Accident: Summit

John Mountain – Accident Report
Kenai Mountains, Alaska

Location: John Mountain – Kenai Mountains
Lat/Lon: N 60.5735 W 149.5375
Date: February 13, 2024, time: 14:30
Report by: Chugach National Forest Avalanche Center (CNFAC)
Contact: staff@chugachavalanche.org, website: ChugachAvalanche.org

Avalanche Summary
On Tuesday, February 13, 2024, three backcountry skiers unintentionally triggered a large avalanche on John Mountain near milepost 41.5 along the Seward Highway in the Kenai Mountains. The skiers were ascending the slope when the avalanche occurred. The slab broke about 100 feet above them, catching and carrying all three skiers. Two of the skiers were partially buried and one was fully buried. The two who were partially buried sustained non-life-threatening injuries, were able to self rescue, and initiate a search for the other skier. Shortly after the fully buried skier was located, it was determined this skier did not survive. The avalanche failed in a weak layer of faceted snow roughly 1 foot deep on average and up to 2 feet deep at the crown where winds had loaded the upper slope.

Avalanche Information
Type: Soft Slab
Problem/Character: Persistent Slab
Crown Depth: 24”
Width: 150’
Vertical Run: 700’
Trigger: Skier
Weak Layer: 1mm Near-Surface Facets
Aspect: Northwest (300)
Elevation: 2600’ at crown
Slope Angle: 30-38 degrees
Slope Characteristics: Planar slope, below convex roll, sparse trees, alders, tundra in start zone.
Code: SS-ASu-R2-D2.5-O

Backcountry Avalanche Forecast
There is no daily avalanche forecast for this area. However, CNFAC publishes a ‘Weekend Avalanche Outlook’ for Summit Pass, where this accident took place. The most recent Outlook was issued on Friday, February 9, and was valid from February 10 to 11. The Bottom Line stated “A storm impacting Summit will produce strong winds and up to 6″ of new snow making it likely to trigger a wind slab avalanche up to 1′ to 2′ deep. It is also possible that storm snow and wind slabs may stress a buried weak layer enough to produce deeper and larger avalanches at all elevations, including lower elevation terrain.”, going on to mention “The weak sugary snow and surface hoar that formed during January’s period of cold clear weather is now covered by 1′ of snow. This weekend’s strong winds and new snow will add stress to this layer however, it may not be enough to cause natural avalanches. If that is the case then this layer may not show signs of instability until it is triggered. …[W]hile red flags such as cracking, collapsing, and recent avalanches can provide some information, persistent slabs may not give you any clues until they avalanche.”
Outlook Link: www.cnfaic.org/forecast/summit/02-09-2024

The closest daily avalanche forecast zone is for Turnagain Pass, which is 15 miles to the northeast. Although different avalanche danger can occur between these areas, on the day of the avalanche similar avalanche conditions existed. The avalanche danger on February 13 was HIGH at elevations above 1,000’ and CONSIDERABLE below 1,000’.
Forecast Link: www.cnfaic.org/forecast/turnagain/02-13-2024

Weather Summary
The significant weather events leading up to this accident can be traced back to early January. A dry spell with clear skies and cold temperatures from January 4 to 28 contributed to development of a widespread layer of near-surface facets. This layer was observed region-wide from the Western Chugach Mountains to Turnagain Pass and as far south as Seward. Between January 28 and February 4, the nearby Summit Creek Snotel station (3 miles north of the accident site) recorded 10” snow equaling 0.9” snow water equivalent (SWE). No precipitation occurred on 31 out of 35 days prior to the accident. The station recorded subzero temperatures (F) for 16 consecutive days from January 20 to February 4, with high temperatures in the single digits above and below zero during that time.

Snowfall returned to the area during the week prior to the accident. The Summit Creek Snotel station recorded 7” snow equaling 0.5” SWE, most of which fell on February 7 and 10. A significant wind event began to impact the area on February 12. The Sterling Wye ridgetop weather station above mile 37 on the Seward Highway (1.5 miles south of the accident site along a direct line) was not recording for a 22-hour window on February 12 as the winds were increasing, but was recording northeasterly winds averaging 15-20 mph with gusts of 25-30 mph during the 12 hours prior to the accident. Another ridgetop weather station at Mile 43 on the Alaska Railroad (14 miles east of the site) recorded easterly winds with average speeds of 20-35 mph with gusts of 40-55 mph during the 24 hours prior to the accident.

Snowpack Summary
The avalanche failed on a weak layer of 1 mm facets that formed during the previously mentioned January dry spell. This layer showed poor results in stability tests in a snowpit adjacent to the right flank of the avalanche during a field investigation the day after the accident (ECTP12, PST 30/100 END, CT13 SC). The layer was buried about a foot deep on slopes that had not been impacted by the strong winds over the previous week. It was closer to 2’ deep at the crown of the avalanche where windloading had occurred. Although no known avalanches had occurred on this weak layer in this area, public observations during the days prior had mentioned collapsing (whumpfing) in the snowpack.

The party noted that they did not see any recent loading on the slope as they were ascending, and it is likely the only portion of the slope that was loaded was the upper portion of the start zone where the slab released. With relatively soft snow on the surface in the majority of the avalanche path, the avalanche was able to entrain a large amount of debris relative to the size of the slope. The deeper sections of the debris pile in the deposition zones were 3-5’ (1-1.5 m) deep.

Accident Summary
Around 1pm on Tuesday, February 13, three backcountry skiers toured from MP 41.5 along the Seward Highway east toward John Mountain. They were planning to ski on a slope seen from the road that they had not been to before. Knowing there were strong winds along the ridgetops, they were hoping to find soft snow in sheltered terrain that was not steep enough to slide. All skiers had a minimum of Level 1 avalanche training and between 6-10 years of backcountry skiing experience.

As the skiers ascended they used their ski poles to probe the snowpack and their hands to perform quick ‘hand pits’. These are common informal tests to assess the snowpack layering and stability in the top foot of the snowpack. The skiers noted soft settled powder with some areas having a slightly stiffer ‘couple of inches’ of snow on top. They attributed this to either warming or wind. The party did not observe any signs of instability in the snowpack where they were traveling. They had read the Weekend Avalanche Outlook for this area (issued 4 days prior) as well as the Turnagain Pass avalanche forecast issued that morning. They were aware of a buried weak layer that existed region-wide.

The skiers continued skinning in a switchback fashion up the slope to where it began to get steeper. At this point the skiers decided to spread out so there was space between them. The snow surface was still soft without signs of wind loading. All three had avalanche airbags and they proceeded to arm them. Skier 3 took out their inclinometer and measured a slope angle in the low 30s with what appeared to be slightly steeper terrain further up the slope. Not wanting to be on steeper slopes, the group decided to head to a treed subridge, to the north, with a lower slope angle. As they made their way across the upper section of the slope to this safer spot they heard a loud crack. Skiers 1 and 3 recall looking up and seeing a large wave of snow about to overtake them. They reported not having time to turn their skis or attempt to get out of the way. All three were caught. Skiers 1 and 3 were carried for 25 to 30 seconds traveling ~1,300’ down the slope through patches of trees and alders (~600’ vertical distance). Skier 2 was caught in a small stand of trees higher on the slope and traveled ~500’ (~150’ vertical distance). Skier 3 describes having difficulty pulling their airbag due to the turbulent flow; it ultimately did not inflate. Skiers 1 and 2 were also unsuccessful in deploying their airbags. All three skiers were wearing avalanche transceivers and had probes and shovels in their packs.

Rescue Summary
Skier 3 was partially buried near the toe of the debris and Skier 1 was partially buried 50’ uphill from Skier 3. They were able to dig themselves out and immediately began searching for Skier 2 despite suffering injuries. They yelled incessantly, turned their transceivers to search, and found items from Skier 2 on the surface around 100’ downslope near the toe of the debris (a ski with a boot attached, pole, and helmet). Skiers 1 and 3 did not pick up a signal despite finding Skier 2’s items. They began a probe line where they thought Skier 2 would be located in the event Skier 2’s avalanche transceiver was damaged or had malfunctioned. After 10-15 minutes from the time of the avalanche Skier 3 called 911 (~2:45pm) and an organized rescue was initiated.

After the initial 911 call, Skier 3 began walking up the avalanche path while Skier 1 continued to probe in the lower runnout zone. After walking uphill for several hundred feet, Skier 3 picked up a signal and followed another couple hundred feet to a lowest point of 0.7 meters. At this point Skier 3 quickly found Skier 2 buried under 2 feet of snow in a small stand of trees. Skier 3 extricated Skier 2, who was unresponsive and had suffered trauma. Life-saving measures were attempted, which were ultimately unsuccessful.

While Skiers 1 and 3 were searching for Skier 2 a CNFAC avalanche forecaster was driving through the area. The forecaster was notified of the incident and was able to see the avalanche from the road. The forecaster and their partner skinned up to the site to assist, arriving around the time Skier 3 had recovered Skier 2. Four additional good samaritans also arrived at the avalanche site (all of whom had varying degrees of backcountry rescue, avalanche, and medical training). The authorities that responded were the Alaska State Troopers, US Forest Service Law Enforcement, Cooper Landing EMS, and Moose Pass EMS. Skiers 1 and 3 were assisted out of the backcountry around 7pm using snowmachines. They were taken to a local hospital via ambulance where they were later released. The deceased was transported off the mountain by rescue sled soon afterward and taken to the State Medical Examiner’s Office in Anchorage.

Comments
There were a few issues relating to avalanche rescue gear Skier 3 would like to share. One is his carbon probe began to fracture and splinter while probing, rendering the probe compromised but still somewhat functional. Second, the send/search switch on Skier 3’s beacon easily moved back to ‘send’ mode from ‘search’ mode. This caused the transceiver to stop searching and send a signal which Skier 1’s transceiver would pick up instead of Skier 2’s signal. This made it confusing and added difficulty to the transceiver search. Additionally, Skier 3 had added a carabiner to his airbag pack to make it easier to attach the crotch strap to the waist strap (CNFAC note: this is a common modification we have seen by many backcountry users). After the avalanche the carabiner had come off while being carried in the violent flow; it was non-locking. Although Skier 3 did not lose their pack they’d like the community to know the non-locking carabiner was not sufficient.

Avalanche Specialists with the Chugach National Forest Avalanche Center (CNFAC) obtained details of the accident during the rescue/recovery efforts, a site visit the following day, and through interviews with group members. We are incredibly grateful to Skiers 1 and 3 for sharing this difficult experience. We do our best to describe accidents such as this one to help the community better understand them in hopes of preventing future incidents.

Any questions should be directed to:
staff@chugachavalanche.org

Alaska State Troopers – Press Release
Media – Alaska Daily News