2021/02/06 - Montana - Wounded Buck Creek, northwest of Wildcat Lake

Published 2021/03/27 by Blase Reardon - Flathead Avalanche Center

On Jan. 13, an atmospheric river event ended with rain and above freezing temperatures to the  crest of the Swan Range. The wet snow rapidly refroze, leaving a pencil- to knife-hard crust or  ice layer (depending on location) at the snow surface. Avalanche concerns in the subsequent  three weeks centered around weak layers and slabs that developed above the Jan. 13 crust or  ice layers, because they significantly limited the potential for human-triggered avalanches on  layers deeper in the snowpack. 

Storms on Jan. 15 and 17 deposited 1.5 inches of SWE above this crust. Dry, cold weather  prevailed during the following 12 days, with Noisy Basin SNOTEL recording only 0.6 inches  more SWE by Jan 29. The height of snow at the station decreased (settled) by two inches  during this time.  

The snow above the crust weakened. Observations from Jan. 23, 25, and 26 described 15 to 20  cm of faceted snow above the crust; each also noted a layer of surface hoar capping the  faceted snow. These observations were made on the west side of the Swan Range, though the  observation on Jan. 26 was from the ridge above Wildcat Lake within a mile of the eventual  accident site. 

Wet weather returned to the region at the end of the month. It was immediately accompanied by  reports of shooting cracks, whumpfing collapses, propagating snowpack tests, and remotely and unintentionally-triggered avalanches. One of these was a near-miss, and another large slide  caught and carried a skier. The reports consistently described slabs breaking just above the  Jan. 13 crust, on weak facets or preserved surface hoar. The reported activity occurred almost  exclusively on north, northeast, and east facing slopes, in the Whitefish and Flathead zones. 

When snowfall started in earnest in the Swan Range on Feb. 2, so too did evidence of similarly  reactive slabs. That day, FAC staff remotely triggered three avalanches on northerly, mid elevation slopes. These had crowns about a foot thick and failed on preserved surface hoar  above the Jan. 13 crust and ice. The forecast team was on the east side of the range, several  drainages north of the eventual accident site. 

On Feb. 3, an observer in Noisy Basin reported extended column tests propagating with  moderate force on surface hoar six to eight inches above the Jan. 13 crust. The next day, an  FAC forecaster in the same basin observed high snowfall rates, moderate blowing snow, small  slides on test slopes, and decreasing stability through the day. Reports from elsewhere in the  region describe thickening but still reactive slabs. By Friday, Feb. 5, FAC forecasters in the  Flathead Zone were observing remotely-triggered and natural avalanches that were 20 inches  or more thick and very large relative to the path, all failing on northerly and easterly slopes on  preserved surface hoar above the Jan. 13 crust.

On the morning of Feb. 6, five riders left a trailhead at the Hungry Horse Dam planning to ride in  Wounded Buck Creek, on the east side of the Swan Range. They had decided on the  destination at breakfast that morning, after discussing the avalanche forecast. All were carrying  a full set of avalanche rescue gear (beacon, shovel, and probe) and at least two riders (Riders 1  and 4) had avalanche airbag packs. The group conducted a transceiver check before leaving  the trailhead. While all of the group had ridden with Rider 1 previously, not all of the group had  ridden with each other prior to Feb. 6. 

The ride up Wounded Buck Creek travels through the runouts of numerous large avalanche  paths with mid-elevation start zones that face southeast or northwest. The group did not see  much evidence of avalanche activity, even on slopes where Rider 1 had previously seen  avalanches. It was snowing, however, preventing a complete survey of the surrounding terrain. 

Rider 4 thought the plan was to play in the trees because of the avalanche danger. At some  point, the plan changed to riding a loop. It would entail climbing to the ridge overlooking Wildcat  Lake, then heading north to Strawberry Lake and out a drainage further north. Rider 1 had done  some version of this loop many times before. 

The climb out of Wounded Buck Creek starts at about 4300 feet. For the next 1.2 miles, the  slopes are sheltered, treed, and less than 30 degrees, though there are steep, open slopes on  climbers’ right. At about 5300 feet, the route steepens. It turns right up a tributary stream on a  treed rib below a very steep, open slope that generally faces northeast. The ground cover on  this slope consists of talus and scree, much of it fallen from a cliff at the top. The slope is over  2000 feet wide. At the south end of the slope, riders can gain a saddle above Wildcat Lake via a  steep, north-facing slope. This slope is roughly 250 vertical feet high, with a short section where  the slope angle is over 35 degrees.  

The five riders climbed to below this exit and parked at about 6000 feet elevation on the treed  rib below the steep, open slope. They were about 200 yards below the exit climb. Rider 1 went  ahead. The parked riders did not have a clear line of sight to him because of trees. 

At about 1300, an avalanche hit the group with little warning. Rider 4 reported having no idea it  was coming until it was about 20 yards away. The slide knocked all four riders off their parked  snowmobiles.

Rider 4 reported that none of the four parked riders were trapped in the snow. Their machines,  however, were tipped over or partially buried and had to be dug out. The group got no response  from Rider 1 when attempting to contact him via radio. They didn’t go look for him on foot  because it seemed slower than getting their snowmobiles unstuck.  

Rider 2’s sled was the first to be freed, and he rode up to look for Rider 1. Though he started a  transceiver search, he saw part of Rider 1’s airbag at the surface. Rider 3 soon followed, then  Rider 4. 

Rider 2 reportedly found Rider 1 against a tree, with his airbag partially deployed. His face was  below the snow surface. He was not responsive. An attempt to resuscitate him failed. It’s not  clear whether the airbag was damaged did not have time to fully inflate. 

The survivors moved Rider 1 off the slope and down to where they had been parked, where he  it would be easier to retrieve him by helicopter. They flagged the site and flagged trees on either  side of Rider 1’s snowmobile, which was buried to the handlebars. They rode back to the  trailhead and alerted 911 at 15:23.  

The Flathead County Sheriff’s Department alerted Search and Rescue teams, then decided to  wait for safer conditions to recover the victim. At 09:30 on Sunday, Feb. 7, Two Bear Air was  able to retrieve the victim via helicopter.

Each fatal avalanche accident we investigate is tragic. We do our best to describe the events to  help the people involved and the community as a whole better understand factors that may have  contributed to the outcome. We offer these comments in the hope that it will help people avoid  future avalanche accidents. 

This report is based on limited information. Rescuers did not reach the accident site the day of  the accident, and the following day, when they recovered the victim via helicopter, visibility was  poor and flying conditions were difficult, so they did not get any videos or images of the site.  Due to concerns about the avalanche hazard, FAC staff did not investigate the site immediately  after the accident. FAC staff did visit the site on March 8, although subsequent storms had  obscured the crown, debris, and most other evidence of the slide. Interviews with Flathead  County Sherriff’s Department and one of the survivors were instrumental in compiling this  report. 

This accident involved a party of experienced and expert riders who had discussed the  avalanche forecast, carried avalanche rescue gear, and had a plan to ride in what they thought  was safe terrain. It appears they changed their plan while riding. In the terrain where the danger  was most acute, they used travel practices that limited their exposure and the consequences of  a person getting caught in a slide. They may not have recognized unusually dangerous  conditions or anticipated the extent and sensitivity of avalanches likely that day. 

In northwest Montana, High (Level 4) avalanche danger is often associated with the arrival of  powerful storms and difficult travel conditions. In this case, the avalanche danger was rising  steadily with incremental loading of the weak layers buried in late January. People reported  reactive slabs above these weak layers almost immediately after they were buried. The size of  the triggered slabs grew each day during the first week in February; by Friday, February 5, the  slabs had thickened from several inches to several feet and were breaking the full width of start  zones, often with remote triggers. However, natural avalanches were isolated. Travel conditions  remained excellent in the storm snow accumulating above the January 13 melt-freeze crust,  allowing riders to travel extensively below 6000 feet with few signs of instability. Above that  elevation, particularly on slopes that faced north to northeast to east, steep slopes were primed  to avalanche.  

That scenario likely existed in Wounded Buck Creek on February 6. The party’s route prior to  the accident passed through the runouts of some avalanche paths but not through or near start  zones. The slope that avalanched on February 6 was likely the first start zone that threatened the February 6 party. Avalanche activity on similar slopes the week prior suggests that the  triggered slab was likely two feet thick on average and released on the surface hoar and faceted  snow buried in late January. It appears Rider 1 triggered the slab from below, as he approached  the steepest part of the exit slope.  

One rider in the party remarked that it was surprising how far the crown extended. Indeed, the  fracture would have propagated at least 1600 feet in order for the debris to hit the other 

members of the party parked on the treed rib. Because the open slope extends another 1000  feet to the north, the potential for an even wider release exists. A less likely scenario is that  more than one avalanche released simultaneously, and it was debris from a sympathetic slide  that hit the parked riders in the group. In either case, it appears the group believed they were  parked in a spot safe from overhead hazards.  

Carrying a full set of avalanche rescue gear allows a group the best chance of a successful  companion rescue. Supplementing this gear with airbags can reduce the chances of being fully  buried. Airbags don’t, however, protect a rider caught in a moving avalanche from trauma. Rider  1’s airbag was reportedly deflated when the other riders reached him. Two scenarios may  account for that. Either the airbag did not have time to fully deploy, or it was damaged while  Rider 1 was carried in the debris or. Accounts indicate Rider 1 was partially buried – critical; that  is, his airway was below the snow surface.  

Although we will never know if the outcome would have been different had Rider 1’s airbag  remained inflated or the survivors been able to come to his aid immediately, we do know that  companion rescue can be quickest when a party can keep a rider in view from a spot safe from  avalanches running down from above. This practice narrows the search area, limits the number  of people caught in a slide, and allows a victim’s companions to start searching immediately. It  is important to select viewpoints based on the terrain rather than past experience. In this case,  Rider 1’s ascent was obscured by snow, trees, and the distance to the remaining members of  the party, who were exposed to the steep slope above them. It is fortunate that more riders were  not buried in this avalanche.