(CNN)The snowstorm that broke records and brought parts of the Rockies to a standstill had something else that was quite literally buried in the snow: a layer of brownish snow that fell in New Mexico and Colorado with dust that had traveled all the way from Mexico.It was a tweet from the National Weather Service office in Albuquerque, New Mexico, that pointed out the phenomenon.”The dust that was lofted this afternoon from the playas in Mexico … has now been transported all the way into Colorado!” it read. “We had a low that was tracking across the state and it was bringing a lot of gusty winds from the southwest. You could see on the satellite imagery the dust being lofted,” said Sharon Sullivan, meteorologist at the NWS in Albuquerque.
The yellow on the NOAA satellite shows the dust being carried north with the winds. Using a filtered layer created by Colorado State University, the dust is easier to pick out in the imagery.Dust even ended up in the snow as far north as Boulder, Colorado, according to the National Weather Service, which tweeted a picture of the brownish layer that fell outside its office.”We don’t see it too often. Especially ending up as far north as Boulder,” said Sullivan. More often, she added, dust will be carried from White Sands National Park, which is in the southern part of the state, but to get it from Mexico is pretty rare.
How the Mexican dust was able to travel so far
The weather setup for this event was perfect. Northern New Mexico and parts of Colorado have had a red flag warning in place for the past several days, so winds were gusting out of the southwest at 60-70 mph at times. Those strong winds helped lift and carry the dust from Mexico.”Some of these particles are very fine, so it only takes about 15-20 mph to have them lifted off the ground,” said Sullivan. So with winds gusting three times that, the dust was easily picked up and carried nearly 800 miles. Similar to the way Saharan dust travels from Africa, across the Atlantic and ends up suspended over the Florida sky, this dust was picked up and carried north. “The dust particles cling to the snowflake or water particle and falls with the snowflake to the ground,” said Sullivan. The result is a fresh coat of snow with a brown hue. Sullivan said the same setup Tuesday could result in more dusty snow, which she says also reduces the snow’s albedo, or reflection power, causing it to melt more quickly and resulting in a reduced snowpack overall. It has been a busy week for that region of the country. The National Weather Service office in Albuquerque had critical fire weather and winter weather advisories, and a tornado watch, at the same time — something that’s not unheard of for that region, but wild nonetheless.
Avalanche forecasting has come a long way since the 1950s, when forecasters relied solely on weather to predict when and where snow might slide. But it still requires scientists skiing and digging into the snowpack. That’s changing as satellites, aircraft-mounted sensors and ground-based remote monitoring fast-track the evolution of snow science, giving experts comprehensive insight into the uncanny nature of avalanches.
The Colorado Avalanche Information Center has been testing satellite imagery to detect avalanches. The technology is building a more accurate library of avalanche activity over a winter season, and year over year. And not just for the most trafficked zones, said Mike “Coop” Cooperstein, the center’s lead forecaster for the northern mountains.
“We have really good information along the highways, in the really popular recreation spots — Berthoud Pass, Loveland Pass, Red Mountain Pass. But it’s pretty close to the road,” Cooperstein said. “So we wanted to look into those deeper areas, a few miles from the trailhead, and see what’s happening, because we are forecasting for those areas.”
With 11 avalanche fatalities in Colorado this winter, and 32 nationwide, avalanche forecasters like those at CAIC need all the resources they can get to create accurate forecasts for backcountry regions. But methods of gathering good information are decades old. Emerging technologies may help, but it could be years before they are operational or affordable enough for avalanche forecast centers to use on a daily basis.
Relying on observations shared by travelers on roads and skintracks yields only a partial picture of avalanche activity, and doesn’t necessarily reflect the hazard spread across entire ranges. As a result, during any given avalanche cycle, forecasters may miss part of the avalanche activity because it wasn’t witnessed, and wouldn’t be able to warn their audience of backcountry goers. The other issue is not being able to verify whether their forecast was correct after the fact, making it difficult to identify patterns of inaccuracy and improve forecasts over time.
An avalanche record biased toward easy-to-access areas also leaves researchers in the lurch as they have only a fuzzy quantitative idea of what “normal” is as far as avalanches go. This could complicate understanding how avalanche activity shifts away from historical trends because of climate changes.
To balance and fill in the record, researchers, avalanche forecast centers and private companies are leaning on new technologies.
Late last year, Norway began using satellite-mounted radar to detect avalanches across the country.
The system was developed by a team from the Norwegian Research Center, known as NORCE, using synthetic aperture radar, or SAR, mounted on the European Space Agency’s two Sentinel-1 satellites. When a slide was detected it was automatically reported to Norwegian avalanche forecasters. Because the SAR device emits microwaves toward the Earth’s surface, rather than sensing natural light, this method allows the satellites to capture images on cloudy days or at night.
When an avalanche releases, the debris pile left at the slope’s base is both rougher and more dense than the surrounding snow, which scatters the microwaves emitted by the SAR so that fewer of them return to the sensor on the satellite. The NORCE team has built what’s called a data processing chain that recognizes this increased “backscatter” and flags it as potential avalanche debris.
The method is not perfect — with accuracy varying on how much water is in the snowpack — but technology is helping the Norwegian avalanche forecasting agency identify thousands more avalanches than any field-based efforts would, said Markus Eckerstorfer, the NORCE researcher who developed the data processing chain.
“In general, the method is very promising,” Eckerstorfer said. “It’s probably better than anything else. If you have a certain region, you could never cover the entire region as you do with a satellite. But you’re still not able to detect everything.”
In 2018, Eckerstorfer received funding from the ESA to test the method in Colorado, teaming up with CAIC. But the test fell flat.
Colorado’s mid-latitude played a role in the poor results: Because the Sentinel-1 satellites are polar-orbiting, moving between the North and South poles, the closer a region is to the equator, the less coverage it receives. Norway, being so far north, receives daily passes, while Colorado is passed every six or so days. Additionally, during the winter of 2018 one of the pair of satellites stopped sending images of Colorado because it needed time to recharge for imaging Europe and countries that paid to put the constellation into orbit.
An image every 12 days was far less useful for CAIC, and interest in the project dropped off.
“We wanted to have pretty close — a day or two at the most — of detection so that we can, after our forecast, look and see if what we think happened, happened,” Cooperstein said. “For that, there just isn’t enough coverage. There aren’t enough passes over Colorado to do that kind of work right now.”
Research using the method continues elsewhere in the states, though, which may one day come back to benefit Colorado.
An avalanche forecasting center in Idaho and another in Montana are using a rudimentary version of NORCE’s automated avalanche detection from Sentinel-1s, led by Zach Keskinen, a snow science master’s candidate at Montana State University.
Keskinen said the technology would not replace forecasters on skis, but it can be yet another tool in the high-consequence science of predicting avalanches.
“It’s starting to show promise to where [an avalanche forecaster] could say, ‘Hey, this is where you should go for your field day.’” he said. “Hopefully it will help to guide field days for forecasters and just make their field time more powerful.
Keskinen expects satellite coverage in the states to improve. The U.S.-Indian NISAR satellite scheduled for launch in 2022, will have SAR sensors.
Despite the low utility of radar in Colorado to date, satellites are still in the mix at CAIC. The organization is using optical imagery instead of radar to review the once-in-a-century avalanche cycle from March 2019, when historic slides swept over Interstate 70, blew out massive swaths of forest and spiked four of Colorado’s avalanche advisory zones into “extreme” avalanche danger.
“We can pick out avalanches from that cycle pretty well with, you know, 90% confidence that we’re picking out avalanches,” Cooperstein said.
CAIC staff can look at destruction of vegetation, or signatures of decaying vegetation, to see where an avalanche has cleared forest, documenting slides that may otherwise have been missed.
“The thing there is it takes such a large avalanche to destroy trees,” Cooperstein said. “That avalanche cycle, I’ll probably never see another one of those in my career, that’s that big. But [optical satellite imagery] has really good promise and we have pretty good results from doing that.”
Lasers can detect avalanches, too, specifically light detection and ranging, or LiDAR.
Jeffrey Deems, a researcher at University of Colorado and co-founder of Airborne Snow Observatory (an offshoot of NASA’s Jet Propulsion Laboratory), uses LiDAR mounted on aircraft to measure snow in basins across the western U.S. While the goal of these flights is to map how much snow—and therefore water—a river basin holds so that water managers can better plan how to allocate runoff, they also detect avalanches.
The method works by “mowing the lawn,” as Deems puts it, flying a plane with a LiDAR instrument scanning every foot of an entire river basin. Such a flight path is done in the summer without snow to create a baseline, then again in the winter, allowing Airborne Snow Observatories to subtract the summer image from the winter one to determine snow depth.
In 2019, flights in the Upper Gunnison and Roaring Fork river basins revealed large avalanches that had not been documented. LiDAR offers a more detailed look into an avalanche than other optical or radar imagery.
“With the LiDAR technology, we can actually see the change in snow depth, so we can actually get a better metric, or a better understanding of the volume of snow that had to move, rather than just mapping the extent of it,” Deems said.
Deems, with colleagues from the U.S. Army Cold Regions Research and Engineering Lab, operate ground-based LiDAR on Loveland Pass and Arapahoe Basin ski area as well, where the fixed sensors allow managers to measure every 10 centimeters of new snow and even slab thickness after a storm.
Private companies are supplying high-resolution satellite imagery as well, albeit with a price tag that’s beyond the budget of most avalanche forecasting centers.
Planet, one of the largest private satellite imagery companies, employs more than 130 satellites to provide clients with 3- to 5-meter resolution images, according to the company’s website. Clients can choose what geographic region they want covered, at what frequency — up to multiple times a day — and for how long a period.
Such rich data would no doubt benefit mapping avalanches and filling out the avalanche record, Cooperstein said, adding that the cost of such services are becoming more affordable.
In Colorado, field-based avalanche detection and forecasting — in which avalanche forecasters scour the mountains on snowmobiles and skis in search of the most unstable snowpack — aren’t going away any time soon. While these technologies are exciting, most aren’t operational, or simply cost too much for widespread use in Colorado’s diverse and wide-ranging backcountry.
“LiDAR and radar and camera technologies from ground-based or drone-based platforms, I think we’ll see those in increasing use for ski areas and highway departments who need real-time feedback on evolving conditions and the success of avalanche mitigation,” Deems said.
But the need for more avalanche-detection methods that are consistent from mountain range to mountain range and state to state remains if scientists and practitioners hope to better connect weather dynamics to avalanche activity, Deems added.
It may be key to planning for the future as well. Most mountain areas lack data-based projections of how climate will affect avalanche activity, because avalanche datasets are full of big holes, Eckerstorfer, the NORCE researcher, said. The sooner these datasets are filled in, the sooner plans can be formed to mitigate avalanches in a changing climate.
“If you live in a mountain environment, you need to start preparing now for what’s to come in a couple of decades,” Eckerstorfer said.
A final Colorado Avalanche Information Center report on the slide released Sunday provides details on the deadliest Colorado avalanche since 2013 capping a week where 15 backcountry travelers have died in slides across the U.S.
Communication challenges in a large group and a “terrain trap” were contributing factors in the deadliest avalanche in the state since 2013, according to the Colorado Avalanche Information Center’s report on the massive slide that killed three men near Ophir Pass in the San Juans on Feb. 1.
A skier who was buried but survived the avalanche on South Lookout Peak near Silverton that killed three of his friends described the torrent of snow that engulfed him like “a river.”
The report described the challenge of moving a large group — this one was seven skiers — through avalanche terrain as well as how “small communication errors and misunderstandings can be amplified in large groups.”
The report comes after the deadliest week for avalanches in the United States in more than a century. Counting this South Lookout Mountain tragedy and a slide in Utah’s Millcreek Canyon on Saturday that killed four, 15 people have died in avalanches in the country in the last seven days.
Three men — Adam Palmer, Seth Bossung and Andy Jessen — were buried and killed in the avalanche. They were among a group of Eagle County locals visiting the Opus Hut. The crew had been skiing in the backcountry around Red Mountain Pass and skied out of Silverton Mountain’s helicopter on Sunday. They skied into the Opus Hut around 1 p.m. on Monday and spent about an hour at the remote cabin before venturing out for an afternoon tour.
Some of the skiers, like Palmer, had been part of the annual trip to Opus for many years. Others, like Jessen, were new to the trip. All were friends from back home in Eagle. As they left the hut, the caretaker said there had been “lots of [avalanche] activity on all aspects and today is the warmest day since December,” according to the report by CAIC forecasters Spencer Logan, Jeff Davis, Rebecca Hodgetts and Mike Barney.
The crew climbed a short stretch and skied a southwest-facing slope into the drainage between Ophir Pass road — which is closed in winter — and The Nose, a descent on the skier’s left of South Lookout Peak. They climbed to a ridge toward the top of the The Nose and stopped at a saddle around 11,800 feet. They decided to ski a sparsely treed slope and skied one at a time with a plan to regroup on a small knob just above a steep-walled gully at the bottom of the peak’s face.
“Before the entire group collected on the knob, the first skiers to arrive began skiing down the rest of the slope and into the gully,” reads the report.
Palmer, Jessen, Bossup and the unnamed fourth man descended the gully, which the report describes as a “terrain trap.” One of them stopped on the right wall of the gully and the fourth skier yelled for him to avoid the steep section of the gully on the right side. All four men were moving down the gully when the avalanche released around 3:20 p.m.
The report says the avalanche came in two waves. The fourth skier was able to pull his avalanche airbag when the first wall of snow released and he was standing in the bottom of the gully when a second wave hit him from behind.
“He was engulfed in snow and tumbled violently,” the report says.
The remaining three skiers were able to find the fourth man, whose airbag was visible above the debris. Palmer, Jessen and Bossung, however, were completely buried.
The four skiers sent an SOS signal on an InReach device around 4:40 p.m. and they were able to detect signals from their friend’s avalanche transceivers. But the closest signals they could detect on their transceivers were between 4 and 5 meters, or about 13 to 16 feet. (For transceiver searching, the digging begins at the lowest reading, which is the closest point to the buried skier.) The four men dug for two hours.
Inside the holes, the signals from the transceivers showed their friends still 5-to-6 feet below. They were able to touch one of their friends with a probe pole from within one hole.
At nightfall, the four men were exhausted and made the “difficult decision” to return to the hut, reads the report. They built snowshoes out of tree branches for the fourth skier who lost his skis in the slide. Around 7:30 p.m. they made contact with San Juan County Search and Rescue members who had organized around 5 p.m. after getting the group’s distress call. The rescuers brought the four men back to the trailhead and suspended search operations until the following morning.
Searchers recovered two of the men on Tuesday as the Helitrax helicopter operation dropped explosives onto adjacent slopes, triggering several large avalanches. The search team of more than 30 people returned on Wednesday and recovered the third skier. One of the men was buried 9 feet deep. Another was at 11 feet. And the third was buried 20 feet deep in the gully.
The Colorado Avalanche Information Center provides comments on all its fatal accident reports, hoping that insight into the events leading up to the avalanche can help other backcountry travelers avoid getting caught in a slide.
Ethan Greene, the director of the Colorado Avalanche Information Center, describes his reports as akin to a newspaper. There are the news reports and the editorial section. In this avalanche, the forecasters highlighted the difficulty in communicating with a large group. Four of the skiers began their descent of the gully before the rest of the skiers arrived at the knob.
“Yet Rider 1 started down the gully before the rest of the group arrived,” the report says. “He was quickly followed by Riders 2, 3 and 4. There were suddenly four riders in the gully, all out of sight of the people on the knob when the avalanche released.”
“Gullies are bad places to be,” Greene said in an interview Sunday. “A lot of guides and avalanche professionals just avoid them altogether.”
Greene said his staff can’t point to the communication breakdown as a cause for the accident “but it’s definitely something that came out of the discussion that staff had with the people in the group.”
Greene and his team have been working hard this season, which has seen eight people buried and killed in Colorado avalanches, with more winter to come.
A weak layer of snow buried deep in the snowpack is shedding slabs of new snow. As more snow falls, the stress on that weak layer grows and avalanches hazards rise.
This is not a normal year, Greene said, who estimates the increased avalanche danger this season is maybe a 1 in 10 occurrence. So, for a skier who has spent 20 years in the Colorado backcountry, this is likely the second time to see this level of widespread avalanche hazard.
“This is the year to keep things mellow,” Greene said. “This is frustrating for us. Obviously we are not doing enough, but we have been doing everything we normally do plus an incredible amount more. It’s hard to know how successful we are. Maybe if we were not doing what we are doing, things would be worse. But eight people dead by the first week of February — this is not a good place to be.”
Events Leading to the Avalanche
On Monday, February 1 a group of seven friends met in Silverton for a multi-day trip to a backcountry hut east of Ophir Pass. They ranged in age from mid 30s to mid 50s. Some had been backcountry skiing together for many years, while others were new additions to the group. Several of them had made annual trips into this hut for at least ten years. Four members of the group had been in the area since Friday skiing in the backcountry and with a local helicopter skiing operation. Three members of the group arrived Sunday evening.
The group left Silverton around 10:30 AM and drove to the winter closure of CR8 (Ophir Pass Rd). At the trailhead the group checked transceivers and discussed avalanche conditions. They left the trailhead around 11:30 AM. They identified the south-facing slopes above CR8 as a potential avalanche hazard and traveled one at a time below them to reduce their exposure. They arrived at the hut around 1:00 PM and spent about an hour there before heading out for an afternoon tour.
The group discussed assessing avalanche conditions on a terrain feature known as The Nose, which is between Crystal Lake and the Middle Fork of Mineral Creek. On previous trips they had skied this slope, but did not plan to ski it that afternoon. Before leaving the hut they talked with the hut keeper who said there had been “lots of [avalanche] activity on all aspects, and today is the warmest day since December.”
They left the hut and climbed a short distance before descending a southwest-facing slope into the drainage between CR8 and The Nose.They climbed a gentle ridge to the south heading towards The Nose.They reached a small saddle at about 11,800 feet, and decided to descend a northeast facing, sparsely treed slope. The group rode down one at a time and started to regroup on a knob just above a steep-walled gully at the bottom of the slope. Before the entire group collected on the knob, the first skiers to arrive began skiing down the rest of the slope, and into the gully towards the Middle Fork of Mineral Creek.
Rider 1 skied down from the knob and into the gully. Riders 2 and 3 followed the same path, skiing close to each other. While Rider 2 continued down the gully, Rider 3 stopped along the skier’s right wall. Rider 4 slid over the convex roll at the gully entrance to yell down, telling Rider 3 to move to the left side of the gully and avoid the steeper slopes on the right. All four were moving down the gully when the avalanche released at about 3:20 PM.
The avalanche caught Riders 1, 2, 3, and 4. Rider 4 described the avalanche as two waves. The first wave slowly pulled him into the gully, but he was able to stay on his feet. Thinking there was enough snow to bury him if he fell over, he deployed the avalanche airbag on his backpack. After the snow stopped he was standing in the gully. Seconds later a larger wave of snow hit him from behind. Rider 4 immediately lost his skis and poles. He was engulfed in snow and tumbled violently. “It felt like I was in a river and I was fully under the snow for approximately 15 to 25 seconds” Rider 4 explained, and was “moving very fast a significant way down the gully”. When the avalanche stopped, Rider 4 was buried in the debris with his head under the snow, but a portion of his airbag was visible on the surface (partially buried-critical). Riders 1, 2, and 3 were completely buried in the avalanche debris.
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 factors that may have contributed to the outcome. We offer these comments in the hope that it will help people avoid future avalanche accidents.
Moving a large group through avalanche terrain one at a time requires considerable time and careful coordination. Small communication errors and misunderstandings can be amplified in large groups. This challenge may have played a role in this accident. Some of the party expected everyone to regroup on the knob above the gully, yet Rider 1 started down the gully before the rest of the group arrived. He was quickly followed by Riders 2, 3, and 4. There were suddenly four riders in the gully, all out of sight of the people on the knob when the avalanche released.
The avalanche caught the four riders in a narrow gully where debris piled up extremely deep. Rider 4’s position higher in the gully, staying more skier’s left, and his airbag likely all reduced his burial depth. The others were not as lucky, and were deeply buried. In a terrain trap like this gully, the depth of avalanche debris can vary dramatically over a very small distance.
Digging a person out of avalanche debris is by far the most time consuming portion of a rescue. Deep burials are very difficult for a small team to manage. The debris is almost always very hard. Equipment breaks, people tire quickly, and just managing the snow you are removing becomes a monumental task. The four riders worked for hours and only got through the top half of avalanche debris above the victims. Anyone who has dealt with avalanche debris over a few feet deep will tell you the digging gets more difficult and more complicated the deeper you go. Eventually it took an organized search and rescue group, with many people and power tools, two days to recover all three riders.
The group and search and rescue personnel both detected two transceiver signals in close proximity at one of the burial sites. This led them to believe that Riders 2 and 3 were buried very near each other. They eventually determined the signal came from a single avalanche transceiver that was over 10 years old. Over the last 10 years the standards for avalanche rescue transceivers have improved. Although not common, modern transceivers can sometimes recognize the signal from certain old transceivers as two signals, a primary and ghost signal. In this case the age of the skier’s rescue device did not play a significant role in the outcome of the accident. However, it is a good reminder to make sure you understand the performance of the equipment you and your partners are using. Most avalanche rescue organizations and transceiver manufacturers recommend retiring devices that are more than 10 years old.