- Location: Green Mountain, Express Creek
- State: Colorado
- Date: 2019/01/21
- Summary Description: 1 backcountry tourer caught, buried, and killed
- Primary Activity: Backcountry Tourer
- Primary Travel Mode: Ski
- Location Setting: Backcountry
- Caught: 1
- Partially Buried, Non-Critical: 0
- Partially Buried, Critical: 0
- Fully Buried: 1
- Injured: 0
- Killed: 1
- Type: SS
- Trigger: AS - Skier
- Trigger (subcode): u - An unintentional release
- Size - Relative to Path: R3
- Size - Destructive Force: D2.5
- Sliding Surface: O - Within Old Snow
- Slope Aspect: NE
- Site Elevation: 11150 ft
- Slope Angle: 35 °
- Slope Characteristic: Convex Slope,Ridgeline,Sparse Trees
This was a soft slab avalanche unintentionally triggered by a skier, medium-sized relative to the path,and had the destructive force to bury, injure, or kill a person, and break some small trees (SS-ASu-R3-D2.5-O). The skier triggered the avalanche near the skier's right flank, but the avalanche quickly propagated across and up the slope, breaking 150 to 200 feet above the descending skier.
The avalanche broke on a buried layer of near-surface facets that developed between storms in mid –December. In some places, it stepped down to deeper weak layers near the ground. The face of the crown ranged from 24 inches to 48 inches deep. The avalanche broke approximately 400 feet wide and ran around 400 vertical feet (600 linear feet). The avalanche released on a north-northeast facing slope around 35 degrees in steepness.
This was a Persistent Slab avalanche.
Backcountry Avalanche Forecast
Persistent Slab avalanches were listed as a problem in the Colorado Avalanche Information Center’s (CAIC) Aspen zone forecast since November 14. In the ten days before this accident, the avalanche problem list included Persistent Slab avalanches at all elevations on northwest, north, northeast, east, and southeast aspects. The CAIC issued an Avalanche Warning on January 16 and again on January 18 for a second storm event.
The Avalanche Warning expired on January 19, and the CAIC issued a Special Avalanche Advisory through Monday, January 21. It read:
A Special Avalanche Advisory is in effect for the mountains of Colorado through Monday, January 21. Avalanche conditions are dangerous. Backcountry travelers can easily trigger very large and deadly avalanches. Avalanches may break across terrain features and run long distances. Since January 11, the CAIC has documented 10 people caught in avalanches, 44 avalanches triggered by backcountry travelers, and over 280 avalanches in total. Backcountry travel this weekend will require conservative decision making, cautious route finding, and careful snowpack and terrain evaluation.
On the day of the accident the, CAIC’s backcountry avalanche forecast for the Aspen zone rated the avalanche danger as Considerable (Level 3) near and above treeline and Moderate (Level 2) below treeline. Persistent Slab avalanches was the only avalanche problem. It was highlighted on northwest, north, northeast, east, and southeast aspects near and above treeline, with a Likelihood of Likely and Size ranging of Large to Very Large (up to D3). The Summary statement in the forecast said:
Natural avalanche activity is winding down, but many slopes are ripe for human-triggering today. A skier-triggered avalanche near Snowmass yesterday provides our most recent evidence. Many recent avalanches broke several feet deep, traveling across terrain features and running long distances. You can trigger these avalanches from a distance, on adjacent slopes or from below. The largest and most dangerous slopes are near and above treeline and face northwest to east through southeast, where strong winds have drifted snow into thick, dense slabs. Avalanches on other aspects and at lower elevations are harder to trigger and will generally be smaller in size, but can still have enough volume to carry or bury a person.
Watch for and avoid all steep slopes and cross-loaded terrain features with a smooth, pillowy appearance. Shooting cracks, whumpfing and collapsing are clear signs of unstable snow. Slopes less than about 30 degrees, without steep, connected slopes around or above you offer safer riding options.
Ski areas near the accident site measured significant snowfall during the week before the accident. Aspen Mountain (8.6 miles to the north) measured 16 inches of snowfall, Aspen Highland (9.2 miles to the north northwest) measured 24 inches, and Snowmass (13 miles to the northwest) measured 17 inches. The Schofield Pass SNOTEL site (14 miles to the west), measured around two feet of snow and 3.2 inches of snow water equivalent (SWE), and the Upper Taylor SNOTEL site (3 miles to the southeast) recorded 15 inches of snow and 1.4 inches of SWE.
The significant snowfall came during two storm events in the five days before the accident. The first storm began on January 16. Twenty-four hour snow totals on the morning of January 17 were around 9 inches of snow and 0.9 inches of SWE at the ski areas, and at 1.2 inches of SWE at Schofield Pass. A brief lull in snowfall on January 17 was accompanied by strong southwesterly winds. The Aspen Highland Loge station (elevation 11,625 ft) recorded sustained winds of 15 to 25 mph, with gusts in the 40s. A second storm arrived overnight January 17 and into January 18. Storm totals on the morning of January 18 were 6 to 10 inches of snow and 0.5 to 1.5 inches of water. This second storm came in with strong southwest winds that shifted to the northwest by the afternoon of January 18. Wind speeds throughout the event stayed in the 15 to 25 mph range with gusts in the 40s.
Periodic light snowfall and light westerly winds prevailed until the afternoon of January 20, when southwest winds strengthened ahead of an incoming storm system. Winds speed increased to 20 to 30 mph with gusts in the 50s overnight and into the early morning hours of January 21. On the day of the accident, winds were 10 to 20 mph from the southwest and temperatures in the teens. Light snowfall began that morning and intensified by the afternoon.
October snowfall turned into weak and faceted snow during dry weather in the first two weeks of November. Rain events washed away the snow on low-elevation slopes and it melted away on many south and west-facing slopes. North and east-facing slopes above about 10,500 feet held the most early season snow. Small storm events in mid-November and a large storm around Thanksgiving built stiffer slabs above these weak layers. The Thanksgiving storm spurred the first widespread avalanche cycle of the season in the Aspen zone, including a few close calls near the Aspen ski area. The CAIC recorded 17 avalanches from November 24 to 26 during this first substantial loading event. Mostly on slopes with a north and east aspect.
A pronounced layer of near-surface facets formed during a sustained dry period in mid-December. A snow storm around Christmas buried this persistent weak layer, preserving it in the snowpack. Additional storms arrived around New Year’s Day and again on January 6 to 7. These storms built additional slabs, and contributed to a significant increase in avalanche activity in the Aspen zone. The CAIC documented 34 avalanches between December 31 and January 9.
Modest snowfall through mid-January continued to build the slab over the persistent weak layer. On January 11, a backcountry tourer triggered an avalanche and was caught and partially buried (critical) on a northwest-facing slope above the Lindley Hut, 2 miles to the southwest of the accident site. Two major loading events in the days leading up to the accident formed additional slabs 2 to 4 feet thick, and spurred another round of avalanche activity. The CAIC documented an additional 25 avalanches in the Aspen zone between January 16 and January 20. The layer of near-surface facets buried by the Christmas storm was the culprit weak layer in many of these avalanches.
Events Leading to the Avalanche
A group of 6 (two couples, each with one young child) met on the morning of Saturday, January 19 in Ashcroft to head into the Markley Hut, a little over two miles up the Express Creek Road. Their original plan was to go to the hut on Friday, but they postponed their trip by a day due to the Avalanche Warning in effect that day. The route to the hut passes under avalanche paths on Ashcroft Mountain. Avalanches in these paths can reach the Express Creek Road.
On Saturday and Sunday the group skied on and around Green Mountain (point marked 12054 on USGS maps immediately south of the hut). They typically skied in groups of two, while the other two adults stayed behind at the hut with the young children. The first two days of skiing were enjoyable and uneventful. On Saturday, two of the skiers experienced a collapse on a northwest-facing sloping on the opposite side of the ridge (marked 11490 on USGS maps) from the accident site, but otherwise they did not observe any signs of instability. They skied multiple laps, without incident, on the low-angle, skier’s left (west) margin of the slope that would later avalanche on Monday.
On Monday morning, January 21, Skier 1 and Skier 2 left the hut around 6:30 AM. They skinned along a ridgeline to the top of Green Mountain to get some early-morning views. They skied back down the ridgeline and decided to wrap around to the south of a rock outcrop at point 11490. This put them on the opposite, skier’s right (east), side of the slope the group skied the prior two days. Skier 1 descended a short way through dense trees and stopped in a spot where he had a good view of Skier 2’s intended descent. Skier 2 came down through the trees and continued down. He skied around 150 to 200 vertical feet when he triggered the avalanche.
The avalanche quickly propagated several hundred feet across the slope and the crown released approximately 150 to 200 feet above Skier 2, near where Skier 1 was standing. Skier 1 yelled “avalanche” but wasn’t sure if Skier 2 heard him. Skier 1 lost sight of Skier 2 as the debris began flowing down the slope to were the terrain was a little steeper. Skier 2 was still upright on his skis when Skier 1 lost sight of him.
Skier 1 quickly stepped onto the bed surface, still in his skis. He turned his beacon to search but did not have a signal. He began traversing the bed surface and picked up a signal within a minute or two. He followed the signal to a small but dense cluster of trees. There were no surface clues. The trees made the fine search difficult and Skier 1 was not sure if Skier 2 was upslope or downslope of the trees. After a minute or so, he determined that Skier 2 was on the downhill side of the trees. He assembled his probe and tried to pinpoint Skier 2. Again, the trees made using the probe difficult as the probe repeatedly got stuck in the overhead branches. Skier 1 abandoned probing and began to dig at the point of his lowest beacon reading.
Skier 1 found Skier 2’s arm. Skier 2 was on his right side with his head downhill. He was not breathing and did not have a pulse. He had one ski still attached and the other was missing. Skier 1 exposed Skier 2’s airway about 10 minutes after the avalanche. Skier 1 extricated Skier 2 from the snow. He performed CPR for 5 to 10 minutes before deciding to alert the two adults at the hut, located less than 1/3 of a mile from the site. Skier 1 then quickly returned to the accident scene with Skier 2’s spouse.
Almost immediately after these two left the hut to return to the accident scene, a guide and a client passed by the hut on a day trip. The last remaining adult at the hut explained the situation to the guide who alerted the authorities at 10:00 AM (the guide was a member of Mountain Rescue Aspen (MRA) and was carrying a radio). The guide and his client arrived at the accident site at 10:15 AM. The guide made a second radio call at 10:19 AM reporting a potential fatal accident. The four on scene continued CPR for an additional 30 minutes, but their efforts were not successful. They left the scene around 10:50 AM and returned to the hut to wait for additional personnel from MRA.
All of the fatal avalanche accidents we investigate are tragic events. We do our best to describe each one to help the people involved and the community as a whole better understand them. We offer these comments in the hope that it will help people avoid future avalanche accidents.
The two skiers involved in this accident were fathers and husbands of the other group members staying at the hut. Their mindset was risk adverse. Their goal for the day was to get outside, get some exercise and good views, and descend some safe, soft snow back to the hut on the last day of their trip. The adult members of the group had skied near and along the skier’s left flank of the avalanche slope in the two days leading up the accident without incident. Their only sign of instability was one collapse on a northwest-facing slope, on the opposite side of the ridge from the avalanche slope, two days before the accident.
The descents they made along the avalanche slope in the previous two days were in lower-angled terrain. They skied on slopes near and less than 30 degrees in steepness without incident. The lack of obvious signs of instability, and numerous safe descents in the lower-angled portions of the slope likely made them feel more comfortable with this particular terrain feature. On the day of the accident they descended into steeper terrain, around 35 degrees in steepness, on the skier’s right side of the slope.
This is only four or five degrees steeper than the terrain they had been skiing. It may not seem much steeper, but in this case it made a very important difference. On some days and with some avalanche problems, the difference between 30 degrees and 35 degrees might not be significant. However, it can be significant when dealing with a Persistent Slab avalanche problem, especially when remote triggers and triggering from well down the slope is possible. It is not uncommon for humans to move into more risky terrain when there is no feedback to suggest things are dangerous. It is hard to recognize this slow drift when you are making a series of decisions throughout a day in the field.
One method to help combat our human frailties is to employ a repeatable decision-making process before entering the field. Use trip plans and checklists and rule out potentially dangerous terrain before you go out. Stick to the plan in the field, no matter how enticing that terrain feature might look. Making terrain choices in the field without a written and agreed upon trip plan has contributed to many accidents over time. We are all human and easily lured into new areas with better snow, a better line, or just a place that doesn’t seem consequential from the current vantage point.
Skier 2 was wearing non-releasable telemark bindings. One ski did come off in the course of the avalanche, but he was buried with one ski still attached. It is impossible to know whether this contributed to his burial, or increased his burial depth (approximate burial depth was 150cm), but we do know that having things attached to your feet or hands increases the chances you get pulled deeper into the avalanche debris. It is generally safer to use releasable bindings, and to not use pole straps while traveling in the backcountry.
Our investigation included a site visit hours after the accident occurred, and interviews with the involved MRA members and the surviving witness. We greatly appreciate their contributions, and willingness to discuss a very tragic and painful event.
Figure 18: Snow profile taken along the skier's left flank of the avalanche hours after the accident. Jan 21, 2019