Avalanche Safety

Information from https://www.rei.com/learn/expert-advice/avalanche-basics.html. Please read that article for more in depth information.*

What is an avalanche? Avalanches can be big or small, wet or dry, but at their root, they’re masses of snow moving down a slope. Avalanches can be deadly, and an average of 27 people die in U.S. avalanches each year.

Main things to know:

Understand where and why avalanches occur: Learning this information will help you avoid avalanches when you recreate in snow-covered mountains.

Check the avalanche forecast: A network of avalanche centers in the U.S. provides daily forecasts with detailed information about conditions to help you prepare for your trip.

Carry rescue gear and know how to use it: It’s best to avoid avalanches in the first place, but if things do go wrong, always have the proper rescue gear and know how to use it.

Learn to recognize five red flags: Once outside, use your observational skills to recognize five key clues warning you about unstable snowpack.

Take a class: At the very least, take an avalanche awareness course. Consider getting more formal training. Get the education that matches your goals and comfort level.

Understand Where and Why Avalanches Occur

For an avalanche to occur, you need three things to happen:

1. Unstable snow

   Unstable snow is snow that wants to or can slide downhill. Weather, precipitation, temperature, wind, sun and many other factors influence snowpack stability.

2. Avalanche terrain

   Avalanche terrain is anywhere an avalanche can start, run or stop. Consider these factors when deciding whether you’re in avalanche terrain:

   *Steepness of the slope: *A slope has to be steep enough for snow to slide. Most avalanche activity typically starts on slopes between 30 and 45 degrees. Some slides can happen on lower angles but they’re not common. It can be hard to estimate slope angle; a slope meter (inclinometer) is a useful tool to measure slope angle quickly.

   Connected slopes: Avalanche terrain is anywhere an avalanche can start, run and stop. If you’re traveling in more gentle terrain but it’s connected to steeper slopes above you that can slide, there’s still a risk of an avalanche.

   Terrain traps: These are features like gullies, rocks, cliffs, trees or crevasses that can magnify the consequences of an avalanche. If you get caught in an avalanche, terrain traps will make even a small slide worse because they increase the risk of injuries or make it more challenging to dig someone out. A small slide can cause traumatic injuries if it barrels you into hard objects such as trees or rocks, sends you off a cliff, or buries you deeply in a gully or depression. Most people who die in avalanches do so from asphyxia (typically because they’re unable to breathe when buried) or trauma.*

3. A trigger—natural forces (such as wind) or human-induced (such as a person’s weight traveling over weak snow)

   Natural triggers such as snow, wind or rain can cause avalanches. But most avalanche accidents are triggered by the subsequent victim or someone in the victim’s group. A skier, snowboarder, snowshoer, snowmobiler, climber and others can all trigger avalanches (such as by moving their weight over unstable snow). So the decisions you make about when and where to go and how to travel can make a huge difference in preventing accidents.

Check the Avalanche Forecast

Forecasters in the U.S. and Canada use a universal five-level warning system called the Avalanche Danger Scale; it lets recreationists know about the potential avalanche danger over a specific time period in certain mountain regions. A network of regional backcountry avalanche centers in the U.S. provides daily avalanche forecasts for many mountainous regions to help people understand where avalanches may occur. Check the forecast daily because conditions constantly change.

Carry Avalanche Safety Gear and Know How to Use It

Since most avalanches are triggered by a person who ends up trapped or someone in the group, it’s crucial that all members of your group carry essential avalanche rescue gear and know how to use it. At a minimum, each member of your group should have an avalanche transceiver, a probe and a shovel.

Recognize Five Red Flags

Here are five red flags of unstable snow:

1. Recent avalanches: If you see signs of recent avalanches or forecasters tell you there have been recent slides, it’s a clear warning to avoid avalanche terrain. If you can’t tell whether an avalanche was recent, assume that it was. One clear sign of a recent avalanche: if you see piles of chunky snow (avalanche debris). Or if you look up at the mountains, you’ll see the vertical face (called the crown or fracture line) where the avalanche has pulled away from the snowpack.

2. Shooting cracks: When unstable snowpack collapses under a trigger, cracks may shoot across the snow surface and can sometimes run for tens or hundreds of feet.

3. “Whumpfing”: This is the loud noise you may hear when unstable snowpack collapses under you or your group. As the air rushes out of the snowpack, it goes “whumpf.” (Yes, that’s the technical term adopted by avalanche forecasters and educators). Where shooting cracks are the visual clues, whumpfing is the audible one. The two can happen at the same time.

4. Big changes in weather: If you’re experiencing big changes in weather, you should expect big problems. Recent rain or heavy snowfall means the conditions are there for unstable snow. Strong winds: Look for surface patterns on the snow made by strong winds, which could indicate that snow has been transported and deposited in dangerous drifts that can release and run. Pay attention to cornices and drifts on steep slopes. Rapid temperature change: Beware if you experience rapid melting, which can affect snowpack stability.

5. *Persistent slab avalanche: *This is a type of avalanche that forms when a weak layer of snow is buried by other layers of snow. While most avalanches occur during or after a storm, persistent slabs can occur long after a storm has ended and are disproportionately responsible for avalanche fatalities.

Take an Avalanche Safety Class