A mass of heavy snow slides down a 40-degree mountain slope, hissing as it gains speed and momentum. The concrete-like mix comes to a slow stop along Highway 2 near Stevens Pass, completely blocking the road from vehicular traffic and knocking over large Douglas fir trees, upturning boulders and causing destruction in its wake. 

For skiers hoping to make it back to Seattle from a long weekend of recreation, or folks with a cabin getaway in the mountains rushing back for the work week, a road closure due to an avalanche may come as a surprise, but for a forecaster, predicting avalanches is just a part of daily life. 

National Avalanche Centers

There are 14 National Avalanche Centers in the United States. The Northwest Avalanche Center (NWAC), based in northeast Seattle, puts out a daily forecast for the public from approximately November through May, to inform anyone traveling into the backcountry in the Cascades, Olympics and Mount Hood region what the hazards are and how likely an avalanche is going to occur or be triggered. 

The deadliest avalanche in U.S. history, in fact, occurred in Washington state more than a century ago, in northeastern King County. The Wellington avalanche (formerly a small unincorporated railroad community in the Cascade Range at Stevens Pass) killed 96 people in 1910 after a severe blizzard followed by a lightning strike. King County officials say hundreds of avalanches still frequently occur in uninhabited areas in the Cascades north and south of I-90, and “people most at risk are winter enthusiasts using Stevens Pass, Snoqualmie Pass and the Crystal Mountain Ski Area near Chinook Pass.”

Challenges in predicting avalanches

Predicting avalanche danger is a difficult undertaking and requires a set of unique skills. Forecasters must know a great deal about meteorology and weather patterns, acquire knowledge of snow science and be in tune with what triggers and causes avalanches. They must also possess the ability to detach themselves from the emotional aspects of avalanches, separating their egos from the process, and rely on patterns, data and science rather than going off gut feelings or hearsay. Easier said than done. 

Robert Hahn, an avalanche forecaster for NWAC, is aware of the traps that he can get sucked into, causing him and his coworkers to predict avalanches in subjective rather than objective ways. 

“The biggest challenge that we have is group think, allowing others to influence our thoughts,” Hahn says. He describes how every day before NWAC puts out its avalanche forecast, four to five of his colleagues meet to discuss the current avalanche forecast and determine what the danger rating (on a scale of 1 to 5) should be for the following day. It is easy for him to come into the meeting with a strong opinion related to the current or upcoming rating but may get swayed by others’ judgment if there is an overwhelming consensus between his cohorts. 

In 2017, the National Avalanche Centers around the country adopted a more conceptual model than they previously had that relies on a scientific process laid out for the forecasters that helps them determine the danger based on the problems in the mountains. Despite this, it is impossible to completely take out the human factor when it comes to predicting such a dynamic and natural occurrence.

Sometimes the forecasters are simply left in the dark. “Limited observations [from the field] can lead to bad forecasts,” Hahn notes. When forecasters aren’t getting enough information by boots on the ground, be that ski patrollers, highway crews or backcountry users, they may be forced into predicting avalanches based on expectations and experience rather than hard facts. 

The avalanche rating, hazards, and minute verbiage determined and used by the forecasters in their forecasts has a huge effect on decision making for anyone traveling into or through avalanche terrain. “There are days that are really dynamic, and you have to ask the backcountry user to do more,” Hahn says. Because weather and conditions change throughout the day, the likelihood of an avalanche may increase or decrease greatly from the original forecast. For this reason, it is difficult to be certain of a forecast on days when the weather changes a lot. 

An avalanche forecaster holds a lot of responsibility. Lives are at stake when people go into risky terrain and every year people die in avalanches, especially as more and more people recreate in dangerous environments. Hahn adds: “It’s more common that we get weather forecasts wrong than make an emotional avalanche forecast,” proving that the scientific approach to the job helps forecasters make sound decisions. 

At the end of the day, traveling in avalanche terrain is dangerous, and it is on each individual to evaluate the dangers of the snowpack instead of completely relying on forecasters. After all, they are only human.