Trent Ernst, Editor
Last Week, Avalanche Canada issued a Special Public Avalanche Warning for recreational backcountry users across most of the province. The warning was for most of the province, but not the Northern Rockies.
After the warning went out, the Peace Region got hammered with up to 20 cm of fresh snow.
The new snow on a well settled base means far more active avalanche conditions in a region that has seen little avalanche activity this year.
On Saturday, a rider was killed by an avalanche in the Torpy Mountain range, about 100 km southwest of Tumbler Ridge. While not part of the Tumbler Ridge riding area, it is part of the Northern Rockies area.
The rider was one of a group of five who were out in the area.
Search and Rescue executive Sarah Waters says that, while the Avalanche warning was not for the Northern Rockies, the storms that caused the warnings have caused similar conditions in the Peace.
Snow storms across the province have buried a weak layer that is particularly prevalent at lower elevations. However, due to the amount of new snow, all elevation bands are potentially hazardous, says James Floyer, Avalanche Canada’s Forecasting Program Supervisor.
“We’ve had a relatively stable snowpack up to this point but things have changed now,” says Floyer. “We urge all recreational backcountry users to recognize this shift and to exercise more caution. Staying safe in the backcountry this weekend requires selecting simple, low-angled terrain, even when you’re at lower elevations below treeline.”
The most recent updates to the Mountain Information Network from the Core Lodge says that the top 15 cm of snow is highly reactive. On January 23, rider mckayryan7 reported “15 to 20 cm of fresh snow fell in Core Lodge the other day. The snowpack depth varies depending on the aspect. During compression we found the top 15cm to be highly reactive. We also had moderate results down 37 cm where the facets meet the setup snow. There was some point release avalanches observed on terminator face.”
Farther north, Trapper Gilowski reported slab avalanches in the Bullmoose area, and reported “whumpfing or drum-like sounds or shooting cracks and 30cm+ of new snow in the last 48 hours.”
“Today in the Bullmoose riding area we noticed signs of snow instability from shooting cracks to tiny slabs setting loose on convex features in the ditches,” says Gilowski. “In our pits we had compression test results in the easy range down 15-25cm siting on surface hoar and faceted grains. Lower down 40-50cm in the moderate range we had another layer reacting on facets. Conditions have changed with the new snow fall. Remember to play safe out there.”
If you have been traveling in the mountains, Avalanche Canada would appreciate your observations. Please send them to: firstname.lastname@example.org, or upload observations to their new Mountain Information Network on their website, or via their app.
They warn that all backcountry users must be equipped with essential avalanche safety equipment. Everyone in the party needs an avalanche transceiver, a probe and a shovel. It’s equally important everyone has avalanche training and has practiced using this equipment. If an avalanche occurs, the rescue is up to you. There is no time to go for help.
The quality of snow that lands on the ground is affected by temperature, humidity, wind and the amount of snow that lands, which varies from snowfall to snowfall.
In addition that snow is then affected by a variety of other factors: sun, wind, humidity, temperature, rain, etc. acting on the surface of the snow, which changes the snow from its original form.
As fresh snow falls on top of the previous snowfall, it creates another layer, which has its own qualities. And, as moist air comes in contact with the surface of the snow, it can cause a layer of frost to form over top the previous layer of snow.
How well or how poorly these layers hold together is one of the major factors in determining the avalanche conditions of an area.
Note that many of these factors (sun, wind, etc) are localized phenomenon in the mountains. The sun can hit one side, or even one area of a mountain, but be blocked by a peak across the valley, creating two different avalanche conditions on the same slope.
Just to make things even more complex, the sub-surface layers can change over time, due to internal snowpack conditions (such as temperature, pressure, etc.). This will also change the avalanche danger to be found in an area. Factors that drive change in the layers of the snowpack are always present; therefore the layers are constantly changing. This change can be rapid (e.g. freeze-thaw of the surface layers) or slow (e.g. long-term metamorphism of the sub-surface layers).
The other main factor affecting whether an avalanche will form or not is the terrain. The main feature of avalanche terrain is the angle of slope. Typically, avalanches happen with a slope angle of between 25 and 45 degrees. Greater than 45 degrees, and the snow has a hard time sticking. Generally, the snow will just sluff off, not allowing larger avalanches to form.
Below 25 degrees, on the other hand, the angle is not steep enough (generally) to cause the snow to slide.
Trees and large rocks can act as anchors, though if the snow is deep enough to cover these features, then all bets are off. And sparse trees can actually create weak points in the snowpack, causing things to trigger easier.
Avalanches are more frequent at higher elevations, which are often steeper and get more snow and wind than lower terrain. Also, there tends to be fewer anchors higher up.
There are eight different types of avalanches that commonly happen in the mountains around Tumbler Ridge.
The first is a loose, dry avalanche. These often happen when the soft powdery snow that has just fallen looses cohesion with the bottom layer and start to slide. These are generally smaller avalanches that happen on slopes greater than 35 degrees.
Loose, wet avalanches, like dry avalanches, typically only affect the surface layers, and are generally very small. However, as the snow is wet, they are denser than dry avalanches, making them harder to fight against if someone gets trapped in the avalanche. Warning signs include small, snowball sized chunks of snow rolling down the mountain.
When a thick, cohesive slab of wet snow loses bonding with the layer below it, you have a wet slab avalanche. These can form on slopes that appear firm and not prone to avalanches, and happen when the layer below is weak. Because they are wet, they tend to move slower than dry slab avalanches, but they can be highly destructive because of how heavy the snow is. These avalanches tend to form into channels, and if you see one, there’s a good chance that other terrain in the surrounding area is setting up to go. They tend to occur in the late spring, after the snow has had a chance to warm up.
The fourth type of avalanche is a storm snow avalanche, and occurs during or after a large storm as the new snow load gets too heavy to stick to the layer below. These are the most commonly known avalanche type in this area, but only last about two days after the storm. And therein lies the danger, as many people assume that if they wait 48 hours after a dump of snow, they’ll be safe. As you should be figuring out from this list, that is not the case.
Wind slab avalanches are caused, you guessed it, by the wind. These are caused by wind packing a layer of dense snow over top a weak layer. These layers are often called pillows, and often sound hollow when crossed. They tend to develop during blizzards or other windy periods. They tend to stabilize after a few days, but can last longer if it is cold.
Persistent slab avalanches and persistent deep slab avalanches are among the most dangerous and destructive avalanches. And form when snow builds up on a weaker layer. In the earlier stages, persistent slab avalanches are usually small and easily triggered, but as the top layer becomes more cohesive, and as the lower layer does not bond, the amount of snow that can be triggered by a deep persistent slab avalanche is staggering, and quite often fatal. Even worse, they can become dormant for extended periods of time, then re-awaken with horrific results. Often this re-awakening is brought on by spring, when they can go without warning.
Finally, skiers and sledders need to watch out for cornice falls. A cornice is a mass of snow that is deposited by the wind on the edge of a ridge. As the wind blows over the ridge, the snow swirls back and attaches to the edge of the ridge, creating a ledge that extends out beyond the ground. They are not supported from below, and, if a sledder or skier moves out onto the cornice, it can give way, with often fatal results. Even worse, they can often trigger other forms of avalanches when they hit the slope below.
Different types of avalanches behave differently, but there are a couple clear signs that you might not want to be out on the snow right now. If you can hear a whumpfing sound and see the snow start cracking,