Understanding the Early Season Snowpack

The early start to the 2013 ski season kicked off with images of powder turns accompanied by stories of accidents. To date, over twelve people were reported injured or were involved in skier–triggered avalanches. Many backcountry users have observed additional natural and human triggered events. Every year, the story repeats: As the snow begins to fall there is an inevitable, and often painful, meeting of early season skier stoke with twitchy, shallow, early season snow conditions. 

Most avalanche websites from across North America are not even up and running in October and November, so it is easy for even experienced backcountry travelers to put the possibility of avalanches on a lower scale than in, say, February. Yet the low snowpack is a good time for skiers out in the field to start monitoring and understanding the effects of the early snow layers on stability in both the short and long term.

Early conditions like this year’s persistent weak layer—the one that keeps making the news across the west—provide some of the most markedly tricky and unstable snow out there, according to Utah Avalanche Center forecaster Drew Hardesty. The reports of avalanches from southern Colorado to interior British Columbia are actually fairly normal behavior for early season snowpack.

Photo compliments of Utah Avalanche Center (UAC)

Whether the increase in human involvement is due in part to more communication and information sharing in the backcountry community or to more increases in backcountry travelers in general isn’t entirely clear. What is clear is that skiers tend to let down their guard in the early season thanks to being fueled by a powder frenzy and a false sense of security from the low snowpack. 

“This time of year, skiers go up to where they find snow: at elevation, on steep aspects, and there is often windslab sitting right on weak, shallow early layers,” explains Tom Murphy, operations director at the American Institute for Avalanche Research and Education. 

Some years the early layers are more dangerous than others, and the resulting persistent weak layer stretches across the West. This weak layer is concentrated on slopes and elevations where snowfall from September and October did not melt and it formed into facets during the subsequent cold, dry spells. When buried under later snowstorms, this older, loose snow becomes an instability. Combined with low overall snow depth, this creates easily impacted trigger points that sit atop weak layers. 

“Early season avalanches may not be the size or frequency typical to later in the season, however, the consequences of getting caught can often be very serious due to exposed rocks and other hazards,” offers Dean Lords, an Idaho-based instructor of avalanche courses for ski patrollers in the Intermountain West division. “Head and body trauma are more common than fatalities due to burial when the snowpack is low,” Lords explains.

Image of depth hoar measurements courtesy of AIARE/Stefan Olson 

Bob Comey, director of the Bridger Teton Avalanche Center in western Wyoming, cautions skiers to be aware of the early snow layers from September and October—especially on shaded northerly slopes—that did not melt above 9000 feet and now exist as substantial buried depth hoar. This layer near the ground is causing problems for early season skiers who venture onto north facing slopes at elevation, which, in other words, is where the most and best snow is often found. 

“We have already had two incidents in our area where there could have easily been fatalities,” Comey notes. “This is what we call a persistent weak layer—meaning it will be an issue for a long time. Moving forward, we have to treat terrain with this layer differently, which means you should stay off it until it stops reacting,” he cautions. “That type of weakness is a tough hazard to manage.” 

According to Comey, digging a pit will only tell if this type of instability is in the area and not if it will react. Furthermore, cutting the slope is not an effective way to test the volatility of persistent weak layers. The only way to stay safe is to practice restraint and wait until the weakness dissipates, he says. 

Persistent weak layers do have to the potential of stabilizing as the season moves forward. “We hope to have multiple big storms with wind come through [the Jackson and Teton area], and if we see no activity after that on this layer, this layer may eventually become too deep to trigger easily. People can look on our website (

Photo compliments of

A recent slide in a west facing couloir of Jackson Peak. Photo compliments of Bridger Teton Avalanche Center.