by Brian Lazar

Despite more modest snowfall than we saw across the state in December, we ended the first month of 2020 with the Snow Water Equivalent (SWE) over 100% of the long-term median across all of Colorado’s river basins. January had light and fairly continuous snowfall, characterized by several small to mid-size storms and interspersed with short dry spells. Crusts and weak layers formed in the upper snowpack during these dry spells. Each loading event of more than a few inches of snow spurred some avalanche activity. The month also saw several very strong wind events which dramatically altered the alpine landscape and redistributed snow in many areas.

The CAIC recorded 648 avalanches in December. One hundred and twenty nine of those avalanches were human triggered. Twenty-three people were caught in avalanches during the month, including 11 people in one week between January 18 and January 25. Five people were partially buried, 3 were injured, and tragically, one person lost their life when they were hit with a mix of falling ice and snow. This was the second avalanche fatality in Colorado of the 2019-2020 season.

The first storm of the month dropped 8 to 12 inches of snow from January 2 to January 4. This led to our first avalanche cycle of the month, including our first avalanche involvements. Avalanche incidents during this period were concentrated in the Northern Mountains. A skier triggered and took a short ride in a small avalanche on Loveland Pass on January 2. A similar incident occurred in Rocky Mountain National Park on January 5. Also on January 5, a skier triggered a small avalanche on Coon Hill on the west side of the Eisenhower Tunnel and was carried several hundred feet before coming to rest. A few days after the storm ended a CAIC forecaster triggered and took a short ride on the south side of Coon Hill as well. Fortunately, no one was buried or injured in these incidents.

We had a four to five day dry spell after Jan 5, along with very cold temperatures. This formed a very weak layer of near-surface facets in most mountain locations. This near-surface weak layer showed its potential to produce avalanches when the second notable storm system arrived in the second week of January. This storm dropped between 4 to 8 inches of snow in most mountain areas between the 10th and the 14th, with snow coming earlier in the San Juan Mountains and later in the Central and Northern Mountains. This modest loading event led to a fairly widespread avalanche cycle.

There were 35 reported avalanches in the Northern Mountains. Eleven of those avalanches were large enough to injure a person. Most avalanche activity occurred on north to east to south-facing slopes. We received reports of one partial burial near the Eiseman Hut on January 10. There were no other avalanche involvements during this second storm.

The CAIC recorded 49 avalanches during this time period in the Central Mountains, 31 of these avalanches were large enough to injure or kill a person. The CAIC also recorded 29 avalanches in the Southern Mountains all of which were large enough to kill or injure a rider. Similar to the Northern Mountains, most avalanches in the Central and Southern Mountains occurred on northwest to east to south facing slopes.

We had another dry spell from January 15 to 18, when our third notable storm system arrived. It wasn’t a big system to start, dropping only around 6 inches of snow in most mountain areas by January 19, but this was quickly followed by a bigger system on January 22 and 23, which added another 7 to 14 inches of snow. This one-two punch kicked off our most concentrated week of avalanche incidents during the 2019-2020 season.

The Steamboat area, which had seen little activity outside of small storm-snow avalanches up to this point, reported its first large skier-triggered Persistent Slab avalanche on January 19, breaking 3 feet deep on the January 9 layer. Between January 19 and 25, 8 people were caught and carried in avalanches in the Northern Mountains. Two partially buried. One of these was a climber in Rocky Mountain National Park who triggered an avalanche and was washed over a 50 foot cliff. Fortunately, this resulted in only minor injuries. A backcountry skier was also seriously injured after being caught and carried in a large avalanche near Jones Pass on January 22.

In this same week a skier was caught and carried in an avalanche in Red Lady Bowl above Crested Butte. In the Southern Mountains an ice climber was killed in the Uncompahgre Gorge on January 18 after an ice pillar broke loose, entrained small amounts of loose snow, and hit a climber with chunks of ice and snow, burying here in the creek below. This was the second avalanche-related fatality in Colorado of the 2019-2020 season. The week closed out in the Southern Mountains with a snowmobile triggered avalanche near Molas Pass that caught and carried a rider.

After January 25, Colorado saw another brief dry spell before our fourth and final modest storm system arrived on January 27. Once again the storm differed slightly in timing but was egalitarian in delivering around 7 to 14 inches of snow to most mountain areas through January 28. This kicked off yet another avalanche cycle and another round of avalanche incidents.

The CAIC documented 21 avalanches in the Northern Mountains during or immediately after the fourth storm. Nine of these avalanches were large enough to kill or injure a person. All of these avalanches occurred in the Vail-Summit and Front Range zones. Two people were caught in avalanches including an on duty patroller. There were 14 avalanches in the Central Mountains, 3 were large enough to kill or injure a person. A snowmobiler was caught and partially buried on January 20 near Kebler Pass west of Crested Butte. The CAIC received reports of 23 avalanches in the Southern Mountains. Thirteen were large enough to kill or injure a skier. Three people were caught in avalanches in two separate incidents in the South San Juan Zone.

We closed out January with only a few avalanches breaking near the ground. Most avalanches released in storm or wind-drifted snow, or on weak layers buried in the middle of the snowpack. Basal weak layers remained a concern in our thinner snowpack areas, but it was going to take larger loading events to see deep avalanches.

by Brian Lazar and Ethan Greene

Santa delivered a lot of snow to Colorado in the past two weeks, just in time for Christmas. Have we been naughty or nice? Well riding conditions have been fabulous, but there have been some impressive avalanches.

The last storm brought significant snowfall and avalanche activity, but since then the snowpack has been getting stronger and we’ve seen fewer avalanches and less cracking and collapsing.  Paradoxically, this does not mean things are necessarily safer for the backcountry traveler. The likelihood of triggering an avalanche is decreasing, but the size and consequences of avalanches that do release are steadily increasing.  This trend has prompted discussions amongst our forecasters about whether or not we are moving into a new risk paradigm, and perhaps, a new avalanche problem: Deep Persistent Slab (DPS) avalanches.

DPS avalanches have many characteristics in common with Persistent Slab (PS) avalanches. Both break on persistent weak layers. You can trigger both remotely and from low-angle slopes. Both of these types of avalanches can fail in surprising ways, breaking across and around terrain features that would contain a Storm or Wind Slab avalanche. PS and DPS avalanches have a lot in common, but there are some very important differences that affect how we avoid them and manage our own personal risk.

DPS avalanches are low probability and high consequence events. The likelihood of triggering a PS avalanche and the size of that avalanche can vary over a wide range. DPS avalanches are a specific creature, very large in size and hard to trigger.  We look for three things before we add it to our list of Avalanche Problems. Those three things are:

• Avalanches will be  stubborn to trigger,  Unlikely or Possible on the Likelihood scale
• Avalanches will be destructive,  D3 or larger
• Avalanches will break on deeply buried or basal weak layers

These criteria capture the low-probability/ high-consequence nature of DPS avalanches.  A low Likelihood means there will be very few or no natural avalanches, human-triggered avalanches will be unlikely, and large explosive and cornice triggers will only produce some results (ADFAR2).  A D3 (Very Large) avalanche could bury and destroy a car, damage a truck, destroy a wood frame house, or break a few trees. When the likelihood slider drops towards “Unlikely” and the size slider climbs to “Very Large or Historic”, we have a DPS avalanche problem (see image below).

DPS avalanches are especially scary because most people don’t have much experience dealing with them.  It is hard to gain experience dealing with these beasts because we don’t see DPS avalanche cycles that often. In a typical year we could see over twenty cycles of Storm, Wind, and Persistent Slab avalanches, but we may only see one DPS avalanche cycle in five years.  You could navigate through two Storm Slab avalanche cycles in a week of touring, but it could take you ten years to gain the same amount of experience with DPS avalanches. These avalanches are also very large and extremely dangerous. Most people that get caught in one get killed.  This makes it very difficult to learn from a close call. Your first encounter with a DPS avalanche could very well be your last.

Over the last 15 years, almost all avalanche accidents in Colorado where more than one person died were the result of a DPS avalanche. In two seasons with pronounced DPS avalanche cycles (2008-09 and 2012-13), DPS avalanches accounted for more than 60% of the avalanche fatalities.  In the figure below (covering two seasons: 2012-13 and 2013-14) you can see that avalanches involving persistent weak layers are particularly dangerous. DPS avalanches only accounted for 5% of the observed avalanches, but caused 42% of the fatalities.  Sure sounds like low-probability/high-consequence, doesn’t it?  You can read the whole study here.

In a year with DPS avalanches we can describe the forecast zones where they could happen and the aspect and elevation of the slopes that are most likely to produce one. This is the good news. The bad news is that if you have ten of those slopes, it is really hard to predict which one will produce a DPS avalanche. This is the low probability part. Remember the other half of the description is high consequence. Because DPS avalanches are so dangerous, the only safe way to manage your risk is by avoiding those suspect slopes. On a bad year, you might have to avoid those slopes for the rest of the season. This can be hard to do because people will test suspect slopes, and most will get away with it (they are low-probability events). And due to the nature of a DPS avalanche problem the danger is almost always MODERATE (Level 2) when this is our main avalanche problem, because these avalanches are hard to trigger. That combination -people testing slopes without immediate consequences and a MODERATE (Level 2) rating – doesn’t scream “dangerous” the way an avalanche warning does.

So where are we this year?  In some places we can produce D3 avalanches, as demonstrated by the mid-December avalanche cycle.  Between December 14 and 21, multiple D3 avalanches released in the Aspen, Gunnison, North San Juan, and Front Range zones. This includes both natural and human-triggered slides.  Around half of these avalanches ran naturally during and shortly after the storm cycle. So while we met the size criteria, we weren’t at the point where we called these avalanches stubborn to trigger. Instead, we had Likely to Very Likely, and Large to Very Large PS avalanche problems. This resulted in avalanche warnings and HIGH (Level 4) danger.

The likelihood of triggering PS avalanches in these areas has since decreased, but some notable D3 avalanches released post storm.  A narrow escape near Crested Butte, a very large avalanche triggered by a snowcat near Loveland Pass, and explosive triggered slides north of Berthoud Pass, and very large avalanche with an unknown trigger near Cameron Pass have us talking about if a potential DPS problem is in our future.

It is getting harder to trigger an avalanche that breaks into the weak snow near the ground in most of the forecast zones. So the Likelihood of triggering a Persistent Slab avalanche in decreasing. We have seen Very Large (D3) avalanches in the Aspen, Gunnison, North San Juan, and Front Range zones.  Most of these zones have a deep enough snowpack to produce more Very Large (D3) avalanches.  The Sawatch and Vail/Summit zones picked up less snow during the mid-December storms. Most of the avalanches in these zones have been large enough to kill you (D2), but not large enough to destroy a vehicle or timber structure (D3).We have a basal weak layer, the avalanches are getting harder to trigger, and in some zones they getting quite large. Although we have not started to warn people about DPS avalanches, some of the PS avalanches are getting larger and harder to trigger. The weather over the next couple of weeks will determine if we are just going through a scary period, or if we’ll move into a DPS cycle that lasts the rest of the season. For now, remember that we’ve seen some tricky conditions over the last few weeks and there is no indication they are over. Please read the forecast before you go out and keep in mind that this kind of Moderate (Level 2) danger includes some pretty big avalanches.

Stay safe out there and enjoy the snow!  Happy New Year!

Click here to learn more about Avalanche Problems from the USFS National Avalanche Center.

By Nick Barlow

One of the most useful resources provided on the CAIC webpage is the weather stations page (Observations > Weather Stations). Here you will find a table of hourly and archived observations from a large network of weather stations throughout Colorado, sorted by forecast zone and elevation.

The several highlighted columns report different quantities of precipitation. For SNOTEL stations, up to seven different readings are given. Below is a description of these readings, the instruments that take them, and how the data can be useful for backcountry users.

Snow Water Equivalent (SWE)

SWE is the total amount of water contained in a fixed sample of snow. More simply, it is the resulting depth of water if the entire sample melted. In this context, “sample” could mean the entire seasonal snowpack (SWE), or just new snowfall over the past 24-hours from a single storm (SWE24). Seasonal SWE is particularly useful for long-term hydrological applications, such as forecasting water supply or seasonal runoff. For example, water managers use the data to determine how much water is stored in the mountain snowpack for the warmer months ahead. This is the primary function of the SNOTEL network, and the strategic placement of stations in important water basins throughout the United States. Yet SWE is also relevant for backcountry users.

The density of water varies only slightly with temperature. By contrast, snow density varies significantly from storm to storm. The SWE calculation is a way of standardizing snowfall for use in further applications. When we think about loading weak layers in the snowpack, calculating SWE can be of great value. The data can reveal the load added to the snowpack from an individual storm.  By comparing SWE to snow depth, we can also discern whether the storm snow was dense and heavy vs. light and fluffy.

At SNOTEL stations, SWE is measured using snow pillows: large 3-meter x 3-meter bladders (steel and rubber) installed on the ground and filled with a volume of antifreeze. As snow accumulates on top of the pillow throughout the winter, instruments measure the increasing hydrostatic pressure upon the liquid. With that, the mass of the overlying snow is calculated.  Knowing the density of water allows us to calculate SWE. A snow depth measurement allows us to calculate snow density.

Measuring Snow Depth

Snow depth is perhaps the easiest quantity to measure, simply by using a ruler or avalanche probe. It is more complicated at remote weather stations with the automated measurement and logging of data.

At SNOTEL stations, an ultrasonic depth sensor mounted above the snow pillow measures the snow depth. The sensor sends a signal downward towards the ground and measures how long it takes the signal to bounce off the snow surface and return to the sensor. Knowing how fast the signal travels, a properly-calibrated sensor will give an accurate reading of snow depth.  On the weather station page, there is a field for changes in depth over a 24-hour period (Sno24), in addition to the total depth of the snowpack (SnoHt).

The ultrasonic sensor is also useful for backcountry users. Most simply, it is the only tool at a SNOTEL station that can tell you how much new powder you’ll find on any given day. However, you can glean more, and more important information from a SNOTEL site.

For one, the total depth of the snowpack can be particularly useful. A shallow snowpack can promote changes in snow structure, and create persistent weak layers. This is important information to gather before traveling into the backcountry. On a shorter time-scale, the amount the snow depth increases in a single storm is a good estimate of how much snow is available for wind transport. We can also estimate the depth of new Storm Slab or Wind Slab avalanches, and at what depth we might find the old/new snow interface in our snow pits.

Measuring Liquid Precipitation

SNOTEL stations are equipped with a precipitation gauge to measure liquid for the entire water-year. During the warmer months, rain simply falls into the gauge. The gauge then measures and logs the data automatically. Snow also falls into the same gauge during the winter months. However, sub-freezing temperatures would make any kind of liquid measurement essentially impossible. To combat this effect, SNOTEL precipitation gauges are “charged” with a volume of propylene glycol, melting the snow on contact as it falls into the gauge. The gauges also contain mineral oil, designed to sit on top of the collected liquid and prevent evaporation over time. On the weather station page, data is in 1-hour (Pcp1), 24-hour (Pcp24), and since-midnight (PcpAc) format.

For backcountry users, liquid precipitation data can also be useful. Ideally, data from this gauge would match the calculated SWE data from the snow pillow and ultrasonic sensor. This is not always the case. It’s important to recognize the differences and primary functions of each piece of equipment. Data from the liquid gauge is used for seasonal purposes. The gauge keeps measuring precipitation long after the snow melts away from the snow pillow.

However, the data can be used in conjunction with the SWE and snow depth in order to provide a more well-rounded answer to what is going at the station. An example would be for rain-on-snow events.

Snow pillows may not always capture added SWE from rainfall, as some of the liquid may channel away from the pillow. In this case, the liquid gauge is the only piece of equipment that could tell us if rain-on-snow has occurred. A simultaneous temperature reading from the SNOTEL could also reinforce our suspicions.  

Takeaway

Remember that automated SNOTEL stations exist in remote mountain locations. The stations use three different pieces of equipment to measure precipitation, and each piece has its own unique purpose for being there. Like any equipment, the gauges are prone to both random and systematic errors, and the data may not always be trustworthy.

A variety of issues can (and do) arise at SNOTEL stations. For this reason, they require continued maintenance and quality control of the data they output. This can be exceptionally difficult during the winter months, as access to many of the stations is difficult.

As backcountry users, we should analyze each piece of data individually before forming a conclusion about what has transpired. Compare the different forms of output (SWE, depth, melted liquid) and attempt to read between the lines.

Also, recognize the data is from a single point, and may not be representative of the entire area in which you’ll be traveling. Of all meteorological surface measurements, precipitation is by far the most spatially variable. You will likely find inconsistent snowfall results within different elevation bands and aspects as well. Study the data from other near-by stations; learn which stations typically receive more or less snowfall than others.

Most of all, be thankful the SNOTEL network exists. It is a wonderful tool to have at our disposal. These stations shed light into the dark and cold, providing us with vital information at just a mouse-click away.

High hopes for the new year

Everyone hoped 2021 would be a significant change from 2020. We’d see a major weather pattern change. It would finally snow. We’d put the weak, shallow snowpack behind us. Life would be good. We’d have a stable snowpack with more powder than we could ever track up. Unfortunately, no such luck. We’d start and finish January well below the 1981-2010, 30-year median snow water equivalent (SWE). The snowpack would continue to break down and weaken. We’d see over a week of clear sunny weather in the middle of the month, which was nice at the time, but would form a weak layer in the surface snow, which was not so nice after it started to snow later in the month.

A few small storms brushed through Colorado the first week of January. Although we saw a dramatic decrease in avalanche activity compared to the end of December, reports of avalanches kept flowing into the CAIC at the beginning of the New Year.

Around 8 inches of snow fell in the Northern Mountains during the first 8 days of January. In many areas, this new snow made up the entire slab for the season resting on a weak completely faceted snowpack. The new snow combined with strong winds touched off a widespread avalanche cycle in the Northern Mountains. Ninety avalanches were reported to the CAIC in the first 8 days of January in the Northern Mountains alone. Nineteen of those occurred naturally, and 32 were human triggered. Over 50 avalanches were large enough to bury, injure, or kill a person (Size D2 or larger). Backcountry travelers triggered many of these avalanches remotely from a substantial distance.

January 8 was a spectacular day for large avalanches. In one day, a group of riders remotely triggered a very large avalanche on Grouse Mountain outside of the Beaver Creek Ski Area boundary, which was caught on video. Then in two separate events, which were also both caught on video, a snowboarder was caught in a large avalanche on Loveland Pass where he deployed his avalanche airbag and ended up on the surface, and a snowmobiler near Jones Pass was enveloped in the powder cloud from a very large avalanche which he triggered frow lower in the path. He narrowly outran the slide. Both riders escaped unharmed, but they were both very close calls and could have easily resulted in burial, injury, or death.

The CAIC issued a Special Avalanche Advisory on the evening of January 8 for the Front Range and Vail and Summit County zones for the upcoming weekend. The statement warned backcountry travelers to avoid steep north, northeast, east, and southeast-facing slopes in those two zones since that is where people were triggered the bulk of the large avalanches. Nobody reported being caught in an avalanche over that weekend.

The Central Mountains picked up about 6 inches of snow from the early January storms. Fifty-four avalanches were reported to the CAIC in the Central Mountains in the first 8 days of January. Twenty-four of those were size D2 or larger. Many were remotely triggered.

The Southern Mountains fared the best for snowfall at the beginning of January, with two storms totaling a foot of snow in favored areas in the North San Juan Mountains zone. Observers reported 60 avalanches to the CAIC. Twenty-seven were D2 or larger.

And then, it wouldn’t snow again for what felt like an eternity.

It was Groundhog Day for the next ten days. Every day was clear skies, warm days, cold nights, large temperature swings between night and day, light northwesterly winds, and no precipitation.

During prolonged periods of high pressure like this, the surface snow goes through a process called near-surface faceting where large diurnal temperature swings cause the top foot (30 cm) or so to facet and weaken. This isn’t a problem when this weak layer is at the surface, but as the title of the article by Karl Birkeland in the Autumn 1998 issue of The Avalanche Review suggests, “Sometimes Today’s Great Skiing Creates Tomorrow’s Avalanche Headaches.” Nothing would prove closer to the truth at the end of January.

During the period of high pressure from January 9 to January 17, observers reported 66 avalanches. About half of those avalanches were large enough to bury or injure a person. Most broke in the weak snow near the ground. Many were unintentionally or remotely triggered.

The high-pressure ridge to our west began to break down on January 17 which opened the door for a storm to move into the Northern Mountains overnight into January 18. The Northern Mountains received 6 to 8 inches of snow in the Flat Tops, the Park Range, and the northern Front Range. This wasn’t quite enough snow to build thick slabs, but it did cap the weak near-surface faceted crystals that formed during the previous 10 days. Observers only reported a handful of avalanches from this storm in the Northern Mountains.

Snowfall tapered quickly with only a couple inches of snow in the Central Mountains, and even less in the Southern Mountains, but that was about to change.

Back to back low-pressure systems moved into the Great Basin beginning on January 21 bringing good moisture on a strong southwesterly flow. This would be the first real test of the newly formed weak layer and in areas in the Central and Southern Mountains that got the brunt of the storms, it wouldn’t hold up well.
The focus of the next series of storm stayed south, and the Northern Mountains pretty much missed out on the action with accumulations of only about 3 to 6 inches across the area. We didn’t see many avalanches during or right after this storm in the Northern Mountains.

Six to 18 inches of new snow fell in favored areas of the Central Mountains on January 23 setting off a pretty good avalanche cycle especially north and west of the town of Crested Butte. Avalanches were breaking easily on the near-surface faceted crystals buried at the new/old snow interface and easily stepping down to the ground. Observers recorded 58 avalanches in the Central Mountains from January 23 to 26. Thirty-nine of those were in the Gunnison zone.

The Southern Mountains always do well on a southwesterly flow especially areas in the South San Juan Mountains zone. Areas favored by the southwest flow picked up 8 to 12 inches of new snow with around an inch of snow water equivalent (SWE) on January 20 and then another 5 to 8 inches on January 23. By January 27, storm totals at Telluride were 27 inches with 2 inches of SWE, on Coal Bank Pass storm totals were 38 inches of snow with 2.95 SWE, on Wolf Creek Pass storm totals were 40 inches of snow with 4.3 inches of SWE, and in the La Plata Mountains storm totals were 46 inches of snow with almost 2.5 inches of SWE. Observers recorded 100 avalanches in this time period. About half of those were large enough to bury, injure, or kill a person. Two backcountry skiers were caught in avalanches in the North San Juan Mountains zone on January 24, one near the town of Ophir and another near Red Mountain Pass. Both escaped unharmed.

The final storm in January arrived just before the end of the month on January 30 and lasted through January 31.

Light snowfall started on January 30 in the Northern Mountains, but the snow really didn’t start to accumulate until the winds shifted to the northwest on January 31. Two day snow totals were about a foot in the Steamboat and Flat Tops zone, 8 inches in the Front Range zone, and 12 inches from Vail to Breckenridge in the Vail and Summit County zone. Between January 27 and January 31 observers reported almost 50 avalanches in the Northern Mountains.

Favored areas in the Central Mountains received 15 to 30 inches of snow out of this storm with the highest amounts northwest of Crested Butte into the southwest corner of the Aspen zone. About a foot of snow was reported on the Grand Mesa. Other areas to the east generally received 8 to 10 inches of snow with decreasing amounts in the northern Sawatch zone. Observers in the Central Mountains reported 229 avalanches between January 27 and 31 with 120 avalanches large enough to bury, injure or kill a person. Most, 93, of these large avalanches were in the Gunnison zone.

The Southern Mountains got another good dose of snow out of this storm on January 30. The North San Juan Mountains zone generally picked up 7 inches of new snow with strong northwesterly winds behind the front. Areas in the South San Juan Mountains zone picked up about 10 inches of snow. Observers reported just over 100 avalanches from January 27 to 31 about half of those were large enough to bury a person (Destructive size 2 or larger).

Despite the strong finish in January we still ended up well below the median snowfall for January. Observers reported a total of 856 avalanches to the CAIC during the month. Almost 200 avalanches were human triggered. Amazingly only 8 people were caught in avalanches and fortunately nobody was killed in an avalanche accident.

The avalanche rose shows the total number of avalanches from January 1 to January 31 classified by avalanche trigger type. The rings show above treeline near the center near treeline in the middle and below treeline at the edge. Wedges show slope aspect with north at the top. The filtered row shows the number of avalanches that were large enough to bury or injure a person (Size D2 or larger) for each trigger type. The numbers indicate the total number of D2 or larger avalanches on each aspect at each elevation.

The weak layer that formed during the high-pressure in the middle of the month is still plaguing us into February and there aren’t any signs of avalanches letting up on this layer.

January tried to turn the corner, but just couldn’t make the transition.

by Brian Lazar

Our first reported natural avalanche of the 2020-2021 season was associated with a healthy early September snow storm. After this single, small loose-snow avalanche in the Sangre de Cristo Range, the snow that fell in September almost completely melted away. A small storm in the second week of October added a little more to the snow cover, but our seasonal snowpack didn’t really begin to develop until we received a storm on October 24 to 26. This storm deposited 6 to 10 inches of snow across most mountain areas, with a little more in a few localized areas. Post-storm winds built stiffer slabs along ridgelines, and we closed out the month of October with the first report of a skier-triggered avalanche for the season near Breckenridge.

November had three storm events, and each produced an uptick in avalanche activity. The CAIC recorded 141 avalanches during the month, though only four of them were large enough to bury a person. Despite few areas with enough coverage for on-snow travel, seven people were caught in avalanches.

The first week of the month was dry and sunny. This melted the October snowfall on all but northerly-facing slopes at higher elevations. The snow that survived grew weak and faceted before the first storm arrived on November 7.

The first storm dropped 6 to 8 inches of dense snow across the Northern Mountains. This wasn’t quite enough to obscure the ground cover on most slopes, and we didn’t record any avalanche activity across the Northern Mountains region.

The Central Mountains picked up 6 to 15 inches of snow, favoring areas near Independence and Schofield Passes. With Highway 82 over Independence Pass still open, people had relatively easy access to high-elevation slopes. Three people triggered and were caught in small avalanches in Mountain Boy Basin over a two-day period. We recorded several small natural and rider-triggered slab avalanches across the rest of the Central Mountains.

The Southern Mountains were the clear winner from this first November storm, picking up 1 to 3 feet of snow between November 7 and 9. Coal Bank and Wolf Creek Passes received 4 to 5 inches of snow water equivalent (SWE). This storm helped to build the snowpack in the Southern Mountains faster than in the rest of the state, and this difference still remained significant through the end of the month. Although triggered avalanches were limited, we did record several skier-triggered avalanches near Red Mountain Pass and around Silverton.

After a four-day dry spell, the second storm of the month arrived November 13. This was a fast-moving storm that favored the Northern Mountains and was more notable for ferocious winds rather than ample precipitation. Remote weather stations recorded wind gusts approaching 100 mph statewide, and this event left most windward slopes scoured to the ground with stiff and discontinuous slabs plastered onto lee slopes. This event produced the distribution of our Persistent Slab avalanche problem for weeks to come, with stiff slabs most prominent on near and above-treeline, northerly and east-facing slopes.

The Northern Mountains picked up 6 to 12 inches of snow, and we recorded a dozen small slab avalanches between November 13 and 17, including a close call on Berthoud Pass on November 15. Fortunately the rider who triggered this avalanche was able to ride off the slab and avoid being caught up in the moving debris.

The Central Mountains generally received 3 to 6 inches of snow with areas near Crested Butte getting as much as 10 inches. This modest load spurred a bit of avalanche activity, mostly confined to small avalanches triggered by ski patrols using explosives. A notable skier-triggered avalanche in the Sawatch Range on November 13 provided a great illustration of our developing slab-over-persistent weak layer concern.

The Southern Mountains largely missed out on this mid-month storm, and only picked up a few inches of snowfall. They did not miss out on the wind, which redistributed the snow cover like the other mountain regions.

The last storm of the month arrived just prior to Thanksgiving Day. This one brought heavy snow to the Southern Mountains, including a nice upslope snow event in the Uncompahgre Gorge, and moderate snowfall further north. This spurred the most pronounced uptick in avalanche activity of the season with dozens of reported avalanches during and immediately following the storm. Again, all but one of these were small (less than D2 in size).

The Northern and Central Mountains picked up around 5 to 8 inches of snow in most places between November 22 and 25. We immediately saw an uptick in avalanche activity. Most of these slides were small, but a rider triggered one of the larger avalanches of the season near Berthoud Pass on November 25. On that same day, a skier triggered a small avalanche near Montezuma and took a short ride before arresting himself on the bed surface.

The Southern Mountains did the best from this storm arriving with warm southwest flow. The storm ended with cold air and just the right wind direction to generate more than a foot of snow on the north side of Red Mountain Pass. Avalanche activity perked up as it did elsewhere, and the day before Thanksgiving (November 25) turned out to be an active day in the Southern Mountains as well. A skier was caught and carried in a small avalanche in the Grandad Couloir near Red Mountain Pass. The skier was able to self arrest on the bed surface after getting knocked over, but lost one ski and one pole. Nearby, another skier triggered a soft slab avalanche and was able to ski out of the moving debris before being taken for a ride.

We ended the month with cold, clear conditions and the faceting process kicking into high gear. Small avalanches continued to trickle in through the end of the month, but there were no more reports of people being caught. Snowpack was below 30-year normal SWE, except for the Upper Rio Grande Basin, which still held ample snowpack from the nearly 5 inches of SWE it picked up in the first storm of the month.

The forecast going into December called for above average temperatures and below average precipitation.

By Spencer Logan

March has been an exceptional month in Colorado the last couple years. In March 2019, there was an incredibly widespread and destructive avalanche cycle. Avalanches ran larger than they have in 100 or more years. In March 2020, there was a widespread global pandemic. A virus had a larger global impact than any have in 100 or more years. That had little impact on avalanches, but did have a huge impact on Colorado communities and outdoor recreation. The human impacts of the pandemic arrived as avalanche conditions changed, and the confluence led to an interesting series of avalanche involvements and discussions about backcountry travel and rescuer’s risk.

March began with a large north to south difference in Snow Water Equivalent (SWE). Many SNOTEL sites in the Northern Mountains began the month with 150 to 200% of median (1981-2010) SWE. The Central Mountains started near or above the median, while most sites in the Southern Mountains were near or below median SWE. Snowfall through March favored the Southern Mountains, and reduced these disparities. All mountain regions were near or above median SWE by the end of month.

The CAIC recorded 716 avalanches in March. Thirty percent of these avalanches occurred in the Gunnison Zone, and 20% in the North San Juan Zone. Two hundred and forty, or 33% of the avalanches, were human-triggered.

The CAIC documented 25 people caught in 23 separate avalanches throughout the month. Seventeen of the incidents occurred in the North San Juan zone, and thirteen of the 17 occurred in the second half of the month. Two backcountry riders were seriously injured, requiring Search and Rescue assistance against the backdrop of the coronavirus pandemic. Despite the large number of involvements, only those two riders were seriously injured and there were no fatal avalanche accidents.

Across the Northern Mountains,the first half of March could be characterized as warm and dry. Daytime temperatures climbed above freezing almost every day. There were a few dashes of snow, but it was not until March 20 that winter returned. Calendar spring started with a good strom, bringing a foot or more of snow and an inch or two of SWE. Winds were strong and gusty during and after the storm.

Persistent weak layers remained an issue throughout the month. Slabs stacked on top of layers of near surface facets, facet-crust combinations, and basal depth hoar. Following any of the snowfall events, winds drifted snow into touchy slabs. By the end of March, low elevations and sunny slopes began the transition to a warm surface snow. Wet loose avalanches became increasingly frequent.

On March 25, two backcountry snowboarders triggered a small avalanche in wind-loaded snow on a west facing slope above the Eisenhower Johnson Memorial Tunnels. As the avalanche ran downhill, it broke into deeper weak layers and eventually to the ground. This left debris piles 20 feet deep over the Tunnel access roads.

The Central Mountains fell in the middle of the statewide north-south gradient, and also had a west to east gradient in snowfall and avalanche activity. In the east and west, the Sawatch and Grand Mesa zones, respectively, had a relatively dry month with little avalanche activity. By the middle of the month, low elevations and sunny slopes were well on the way through the transition to a spring snowpack.

After a storm in the first week of the month, warm and dry weather dominated through March 20 in the Gunnison and Aspen zones. Small wet loose avalanches were common. Melt-freeze crusts formed on many slopes, sandwiching several thin layers of faceted snow. Snowfall began on March 20, and quickly produced a cycle of large avalanches followed by another storm and avalanche cycle to close out the month. Despite the number of avalanches recorded, there were no close calls with backcountry travelers reported. Low elevation, wet-loose avalanches did run onto county roads with minor impacts in the Aspen area.

In the San Juan Mountains, small storms at the beginning of March buried weak snow that developed in February. An emerging Persistent Slab avalanche problem began to take shape but overall the slab was shallow and not heavy enough to overload weak layers. Yet.

As early as March 2 the CAIC documented a skier-triggered slide in Bear Creek near Telluride that failed on the February near-surface facets. With each storm, the slab got slightly bigger and avalanches began to increase from D1’s to D2’s. On March 9, an experienced avalanche worker triggered an avalanche near Wolf Creek Pass, was caught, and buried to his waist. By March 13 the slab was big enough to push many northwest through northeast-facing slopes close to the tipping point and riders began triggering slides at all elevations large enough to bury, injure or kill.

On March 19 snowfall began, and several feet of snow would accumulate over the next several days. Moderate southwest wind accompanied the storms. Stability slowly decreased as the snow fell, and there were both natural and human triggered slides on deeper weak layers.This increase in avalanche danger coincided with the sugre of backcountry use after ski areas were closed to reduce the spread of the coronavirus. Many riders were caught off guard by this rising avalanche hazard after a relatively stable mid-winter period. Over half of the 146 avalanches reported occurred in the 11 day period of March 13 to 24.

Wind followed the snowfall and triggered a natural avalanche cycle with some of the largest avalanches of the season (2.5 and 3 on the Destructive Scale on March 26). On March 20, there were three close calls in Ophir. In one of the avalanches, both members of the party were partly buried; one of them with only one arm free allowing her to dig out her face and clear her airway. On March 24 a rider was seriously injured after an avalanche slammed him into a tree. A very speedy response by other backcountry groups, Ophir residents, and Search and Rescue saved his life. On March 31, a backcountry tourer was ascending when he triggered an avalanche. He, too, was slammed into a tree and seriously injured. Search and Rescue evacuated the tourer.

While not the only rescues that Search and Rescue groups responded to, the avalanche incidents received lots of attention from the news media. The rescues highlighted the need for SAR volunteers to take additional precautions to minimize coronavirus exposure. The incidents also highlighted the increased need for backcountry travelers to consider their potential impacts on others. The CAIC focuses on avalanches, and encourages backcountry tourers to consider the consequences of an avalanche. But with increased backcountry use and a rapidly changing societal response to the coronavirus, avalanches were just a portion of a larger discussion of risk and exposure.

By Jason Konigsberg

Snow coverage in Colorado was fairly evenly distributed by the end of January. All Colorado river basins were at or above 100% of the normal median for Snow Water Equivalent (SWE). This changed in February. Persistent northwest flow brought consistent snowfall to the Northern Mountains and parts of the Central Mountains. SWE increases during February were 200% of the normal median for numerous Snotel sites in the Northern Mountains. The Sangre de Cristo range and Red Mountain Pass stayed close to 100% of monthly SWE increases while other areas of the Southern Mountains saw a very dry month.

The CAIC recorded 862 avalanches during the month, 122 of which were triggered by people. Eleven people were caught in avalanches, three partially buried, and tragically two people were fully buried and killed.

The first few days of February started warm and dry. The avalanche danger was Moderate (Level 2 of 5) in all ten zones on February 1 and the primary avalanche concern was triggering a small to large Persistent Slab avalanche. February 2 was the warmest day of the month and many mountain locations saw temperatures break the 40 F mark. Fremont Pass (11,400 ft) recorded a high temperature of 43 F. Schofield Pass (10,701 ft) a high of 47 F and Wolf Creek Pass (11,800 ft) a high temperature of 36 F. As temperatures subsequently cooled off, a crust formed on east through south-facing slopes. Plummeting temperatures on February 4 and 5 quickly faceted the snow around this crust. This crust-facet combination would become a major problem with additional loading.

The next loading event started on February 6. An Atmospheric River riding over a high-pressure system in the Pacific took aim at Colorado. The CAIC issued an Avalanche Warning for six zones in the Northern and Central Mountains on February 6, which continued through February 8. A period of intense snowfall began on February 6 and lasted through the evening of February 7. The northwesterly storm track favored the Northern Mountains and parts of the Central Mountains. This storm was one of the most intense 48-hour periods in recent memory. The Columbine Snotel, on Rabbit Ears Pass, recorded a 2.9” increase in SWE in 24 hours. This was the biggest 24 hour SWE increase at this Snotel since the site was installed in 1986. Other notable SWE increases included Copper Mountain and Independence Pass Snotels with a three-day increase of 2.6” and 2.5” respectively. These 3-day numbers were also a Snotel data record. Although this storm largely missed most of the Southern Mountains, portions of the North San Juan zone still picked up healthy snow amounts. Storm totals for Red Mountain Pass were about 2 inches of SWE, around 3 feet of snow.

As expected, we saw numerous avalanches during the storm associated with periods of high-precipitation intensity. As the storm cleared on February 8, it seemed that a lot of the evidence of natural avalanches was filled in by winds, obscuring the true extent of this avalanche cycle. Slopes that did not avalanche were left with a new and strong slab of snow resting on old weak layers. In some cases the 2 to 4 feet thick slab lay above both the weak layer that formed in early February and basal facets, or depth hoar, from October. Following the storm numerous avalanches broke on these weak layers in the Northern Mountains and the Sawatch and Gunnison zones.

CDOT mitigation efforts along I-70 and near Berthoud Pass on February 11 triggered a large avalanche in the Widow Maker slide path near Arapahoe Basin that buried US-6. Mitigation work also triggered another large avalanche in the Campground slide path near Berthoud Pass. This slide path put avalanche debris on US-40 for the first time since 1950. On February 13 CAIC and CDOT conducted helicopter mitigation work in Tenmile Canyon. Numerous large avalanches ran with powder clouds dusting I-70.

Northwest flow continued to generate snow through the middle of February for the northern half of Colorado. Consistent snowfall and several strong wind events led to spikes in avalanche activity. One of the most notable events occurred around February 14, causing another uptick in avalanche activity.

On February 15 , three motorized snowbikers north of Vail triggered a hard slab avalanche. All three riders were caught in the avalanche and two were fully buried and killed. This was the third and fourth avalanche fatality in Colorado this season. The avalanche likely failed on an old layer of faceted snow about three feet below the surface. This was most likely the weak layer that formed in early February during warm weather followed by very cold temperatures.

Another round of snow hit the Northern Mountains and parts of the Central Mountains on February 23 and 24. An intense band of snow set up in a line from Leadville to Breckenridge on the morning of the 23. Areas underneath this band saw 2 inch-per-hour snowfall rates with 8 to 10 inches in 5 hours. There wasn’t much wind during the snowfall and although the snow fell fast and furious, few avalanches were reported. This changed overnight on the 24 as wind increased dramatically from the northwest. The intense loading resulted in numerous natural avalanches. The most widespread activity was noted in the Sawatch Range but the largest and most notable avalanches were observed near Peak 1 in the Tenmile Range. The Peak 1 avalanche looked to be the largest avalanche in Colorado this season.


For the month of February, the Steamboat and Flat Tops zone had a lower avalanche danger than the other forecast zones in the Northern Mountains. The Steamboat and Flat Tops zone had a deeper and stronger snowpack at the start of the month. The early February storm produced abundant snowfall across the zone, but with a strong snowpack most of the avalanches were small. There were no reports of avalanches breaking on deeper weak layers during the storm or for the rest of the month. The CAIC rated the avalanche danger as Low (Level 1 of 5) for eleven days during the month. Increases in the danger were caused by precipitation and wind events, and associated new snow avalanche problems.

February was an active month for avalanches in the rest of the Northern Mountains and part of the Central Mountains. The Front Range, Vail and Summit County, Sawatch and Gunnison zones had similar avalanche danger ratings and avalanche problems most of the month.

Although the avalanche danger ratings in the Aspen zone were similar to the more active zones, there was much less avalanche activity. The number of avalanches reported decreased faster than in adjacent zones after the big February storm, and the last large avalanche in the Aspen zone was on February 8.

In the Southern Mountains, the avalanche danger was generally lower in February than it was in January. The San Juan Mountain zones went to Low danger for the first time this season on February 2. For the month, the North San Juan zone and the South San Juan zone were at Low danger 9 and 12 days respectively. Any days of higher danger were associated with small snowfall amounts coupled with wind-drifting, sometimes activating shallowly buried weak layers.

By the end of February the water content of the snowpack was above or near the normal median for most areas. The southwest corner of the state dropped below the long term median. In the deeper snowpack areas, weak layers improved and there were no reports of avalanches breaking near the ground for the last four days of February. The Southern Mountains ended the month with a shallower and weaker snowpack than on February 1. Although sunny slopes were beginning to transition to a springtime regime, the snowpack on shady slopes lost strength.

by Mike Cooperstein

The year ended with average to above average snowfall for the month of December across Colorado. Five storms during the month pushed the Snow Water Equivalent (SWE) to over 100% of the long-term median across all of Colorado’s river basins. The Southern Mountains received the most snowfall in December with areas around Wolf Creek Pass picking up almost 90 inches of new snow in the month of December alone. The new snow and periods of wind created a stiff slab over a weak layer of depth hoar near the ground and we started to see large natural and human-triggered avalanches breaking at the ground. The CAIC recorded 547 avalanches in December. Eighty-three of those avalanches were human triggered. The CAIC recorded sixteen riders that were caught in avalanches. Tragically, one of those avalanches resulted in a fatal avalanche accident. This was the first person killed in an avalanche in Colorado during the 2019-2020 season.

Five storms in the month of December 2019 brought us to above average snow and water for the season. This figure shows the basin wide percent of normal (percent of median from 1981 to 2010) snow water equivalent (SWE) across Colorado at the beginning of January.
December began with a few days of high-pressure, clear skies, and dry conditions. The next two weeks were a stormy period across Colorado with three storms hitting almost back to back to back from December 3 to December 16. Many areas in the Northern Mountains received 30 inches of snowfall in those 13 days. Breckenridge Ski Area received 43 inches of snowfall in the 3 days period from December 13 through December 16. Favored areas in the Central Mountains received around 2 feet of snowfall from December 3 to December 8 and then another 2 feet of snowfall from December 14 to December 16. Areas in the Southern Mountains received almost 40 inches of new snow as well in those 13 days with Wolf Creek Pass getting hit with 20 inches of snow in a 12-hour period on the night of December 16.
All of the new snow spurred a widespread avalanche cycle. Two hundred and ninety-five natural and fifty-five human triggered avalanches, large enough to kill or injure a person were reported to the CAIC in the first 16 days of the month.

	Natural Avalanches	Human-Triggered Avalanches
Northern Mountains	44	26
Central Mountains	191	16
Southern Mountains	60	13

This table shows the distribution of natural and human triggered avalanches large enough to kill or injure a person (D2 or larger) across Colorado from December 1 to December 16, 2019.
On December 8, a backcountry skier was caught, buried, and unfortunately killed by one of these large human-triggered avalanches. The accident occured on the Diamond Peaks in the Cameron Pass area of the Front Range zone. Many of these large avalanches were remotely triggered, which illustrated unstable the the threat from our Persistent Slab avalanche problem. Despite all of the new snow, the snowpack remained relatively thin across most of the state and most of these avalanches broke at the ground.

On December 1, 2019, a snowmobiler remotely triggered this avalanche in the Rollins Pass area in the Front Range zone. Observers reported cracking and collapsing and many remotely-triggered avalanches to the CAIC in the first few weeks of December.

A skier triggered this avalanche on Berthoud Pass, in the Front Range zone, on December 11, 2019.

This photo shows a remotely-triggered avalanche in the Vail and Summit County zone on December 12, 2019.

From December 17 until about December 23 a period of high pressure brought dry conditions with clear skies and unseasonably warm temperatures. Temperatures rose well above freezing in many areas. This built sun crusts on southerly-facing slopes and left weak, faceted crystals on the snow surface on north and east-facing slopes. These would become the weak layers for avalanches toward the end of the month. Riders continued to trigger avalanches that broke at the ground during this prolonged dry spell.

A snowmobiler remotely triggered this avalanche in the Never Summer Range, Front Range zone, on December 17, 2019. He was farther away than where this picture was taken when he triggered the avalanche.

A snowboarder unintentionally triggered this large avalanche in the Loveland Pass area on the border of the Front Range and Vail and Summit County zones on December 19, 2019.
Just before Christmas another storm moved over Colorado. On December 25 and 26 areas in the Southern and Central Mountains as well as the Vail and Summit County zone accumulated 12 to 16 inches of new snow. The Steamboat and Flat Tops zone and Front Range zone picked up 3 to 8 inches of snow. This snow fell on a weak snow surface in many areas. We continued to receive reports of large natural avalanches over Christmas; however, we were seeing many fewer avalanches break at the ground and many more avalanches break at the interface between the new and old snow.

A natural avalanche in the Wemuniche Wilderness in the South San Juan zone, December 26, 2019.
The final snow storm of the decade occurred from December 27 to December 29. Snowfall favored the Southern Mountains with up to 20 inches near Wolf Creek Pass and diminishing totals as you headed north. There was still some avalanche activity breaking near the ground, but most avalanches released in storm or wind-drifted snow. Avalanches continued to break on these mid-pack weak layers for some time to come. In the deeper snowpack areas forecasters were becoming less concerned about the deeper buried weak layers. In the thin snowpack areas these basal weak layers continued to plague us every time we got big storms. We finished December the same way as we started, with clear skies and cold temperatures.

The 2019-2020 season began with storms in the second week of October. The month closed with several more storms continuing on and off through the end of the month. Observers reported “excellent for October ” conditions. SNOTEL stations in the Northern and Central Mountains reported far more than typical amounts of precipitation, but “more than normal” in October still translated to rather thin snow cover with just a couple inches of snow-water equivalent on the ground. The CAIC recorded six small natural avalanches in the Northern and Central Mountains. A foot or less of snow fell in the Southern Mountains, enough to offer a glimpse of winter but not much snowy recreational opportunities.

First reported natural avalanche of the 2019-20 season. This soft slab avalanche released on a northeast-facing slope on Independence Pass around October 24 after receiving around a foot of snow in the previous week.

November began with almost three weeks of dry, mild weather. The snow that lasted through the dry spell on high-elevation north and east-facing slopes faceted into well developed depth hoar. This became the poor foundation upon which we would build the rest of the season’s snowpack. Thin crusts formed on sunny slopes that did not melt back to bare ground, and widespread surface hoar formed on the snowpack surface. Snowpack characteristics were similar statewide, other than more melting in the San Juan Mountains, and some isolated drifts of dense snow in addition to the depth hoar and thin crusts in the Northern Mountains.

Snowfall starting November 20 brought an end to the dry weather, and a corresponding uptick in avalanche activity across the state. Most avalanches ran on higher-elevation north and east-facing slopes and most broke into the depth hoar. With a shallow snowpack most avalanches were small, but the pattern was a sign of things to come. A series of storms would close out the month starting just prior to Thanksgiving. The snowpack failed this second test and we saw another avalanche cycle. We also started to see some variations across the regions.

This is an example of a shooting crack from the Aspen zone on November 22, 2019. Obvious signs of instability like these were widespread around the state when snowfall returned around November 20, ending our November dry spell.

In the Southern Mountains observers found shooting cracks, collapses, and a natural avalanche cycle that occurred the day after Thanksgiving. That prompted the first Avalanche Warning of the season on November 29. On November 30, two snowshoers triggered and were caught in an avalanche east of Red Mountain Pass.

This avalanche was remotely triggered from flat terrain on Red Mountain Pass on the last day of November. Avalanches like these gave us a good indication of how December would unfold when we got more loading events.

Snowfall from storms around Thanksgiving Day overloaded portions of the Central Mountains. The result was a cycle of small to large natural and human-triggered avalanches in the Gunnison and Aspen zones. The month ended with Considerable (Level 3 of 5) danger ratings and backcountry forecasts discussing the potential for people to trigger large avalanches near and above treeline on north through east aspects, especially around terrain features with wind-drifted snow.

In the Northern Mountains, a strong upslope storm developed just before Thanksgiving Day. A backcountry skier was caught and carried in a small avalanche while skinning uphill in Jones Pass on November 22. A backcountry skier was buried with just an arm above the snow near Searle Pass on November 28. A swift companion rescue prevented a tragic outcome. As snow continued to accumulate, avalanche size increased with a few large avalanches reported on November 29 and 30.

This small avalanche buried a person with only one arm sticking out of the snow on Thanksgiving Day. The other two people in the group quickly rescued the victim. The storms around Thanksgiving Day caused avalanche danger to rise and a corresponding increase in avalanche activity.

We ended the month on the way to better coverage, but with poor snowpack structure and weak layers ranging from depth hoar, to crust-facet combinations, to buried surface hoar. We were primed for more avalanche activity as soon as we got our next loading event.

Blase Reardon

On January 17th, 2014, a pair of riders triggered a large avalanche on a steep, near-treeline slope in the backcountry behind Snowmass Ski Resort. The slope had previously been nicknamed “Mr. Magoo’s” after a ski patroller who sometimes acted like the near-sighted cartoon character. The riders escaped unhurt, despite an ugly terrain trap below. An hour later, the resort’s snow safety director watched a solo skier turn down the same slope and trigger a second slide adjacent to the first. He met the solo skier as he returned to the resort and asked him whether he’d seen the first slide—or the larger natural avalanche just up the drainage at the same aspect and elevation. The solo skier replied, “It’s okay; I have skied Silverton and I skied the path a couple of years ago.”

The slope where the January 17th incidents occurred is steeper than 35 degrees and faces southeast. On that day, it was blanketed with a foot-thick slab formed by a recent storm and subsequent cross-loading; the slab sat on a thin, persistent weak layer. It was a slope that closely fit a pattern of recent avalanche activity and that was highlighted in the CAIC forecast as the kind of slope where people were most likely to trigger slides. With the danger rated as Considerable, skiing that slope on that day was a risky proposition, especially alone and with a fresh slide visible.

The solo skier didn’t answer the question posed to him – did he see the other slide and, implicitly, was he concerned about avalanche danger on the slope? Indeed, he seemed to answer a different question altogether, one centered on skiing rather than avalanche conditions. Perhaps standing at the top of Mr. Magoo’s he asked himself, “Can I ski a slope like this?” And his answer seems to have been “Yes, because I’ve skied slopes this steep before. I’ve even skied this slope before.”

According to Nobel-prize winner Daniel Kahneman, substitution like this is a nearly automatic cognitive response to complex, irregular environments. Our brains produce what Kahneman calls “off-the-shelf answers” to difficult problems by answering simpler, more familiar questions. It’s a sub-conscious process, and it provides solutions that leave us feeling very confident in our assessments and choices. Assessing the risk of triggering a slide on a steep slope covered with new snow is a complex task, fraught with uncertainty. Faced with that, our brains quickly default to questions with simpler answers, like “Can I ski this slope without falling?” or “Will the skiing be as good as it looks?”

Marketing provides numerous everyday examples of this pernicious tendency. When faced with a question like “Is this the best pair of skis for me to buy?” we often answer a question more like “Do I like this brand of skis?” or “Do I like the graphics?” In situations like these, substitution often provides adequate answers, because the alternatives aren’t that different and the consequences of not answering the initial question aren’t severe. And substitution has the advantages of saving us mental energy and time. Once we’ve substituted a simple, seemingly coherent answer to a complex question, we can confidently summon numerous arguments supporting our choice without recognizing the substitution.

That leads us back to Mr. Magoo, the cartoon character referenced in the slope’s nickname. Mr. Magoo stubbornly refuses to recognize his near-sightedness. He doesn’t have to, because situations always work out for him. Magoo mistakes an airport for a movie theater, takes a seat on a departing plane—”It’s like I can feel the plane taking off!”—wanders around on the wings, unknowingly leads the police to a bank robber, and when the plane lands, tells the flight attendant he really enjoyed the film. The tension in the Mr. Magoo cartoons derives from seeing how lucky the character can get yet be oblivious to the dangers he’s facing, thanks to his near-sightedness . They’re funny because we know his luck will never run out.

We can all be Mr. Magoos in the backcountry. When nothing bad happens, it’s easy to finish a day of skiing or riding in avalanche terrain feeling confident we made good choices. So it’s easy to take the wrong lessons from our experiences. We’re sure we really liked the movie, unaware of how close we came to falling off the wing. The three riders involved on the slides on January 17th might easily conclude that they judged conditions correctly. More correctly even than the forecast, which called slopes like Magoo’s dangerous. None of them were hurt. The answer of “Yes, I can ski this” seemed to work, so the solo skier might be more likely to rely on it the next time he’s faced with a slope where the stability is questionable.

The winter backcountry is no cartoon, however. Substituting an easy question for the relevant one can kill our friends, our loved ones, or us. Our luck can run out. Or we may not get lucky at all. It’s what Kahneman and others have termed a “wicked environment”—an environment in which a lack of regular, reliable feedback allows us to develop habits and patterns based on faulty correlations, or luck.

So, what’s the alternative, given our brain’s hardwired proclivity for substitution and the wicked nature of the backcountry? How do we keep from being Mr. Magoo?

In previous section of this article, I noted that the winter backcountry is an instance of what Nobel-Prize winning researcher Daniel Kahneman and others describe as a “wicked environment” for developing expertise. In part, that’s because expertise in the backcountry is a collection of skills. We have to master the individual elements—technical skiing and riding skills, route-finding, and stability assessment among them—while simultaneously learning which items in the set to prioritize and apply in a given situation. It’s also because in the winter backcountry, we don’t get much immediate, consistent feedback on our decisions and actions. We rarely know how close we are to triggering a slope, so it’s easy to develop habits and patterns based on faulty correlations, or luck.

A real-world example of the rarity of immediate feedback in avalanche terrain surfaced a few years ago, in a video posted on YouTube that’s since been pulled. It showed a skier finishing a run on Puckerface, a steep slope near Jackson Hole Mountain Resort. The soundtrack includes lots of whooping. Then a title card appears, reading “Second Run. 10 minutes later.” A snowboarder starts down the same face, and makes a hard first turn. The entire slope fractures several feet deep, and slides. The snowboarder claws into the bed surface and stops. The camera shakes and jerks, accompanied by lots of cursing. The snowboarder walks away on the ridge. The video shows the slide a second time, in slow motion.

Let’s put ourselves in the boots of the first rider on Puckerface on January 2, 2012. We choose to ride the  slope for some reason—maybe a well-considered assessment of stability, maybe by substituting a question that’s easier to answer, like whether there’s enough sun on the face for good video. When it doesn’t slide, we conclude our rationale was correct. Given enough similar experiences, we could start to feel very confident in our skills. But the slide triggered by the second rider reveals a more accurate conclusion: we got lucky. And instead of developing skills, we might just be getting lucky, a lot.

The image above also shows Puckerface on an early-winter day, this time nearly two years later, on Dec. 26, 2013. On this day, a rider wasn’t so fortunate; he was killed in the slide visible in the image. That’s the potential penalty for substitution, inadvertently relying on luck, or just plain making a mistake. Each day in avalanche terrain, each run or route we chose, is unique and novel; we have incomplete or ambiguous data, we get one chance, and the cost for choosing badly can be fatal.

An alternative to relying on luck is expert intuition—distinguishing familiar cues in a new situation and choosing an appropriate response. As Kahneman notes, “Expert intuition strikes us as magical, but it is not…[It] is nothing more and nothing less than recognition.” It’s Mr. Magoo with eyeglasses, a prescription that lets him recognize an airplane instead of confusing it for a movie theater. In his classic essay “The Ascending Spiral”, pioneering snow scientist Ed LaChapelle echoes that point; intuition “is not some sort of extra-sensory perception.” He describes it as a “lifetime accumulation” of observations about snow, avalanches and weather. That doesn’t just happen, because the backcountry is a wicked environment. We help develop it by adopting simple habits that, over time, make the backcountry environment more regular and expand the base of stored cues necessary for expert recognition.

Below are examples of practices  that can improve the quality of our observations, our communication, and the feedback for our decisions.

It’s all about the up: Most—at least two thirds—of our time in the backcountry is spent going up. It’s our best opportunity for observing and communicating. It’s also when most miscommunications and mistakes occur. Set a low-angle, meanderthal skin track that takes advantage of the terrain to investigate different aspects and slope angles, and that allows relaxed discussions of your observations without having to stop. Steep skin tracks make it hard to see much beyond your ski tips, and even if you do notice something important, it’s hard to communicate it when you’re anaerobic. If you’re breaking trail and can’t hear the group behind you talking, your track is too steep for easy observations and communication.

Give it a rest: Take breaks at decision points. Fiddling with your clothes or gear randomly just slows you down yet provides little information about snow conditions or route choices. Stopping to drink, eat and layer up when you’re faced with a decision is productive; it allows you to look around when you’re comfortable and talk about what you see. More often than not, you’ll pick up nuances in the terrain that you didn’t see while moving and out of breath—as will your partners. And you’ll make better decisions when your brain isn’t starved for oxygen or nutrition. Pace your group so you’re moving steadily and don’t feel rushed when you stop at decision points.
You are not the Captain now: Encourage feedback within your group. You’re looking for ideas that can save your ass, not aiming for agreement. It helps to rely on questions rather than declarations. “Does that side of the slope look wind-loaded?” instead of “Most of the slope isn’t wind-loaded.” Listen for contrarian opinions rather than trying to silence a squeaky wheel. Acknowledge that anyone in the group has veto power.

Write it down: Keep a field notebook or submit observations to your local avalanche center after each backcountry trip. It’s a sure way to notice and remember details about snow and weather conditions.. Summarizing them for a field report forces you to make sense of what you observed, to sort what’s most important from what’s irrelevant. And it gives you something besides dim memories when you’re checking impressions of past events.
Debrief: When we talk about a day in the backcountry immediately afterwards, we often focus on the highlights—the great run, the funny fall, the beautiful light or snow. You provide otherwise unavailable feedback on your decisions by including an opportunity to talk about how you did things and whether those actions put you at risk. Guides often do this formally, in afternoon meetings in which they can identify when they were most at risk during the day. A friend’s more informal approach, is to ask, “Well, did we get it done, or did we get away with it?” Find a way to expand your end-of-day conversation to more than high fives. If something nags at you a day or a week later, talk with your partners so everyone understands and learns from the experience.

Find a mentor: Years ago, I spent a day traversing a high peak in the Wasatch with a mentor when the avalanche danger was high.  It was a lesson in micro-route-finding. Near the end of the day, when it seemed we’d mostly passed the hazards, I took a few extra turns on a small slope I now recognize as a terrain trap. I looked up to see my mentor giving me a look that said, “That. Was. Dumb.” That look still floats into my consciousness when I encounter similar slopes. Though the look clearly communicated stupidity of my move, it was much more forgiving feedback than triggering the slope. Or another like it, because without that mentorship I might have gone much longer without learning to take small slopes seriously. You learn from (and with) a mentor in an iterative process, the goal of which is your becoming equally skilled and knowledgeable, perhaps more so, than your mentor. This relationship is different than that with a guide, who may pass on some useful tips but who is a leader.

Others with extensive expertise in the backcountry can offer up other practices like these, which may work better for them or better period. The point is less the specific habits than making an effort to maximize the quality of our decisions and the feedback we get for them, so we have the best chances of seeing our Mr. Magoo-like close calls and learning from them, without the too-painful learning that comes if our luck runs out.  Time in the backcountry with that kind of reflection is what leads to the lifetime of accumulation and instant recognition that Kahneman and LaChapelle identify as expertise.