Canyon to open for a short time. Absolute Magnitude was the only gate open, which allowed patrol to better inform guests of the debris hazards and difficulty of access to the chair. Weather closed in again just before 11 a.m., causing increased concern for the Wy'east face and resulting in the canyon's closure.

"Wy'east is outside of the Meadows permit area and receives no active avalanche hazard reduction. Historically slides originating from Wy'east face have deposited debris in the lower portions of the Clark Creek drainage.

"Pictures speak more than these words in describing the magnitude of this slide and the challenges we face with this terrain."

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