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Avalanche experts demonstrate snow stability test to help determine avalanche risk

avalanche pit digging.jpg
Posted at 7:53 AM, Feb 26, 2023

Part Two of a two-part series by MTN's Matt Elwell, exploring the work of the Gallatin National Forest Avalanche Center.

BOZEMAN — Winter weather has been hitting Montana hard this year. Heavy mountain snow, strong winds, and bitter cold temperatures have been keeping avalanche forecasters on their toes regarding snow stability in Montana’s backcountry. Nationwide, the United States has seen nine avalanche deaths through Feb. 23. One of those deaths was a snowmobiler in Cooke City, Montana on New Year’s Eve. Unfortunately, there are still weak layers in the snow that are causing concern.

One of the best tools to find out if the snow is unstable is digging a pit and doing a stability test. The Gallatin National Forest Avalanche Center (GNFAC) digs down into the snow and performs stability tests in avalanche terrain every day. “As an avalanche forecaster and an avalanche center, we are giving a regional perspective” the director of GNFAC told MTN News. “We are painting the avalanche danger with a pretty thick brush.”

They cannot possibly hit every slope in an area that reaches from south of West Yellowstone to the Bridger Range. They try to hit slopes that are suspect or that people are recreating on to either test the stability or determine if the slope is becoming more, or less, stable. But you can’t solely go on that information alone if you want to stay safe. “When you go out if you are a skier or a snowmobiler, and you are heading to a specific slope and you want to know, will this specific slope avalanche or not, the onus is going to be on you to figure out if that slope is safe or not.” Chabot said.

Digging a pit and performing a stability test is really the best way to tell if snow is unstable if there is no evidence of recent avalanches. “People say, ‘oh my god, I don’t want to dig down, it’s going to take a lot of time’” Chabot said. “But it doesn’t take a lot of time.”

In a matter of 5 minutes, Chabot was able to do an avalanche assessment with what is known as an Extended Column Test (ECT). That included digging a pit, isolating a 90 cm by 30 cm rectangle of snow, and performing a systematic series of taps on the snow using his hand and shovel. The test isn’t complicated. “I start with ten taps from the wrist, if I don’t get anything then I get ten taps from the elbow, and if I still don’t get anything, I’ll get ten taps from the shoulder” Chabot explained. Those taps show how much force it would take to see if a slab of snow fails, and if the fracture propagates, which is one of the main ingredients you need for an avalanche to occur.

The video shows that the area we were testing was unstable, which has been common on many of the slopes in Montana this winter. It certainly doesn’t mean that people shouldn’t be out in avalanche terrain but does mean that you need to pay attention to the terrain. Doug explained that a pit doesn’t generally need to be more than 3 or 4 feet deep because the weight of a skier or snowmobile will not usually impact the snow deeper than that on any given slope.

If you do plan to go out, the GNFAC encourages people to check the avalanche report for your specific area at www.mtavalanche.com. You can also get more information about safety and online tutorials directly from their website.