2/15/2014 – Avalanche Incident – Canyon Creek, Whitefish Range

Updated Information of Avalanche Incident in Canyon Creek – 2/15/2014

Also available as .pdf here.

Canyon Creek Avalanche Incident Report
Canyon Creek, Whitefish Range, MT
Date of Avalanche: 15 February 2014
Date of Investigation: 16 February 2014 

INCIDENT SYNOPSIS

On Saturday, February 15, 2014, a snowmobiler triggered an avalanche on a southeast facing (aspect 150 degrees) slope in the Canyon Creek drainage in the southern Whitefish Range. The slope the rider triggered the slide on is one of a series of southerly facing chutes known as the “Skook Chutes” or “Seven Sisters”. We investigated the avalanche on February 16, 2014. The avalanche failed on a layer of soft, faceted snow sitting on top of a hard, melt-freeze crust about 30 cm (13 in.) from the surface. It was approximately 275 m (900 feet) wide, ran 213 m vertical  (700 vertical feet) (from approximately 5930 feet to 5235 feet), and 387 m linear (1270 lineal feet). Avalanche debris reached and crossed the Canyon Creek Road (closed in winter and used as a groomed snowmobile trail), and was reported to be about 1.8 m (6 feet) deep on the road. We measured other debris piles not on the road at 2.5 – 4.5 feet deep. The debris reached the creek bottom below the road which is a terrain trap. The debris and bed surface were already covered by 5-20 cm (2-8 inches) of new snow overnight which made assessment slightly more difficult. 

The alpha angle (toe of debris to the crown of the avalanche) was 31.5 degrees. The average slope angle at the crown was 40 degrees. We received detailed information from an individual involved who was sitting on the Canyon Creek Road when the avalanche occurred. Four people were partially buried, and he was buried with only his right arm and head out of the debris.

The avalanche was classified: SS-AMu-D2-R4-I (This translates to a soft slab (SS) avalanche triggered unintentionally by a snowmobiler (AMu). The avalanche rates 2 out of 5 on the destructive scale (D2) which means it could bury, injure, or kill a person. It was large relative to the path (R4), and failed at the interface between the new and old snow (I).)

 

Following video courtesy of individual involved: 

 

 WEATHER AND SNOWPACK

Weather data are from the Whitefish Mountain Resort Ski Patrol Weather Log at the summit of Big Mountain in the southern Whitefish Range. These data are located about 2.8 km (1.7 miles) from the incident site. The closest SNOTEL site is Stahl Peak in the northern Whitefish Range about 60 km (37 miles) to the northwest. This site showed the average snow water equivalent to be 91% of median, and the precipitation to be 85% of average. The entire Flathead River Basin was 108% of median for snow water equivalent and 91% of average precipitation.

Beginning February 1, 2014, an arctic air mass parked itself over the region until around February 10, 2014. Prior to this a melt-freeze crust formed on sunny aspects throughout the advisory area. Small accumulations of snow occurred periodically and fell on this crust. During the cold air outbreak, the surface and near surface snow became weak and faceted causing weak layers to form on top of the melt freeze crust. The next notable precipitation commenced the afternoon of February 10, 2014 and snow accumulated incrementally through February 15, 2014 (date of incident) (Figure 1). During that arctic outbreak mountain temperatures reached below -20 °F (Figure 2). When the cold air mass exited the region, temperatures rose with new snowfall throughout the advisory area. This pattern created an upside down snowpack where heavier, dense snow fell on top of less dense, weaker snow. This new snow was accompanied by light to moderate winds according to Ski Patrol weather logs (Figure 3). On Wednesday and Thursday, February 12-13, 2014, an avalanche warning was issued for the entire advisory area with a hazard rating of HIGH.

 

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Figure 1: Snow Depth and Daily Snow at Summit (6,817 ft.), Big Mountain, Whitefish Range, from February 8, 2014 to February 15, 2014. The event took place on February 15, 2014.

 

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Figure 2: Air Temperature at Summit (6,817 ft.), Big Mountain, Whitefish Range, from February 8, 2014 to February 15, 2014. The event took place on February 15, 2014.

 

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Figure 3: Estimated Wind Speed and Direction at Summit (6,817 ft.), Big Mountain, Whitefish Range, from February 8, 2014 to February 15, 2014. The event took place on February 15, 2014.

 

Flathead Avalanche Center (FAC) staff were in nearby Kimmerly Basin and Skookoleel Creek as well as through Canyon Creek on Friday (2/14/2014) where they found unstable conditions on all aspects. They experienced collapsing, cracking, and unstable results in their Extended Column Tests (ECTs) in Kimmerly Basin. They found weak, faceted snow sitting on a crust in one of their snow pits on a southwest aspect. They observed no natural avalanches throughout the day. Temperatures steadily rose on the day of the avalanche and skies were clear and sunny until the late afternoon when clouds developed.

Unstable conditions existed throughout the region and the avalanche hazard was CONSIDERABLE in the Whitefish Range on the day of the incident. Other human triggered avalanches occurred on Saturday were reported that evening or Sunday. BNSF Avalanche Safety reported natural avalanche activity that occurred in the nearby Flathead and Lewis Ranges on Wednesday and Thursday prior to the date of this avalanche. No natural activity was reported or observed in the Whitefish Range in the days leading up to this incident. The bottom line in the avalanche advisory for that day read:
“Today, the avalanche hazard is CONSIDERABLE. This means that human triggered avalanches are likely and natural avalanches are possible. The snowpack is tender right now waiting for the right trigger. Dangerous avalanche conditions exist, and conservative decision making is essential. The advisory is a starting point, and the hazard could be higher or lower at any location which makes assessing each and every slope very important. The hazard could rise by the end of today as temperatures and snow levels rise later this afternoon. Pay attention to rapidly changing conditions.
Note: We are in a period of tricky and dangerous avalanche conditions. Very cautious backcountry travel is warranted. Since February 8, avalanches have killed six people and seriously injured three in the western United States in five separate incidents.”

 

AVALANCHE

FAC staff received a report of a snowmobile triggered avalanche on the evening of Saturday, February 15, 2014 in Canyon Creek in the Whitefish Range (Figure 4 and 5). Staff spoke with a local snowmobile rental company whose clients reported the avalanche to them. Initial reports were vague, but stated no one was seriously injured and everyone involved made it out without further incident. FAC staff visited the incident site on Sunday, February 16 (the day after the accident), and completed a fracture line profile on a southeast aspect (150 degrees) and found an approximately 30 cm (12 in.) slab sitting on a layer of faceted crystals over a 3 inch (8 cm) thick melt-freeze crust  (Figure 6 and 7). The bed surface of the avalanche was the melt-freeze crust at 30 cm (12 in.) below the surface. We were able to safely access the middle portion of the crown, but new snow and wind loading prevented a ground measurement of the width of the crown.

 

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Figure 4: Overview of avalanche site in Canyon Creek, Whitefish Range. The site is approximately 2.8 km (1.7 miles) from the summit of Whitefish Mountain Resort and designated as the white polygon.

 

 

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Figure 5: Site overview of the avalanche in Canyon Creek, Whitefish Range. Skookoleel Peak (~6840 ft.) is the named peak on the background.

 

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Figure 6: Crown profile of the avalanche with failure layer denoted with red line.

 

 

 

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Figure 7: Generalized snow profile image at the crown of the avalanche.

 

 

Stability test results on the crown showed easy force to initiate a fracture which then propagated across the column (ECTP1 Q1). We moved about 2 m to the west and performed another ECT where the slab above the weak layer was a bit thicker (55 cm), and results, again, showed easy force to initiate fracture propagation (ECTP6 Q1).

The debris ran across the Canyon Creek Road (groomed snowmobile trail). Snowmobilers reported the debris on the road to be about 1.8 m (6 ft.). A groomer moved through the area later that afternoon/evening and groomed over the debris preventing measurement of the actual debris on the road. Off the road, though, we measured debris from 70-100 cm (28-51 in.) the next day. The total snow depth at the crown measured 127 – 155 cm (50-61 in.). This is a relatively shallow snowpack for the entire advisory area, but not uncommon on southerly facing slopes at this elevation. The avalanche ran approximately 700 vertical feet, 1270 linear feet, and was about 900 feet wide at the widest extent of the crown (Figure 8 – 10).

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Figure 8: Image of the avalanche extent (white polygon). The avalanche debris crossed the Canyon Creek Road which is a terrain trap.

 

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Figure 9: Looking up at the looker’s left portion of the avalanche crown from below Canyon Creek Road near the toe of the debris. Crown denoted by red line. The rest of the crown extends out of the image to the right.

 

 

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Figure 10: A closer view of the crown at the location we investigated it. Red arrows point to the crown. The rumpled snow at the bottom of the arrows is a glide crack covered in new snow.

 

 

A member of a party involved provided information to the Flathead Avalanche Center. We appreciate the willingness of the individual to share this information, and are glad everyone made it safely out of this situation (Figure 11 and 12). Rider 1 was in a group of 13 that started at the Canyon Creek Winter Trailhead along the North Fork Road (Highway 486), north of Columbia Falls, MT. They traveled using snowmobiles along the groomed snowmobile trail (Canyon Creek Road) to their intended destination – the summit of Big Mountain at Whitefish Mountain Resort. Seven members of the party traveled ahead and the remaining six stayed back to recreate on the slopes along the way to their destination. Rider 1 stated that they rode to a popular slope to recreate on. This slope is located approximately 0.7 km (0.4 miles) to the east of where the Canyon Creek Road splits to the main road and the “high” road. Rider 1 climbed the slope on his snowmobile himself and there were already many tracks on the slope. Rider 1 rode back to the road. Rider 1 was traveling with his two sons (Rider 2 and Rider 3). Rider 1, Rider 2, and Rider 3 were sitting on the Canyon Creek Road when they noticed the slope fracture. Given that the area is a terrain trap there was nowhere to safely ride out of the avalanche. The avalanche hit Rider 1 and he was knocked about 150 feet downslope of the road. He mentioned that he had time to think “Wow! I’m in an avalanche.” He began swimming as he was taught. When he came to rest his helmet was packed with snow and he immediately could not breathe. He discovered his right hand was free and was able to move snow away from his face. Rider 2 was located in a position where the debris moved around him, but his snowmobile stayed put on the road. Rider 3, who was also initially on the road was knocked off his snowmobile and carried downslope where he was able to self-extricate. Rider 4 & 5 were both stuck uplsope of the road when the avalanche occurred and were both carried downslope as well. Rider 4  had an inflatable backpack (airbag) which he deployed and stayed above the snow and debris. Rider 5 was partially buried as well, but was able to self-extricate. Rider 6 was further to the west on the road and was just missed by the debris. Rider 1 estimates there were six to seven other people in the area, but only the above four were partially buried. All those that were partially buried were able to either self-extricate or were dug out with assistance (Figure 11-13).

 

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Figure 11: Location below road of Rider 1’s partial burial location. Rider 3 was buried to his waist next to the farthest tree to the right in image.

 

 

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Figure 12: Location of partial burial above road.

 

Figure 13: Partially buried snowmobile on the Canyon Creek Road.

Figure 13: Rider 2’s partially buried snowmobile on the Canyon Creek Road.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Rider 1 provided detailed information regarding background information. This was Rider 1’s third time visiting this area. The last time he visited the area was around the New Year holiday this year. They did not read the avalanche advisory, but talked to some folks beforehand that mentioned the elevated avalanche hazard. They are aware of the avalanche advisory, but never check it. They normally carry avalanche safety equipment (beacon, shovel, probe), but left this gear in the trailer on this day. They were intending to “go for an easy ride” to the summit of Big Mountain. Rider 1 mentioned that he never gave a thought to an avalanche occurring on that slope.

Rider 1 has been snowmobiling for more than 40 years. His avalanche training consisted of avalanche awareness classes at a local snowmobile dealership in his hometown. He always felt he was a very cautious rider. He mentioned he noticed the avalanche area sign posted along the Canyon Creek Road on the way out, but not on the way to their intended destination.

 

COMMENTS

The staff at the Flathead Avalanche Center wish to extend our gratitude to Rider 1 for his willingness to share this important, detailed, and personal information. This information helps all of us learn in the context of a real situation, and helps promote sound backcountry decision making.

Canyon Creek is a very popular winter backcountry recreation area for both motorized and non-motorized users. Given the high use in this area it is important to recognize the potential for avalanches to impact multiple individuals who may or may not be in your party. This area is a classic terrain trap where there is nowhere to escape should an avalanche occur. Thus, it is important to remember for everyone to practice sound decision making and always carry avalanche rescue gear.

 

SEARCH AND RESCUE

No search and rescue operations were initiated as the individuals involved were able to extricate themselves.

Direct any questions regarding this report to fac.admin@flatheadavalanche.org or 406.261.9873.

Report prepared by Erich Peitzsch and Seth Carbonari of the Flathead Avalanche Center.

REFERENCES

All formal notation and recording guidelines can be found in:
Greene, Ethan M., D. Atkins, K. Birkeland, K. Elder, C. Landry, B. Lazar, I. McCammon, M. Moore, D. Sharaf, C. Sterbenz, B. Tremper, and K. Williams, 2010. Snow, Weather, and Avalanches: Observational Guidelines for Avalanche Programs in the United States.  American Avalanche Association, Pagosa Springs, CO: Second Printing Fall 2010, 152 pp.

 

 


 

From 2/16/2014: Preliminary Information of Avalanche Incident in Canyon Creek – 2/15/2014.

Yesterday, February 15, 2014, a snowmobiler triggered an avalanche on a southeast facing (aspect 150 degrees) slope in the Canyon Creek drainage in the southern Whitefish Range. The slope the rider triggered the slide on is one of a series of southerly facing chutes known as the “Skook Chutes” or “Seven Sisters”. We investigated the avalanche today (2/16/2014). The avalanche failed on a layer of soft, faceted snow sitting on top of a hard, melt-freeze crust about 12 inches (30 cm) from the surface. It was approximately 900 feet wide, ran 700 vertical feet (from approximately 5930 feet to 5235 feet), and 1270 lineal feet. Avalanche debris reached and crossed the Canyon Creek Road, and was reported to be about 6 feet deep on the road. We measured other debris piles not on the road at 2.5 – 4.5 feet deep. The debris reached the creek bottom which is a terrain trap. The debris and bed surface were already covered by 2-8 inches of new snow overnight which made assessment slightly more difficult. 

The alpha angle (toe of debris to the crown of the avalanche) was 31.5 degrees. The average slope angle at the crown was 40 degrees. We are awaiting a conversation with an individual involved, but it was reported that 4 individuals were partially buried, and everyone made it out. 

The avalanche was classified:
SS-AMu-D2-R4-I (This translates to a soft slab (SS) avalanche triggered unintentionally by a snowmobiler (AMu). The avalanche rates 2 out of 5 on the destructive scale (D2) which means it could bury, injure, or kill a person. It was large relative to the path (R4), and failed at the interface between the new and old snow (I).)

 

 

We will post a full report when we have more information.