Roaring Fork Valley avalanche conditions to worsen next week, sources say

Local avalanche conditions will likely worsen next week, with a low-pressure system expected to bring snow starting Wednesday. 

The six-to-eight inches of midweek expected snowfall will cover a weak layer that has formed amid January’s weeks-long dry spell, according to Brian Lazar, deputy director of the Colorado Avalanche Information Center. But the exact quantity of next week’s snowfall is still an estimation because the prediction is a week away, he added.

“How severe the changes are going to be really depends on how much snow we end up getting,” he said of next week. “And we’ll have a much better idea of that in the coming days.”

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Though he doesn’t yet know the extent to which the conditions will worsen, Lazar advises those who plan to go into the backcountry to study the avalanche forecast, which can be found on the Colorado Avalanche Information Center website, avalanche.state.co.us.

This month’s cold, dry weather prompted a weak surface layer — or near surface facets — to develop on the snowpack, he added. When the weak, non-cohesive snow is covered by heavier snowfall, there is higher potential for the excess weight to slip along the buried layer, causing avalanches. 

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A faceted layer is a broad category for a weak layer of snow, constituted by large snow grains with many edges. The edges make it difficult for the grains to bond to one another, creating the weak layer. 

“A weak layer would be like pouring a bunch of … diamonds into a bin,” he said. “You have a lot of air space in there, and the contact points between the individual grains are very small relative to the grain size.”

Faceted weak layers form when there is a high change in temperature through the depth of the snowpack, known as a high temperature gradient, or specifically when there is a 1 degree Celsius change over 10 centimeters of snow. This frequently happens on cold, clear nights to the top of the snowpack because the surface heats up during the day then rapidly cools, creating a difference in temperature between the upper-most layer and the snow just below the surface, which remains warmer.

January tallied 18 temperature recordings below zero degrees fahrenheit, with temperatures as low as negative 24 degrees, making for many cold, clear nights and much faceting, according to Natural Resources Conservation Service’s SNOTEL site on Independence Pass. 

The stronger macro-category is a rounded snow layer, consisting of smaller, rounder grains that bond together with greater ease. Lazar described the layer as pouring BB’s into a bin. There is less air space separating each BB, so they form a more cohesive mass and leads to stronger snow.

After the significant dry spell, the Roaring Fork Valley sits at 91% of the 30-year snowpack average, according to the National Resource Conservation Service. The valley is predicted to get up to 30% less precipitation in February, March, and April.

But this season has brought a slightly higher avalanche rate than previous years, with 535 avalanches recorded in the area, which includes much of the Roaring Fork Valley, the crest to the western side of the Elk Mountain Range, as well as the area around Sunlight Ski Resort and Marble. The state of Colorado has already seen 2,500 avalanches. 

Lazar said, however, that the higher rate was mostly due to a high natural avalanche cycle in early January and following the Thanksgiving storm cycle, which brought multiple feet of snow to the valley. He is not sure if the rate will remain higher throughout the season.

The Thanksgiving cycle caused half of the Highlands Bowl to slide before the mountain opened, said Andy Biehl, training coordinator for Highlands Ski Patrol.

The half that slid was the area that ski patrollers and volunteers hadn’t yet “boot-packed,” or stomped down to solidify, which they do during the five to six weeks before opening.

But the combination of early season bootpacking, frequent ski traffic, and avalanche mitigation by ski patrol keeps the bowl safer during the winter, according to Andrea Tupy, Highlands snow safety technician.

“In bounds terrain is totally different than backcountry, so it’s definitely a different beast,” Tupy said.