Avalanche Awareness: Backcountry rangers keep a close eye on snow conditions to keep you safe in the mountains

Dan Frigaurd, a ranger with the Coeur d’Alene River Ranger District, is going to create an avalanche.

After he announces that “it’s snowshoe time,” Frigaurd straps on a large pair of snowshoes and begins hiking, alongside a pit dug on a slope in the Lookout Pass area.

When he gets directly above the isolated slope, Frigaurd cautiously positions himself on it – after getting in the middle of the slope he begins applying pressure. Slowly he adds more and more pressure. Nothing. Then he begins making small jumps. Still nothing. Finally, a higher jump produces movement. Frigaurd slides down the slope, snow falling underneath him.

This final “long, big test,” as Frigaurd calls it, is just the first in a series that he and Carole Johnson of the Superior Ranger District conduct on their weekly avalanche stability tests in the Lookout Pass area. Their findings and test results are sent to offices in Missoula and the Idaho Panhandle.

“Tomorrow morning this information will be compiled with other people who are out doing the same thing that we are doing today in various locations,” Johnson said. “This information will help make up the avalanche advisories that will be posted on the website tomorrow morning.”

Every week Frigaurd and Johnson meet at Lookout Pass Ski Resort and then take snowmobiles to different sites in order to conduct their stability tests.

“We try to find a slope that is representative of a slope that people would be recreating on but is in a safe spot for us to do our stability tests,” Johnson said.

The rangers are careful to vary test locations, making sure to choose both northern and southern facing aspects. This accounts for temperature, wind and other differences depending on the location.

On Feb. 9, Frigaurd and Johnson took their snowmobiles to a site just south of the ski slopes and quickly found a suitable southwest-facing site to serve as the first test area. Ideally, the rangers choose a slope of snowpack that has between 30 and 35 degrees of steepness, the first site had a slope of 33 degrees.

“That is a slope that is obviously typical avalanche terrain,” Johnson said.

Frigaurd then begins digging a pit at the base of the slope in order to take a profile of the snowpack, similar to a soil profile. This will show how the snow has compressed as more and more snow piled on.

“We try to get something that nobody has been on so that our tests are as clean and reliable as we can get,” Frigaurd said while digging the pit. “It’s looking good ,you can already start seeing layers in the snow from either sun crust or some sort of freeze-melt.”

After the pit is dug, Johnson and Frigaurd take various measurements, such as snow and air temperature, determining what location the aspect is in using a GPS device, wind and other factors.

“You obviously can start seeing some layers right off,” Johnson said. “What we are going to be doing is performing a variety of different stability tests to see how much force is required to make the snow fail in those different layers.”

Frigaurd’s pit uncovered five distinct layers of snow at a total depth of 64.5 inches, with five inches of new snow. To determine what type of snow is in the various layers, Frigaurd conducts a fist test on the different layers.

First he tries to push his fist into the layer, if that doesn’t work he goes to four fingers, then a finger and finally a pencil. A fist represents snow that is least dense, while the pencil represents snow with the greatest density.

“You want your snow profile to be dense on the bottom with less dense snow on the top,” Johnson said. “The pyramid is correct for the snow pack we tested”

Frigaurd then grabs his snow shovel to begin a series of stability tests. The rangers conduct multiple tests to determine if they all show the same weak layers in the slope.

“These are tests that really anyone can do in the field,” Johnson said. “Anybody that is out recreating or traveling in avalanche terrain should have a shovel with them.”

The first test is called a shovel sheer, where Frigaurd uses a saw to isolate a column of snow and then applies a prying force with the shovel to measure how much it takes for layers to fail. This test also showed that the snow is packed ideally.

“Since we are sending this information to the avalanche advisories we take quite a bit of care to really get accurate results and are confident in the information we give out,” Johnson said.

Two compression tests are also performed. One with a shovel width column of snow and the other with a column three shovels in width.

After columns are isolated, Frigaurd places his shovel on top and begins tapping on it before hitting it with more force. In both tests, it took what Frigaurd called “a lot of whacking” in order for the columns to break at the lower ice layer.

According to Johnson, these two tests are extremely reliable and provide valuable information to the avalanche advisories. Frigaurd and Johnson make sure to do the same tests in the same manner every week, often in the same locations to ensure that they are consistent in monitoring how the snow pack changes from week to week.

“Anybody that’s going to be travelling in avalanche terrain needs to know what the snow pack really is,” Johnson said. “Very few people will take the time to dig the pits and do the extensive testing that we’re doing.”

Johnson added that since information from the avalanche reports are only from areas where rangers test, they encourage recreationists to perform tests in the areas they will be using for outdoor activity.

“We are always available if any individuals or groups of people are interested in avalanche education,” Johnson said. “We do indoor sessions and also field days to educate the public on avalanche safety.”