Summit avalanche danger reaches "considerable’ level |

Summit avalanche danger reaches "considerable’ level

SUMMIT COUNTY – Avalanche conditions in the northern mountains, which include Summit County, are rated “considerable,” Colorado Avalanche Information Center (CAIC) forecasters said Wednesday.

“Considerable” means natural and human-triggered slides are probable and large, deep avalanches are possible. Only “high” and “extreme” conditions are considered more dangerous.

According to forecaster Dale Atkins, backcountry travelers should be “very leery” of steep, wind-drifted slopes and gullies.

“The wise will avoid all steeper slopes,” Atkins said.

“People should also be leery of triggering steep slopes from below, especially in the northern and central mountains. A collapse at the bottom of a steep slope is kind of like pulling out the log from the bottom of the wood pile. It can release avalanches from above.”

The CAIC has received reports of 244 avalanches throughout the state since Saturday, including 159 in the southern mountains, 72 in the northern mountains and 13 in the central part of the state.

“Backcountry travelers need to use extra caution and excellent route-finding techniques,” Atkins said. “Triggered avalanches are probable in most mountain areas on slopes steeper than 30 degrees.”

A low pressure system is expected to spin moisture into the southern mountains this week, bringing light snow to the mountains. Scattered snow showers were forecast for today, dropping up to 2 inches of snow, with highs in the 20s.

“It may not take much sun to cause loose-snow releases from steep, rocky areas,” Atkins said.

“In the central mountains, it is a mixed bag. The region received less snow than the southern mountains and less wind than the northern mountains, but I suspect shallow new slabs and older, deeper weak layers still exist.”

Late winter and early springtime are prime avalanche seasons, as snow and weather conditions change.

Three factors – snowpack, weather and terrain – go into making an avalanche, said CAIC forecaster Nick Logan.

Humidity is responsible for the initial shape of snowflakes. But early season snow and temperature fluctuations melt and smooth the pointed snowflake crystals, making them less likely to bond to one another. The weight of additional snow on old snowpack also breaks down the snow crystals, making them into a compact grain.

When a new storm moves through, the snowfall doesn’t affix to the old, rotten snow, Logan said. Snowpack then awaits a trigger – be it wind, a human or sheer stress on the snowpack – to slide.

Clues that an area is prone to avalanches include previous slide paths, flag trees – those with broken, uphill branches – and cracks along the snow surface.

Backcountry enthusiasts also should pay attention near rocks, Logan said. While some might be safe refuges, snow in the area can be weak because the sun heats rocks, causing snow to rot.

Temperatures, humidity and wind also affect avalanches. Changing temperatures melt and refreeze snowpack, making it less stable.

“If the temperatures increase fast enough, they’ll destroy the bonds between the old and new layers,” Logan said. “Snow’s just like Silly Putty. If the temperatures change slowly, it’ll adjust. But if they change fast, it gets real brittle.”

Jane Stebbins can be reached at (970) 668-3998, ext. 228, or

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