Slide Science 

Montana researchers dig into avalanche mechanics

Page 3 of 4

Snowpack modeling is a growing avenue for making snow science available to those who use it on the ground—namely ski patrollers and avalanche forecasters.

"We take a digital elevation map," Adams explains, "and we digitize everything. We add vegetation, like trees, and we add snow in there and how the shadows are cast."

By calculating for a known set of variables, Adams can follow the energy transfer and subsequently see how snow might change in a way that can compromise its structural stability.

The use of models for predicting landscape conditions is widely used in fire science. Wildland fire managers use models that account for wind, humidity and fuel type to predict how fire moves across a landscape. Adams hopes snowpack modeling is headed in the same direction.

"Running these models you can actually see what's happening, you can see the temperatures changing across the snow," Adams says.

This kind of technology has the potential to be very useful for avalanche forecasters.

Technology aside, Adams' intricate understanding of snow structure makes him somewhat of a human avalanche model.

"Once you start looking at all the conditions that can change snow, you begin to process what goes on and build them into the little computer in your head," Adams says.

That sort of processing is intrinsic to skiers with countless hours logged in the backcountry. Over time, some develop an uncalculated feel for what's going on with the snow.

•••

Steve Karkanen is another one of those human avalanche models. But in Karkanen's defense, he also uses a multitude of physical tools to do his work.

Karkanen is the director of the West Central Montana Avalanche Center, a nonprofit avalanche advisory service funded by the Forest Service and by private donations. The group is better known as Missoula Avalanche, locally famous for their avalanche awareness courses and Kettlehouse fundraisers.

click to enlarge David Walters “farms” snow in the Subzero Lab. - PHOTO BY  YOGESH SIMPSON
  • Photo by Yogesh Simpson
  • David Walters “farms” snow in the Subzero Lab.

Three forecasters prepare backcountry advisories for west-central Montana, and Karkanen brings 21 years of professional ski patroller experience to the head of the table.

"We're looking for a lot of things, not just the quality of the snow, but also its history," Karkanen says. "We're looking at what's happened with the weather the past few days and what's going to happen with the weather."

If snow is like clay, then the environment is its sculptor. Karkanen and his colleagues watch the alpine snowpacks as early as October to get an idea of how base layers are shaping up for the season. They watch the weather to gauge probable snowpack conditions. But just as importantly, the forecasters head into the backcountry, digging snow pits and physically testing snowpack stability for Missoula Avalanche's bi-weekly advisories.

The bulletins—posted every Monday and Thursday—reflect the general conditions in the backcountry ranging from down in the Bitterroot all the way north through the southern Swan and Mission mountains. Describing the variability of the snowpack over a broad area is a challenge.

"It's not easy to come up with a report at 4 or 5 in the morning when you've got multiple different types of weather in different areas of our advisory," Karkanen says.

For example, last winter's snowpack was marked by a layer of depth hoar, an unstable layer that has a sugary consistency that doesn't bind well to other layers. Think of it as the type of snow that's useless for making snowballs.

"We had up to 70 centimeters of depth hoar," Karkanen says about last season's snowpack. That layer came from a November snow dump followed by spring-like conditions without much new snowfall. The risk was recognized early on, and a mention of the depth hoar layer consistently made it into the avalanche bulletin.

Those bulletins are becoming increasingly well read. Missoula Avalanche's website received over 34,000 hits last seasona 14-percent rise in traffic over the previous winter. Karkanen says the spike is the result of more people recreating in the backcountry now than when he first started monitoring snow conditions.

With more backcountry skiers, Karkanen stresses another key component of Missoula Avalanche. He says avalanche education has become the most important part of his group's work.

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