All Weather News

Avalanche! The Danger of an Unstable Snowpack

10 Feb 2017, 7:26 am

It’s something that still mesmerize us, young and old. The incredible power of nature. What starts out as a little bit of sliding snow rapidly grows and becomes one of the most destructive forces of winter.

Check out this video! Residents in Telluride, Colorado​ witnes…

Residents in Telluride, Colorado witnessed a controlled avalanche on Thursday. WeatherNationTV.com

Posted by WeatherNation on Thursday, January 26, 2017

Avalanche

Simply put, an avalanche is a rapid flow of snow sliding down a slope.
Avalanches typically grow as they tear down slopes entraining more snow and at times trees, rocks, and other debris.

They can be triggered by anything from gravity, to wind, to humans or animals, or even a change in temperature– just to name a few.
The one constant between each of these events is that avalanches are never random, and no matter the type there are always precursors to a slide.

Types of Slides

In each slide, initiation occurs when the load exceeds the strength of the snow.
The load is simply the weight of the snow, but the strength depends on everything from type of snow to the different layers of snow and even the steepness of the hill. And that just scratches the surface.

  1. Slab
    A slab avalanche is the most dangerous avalanche for backcountry skiers and snowboarders. Roughly 9/10 deaths in the backcountry are from slab slides.
    Slabs are the ones that look like a sheet of snow breaks off and slides down starting as one big piece. Hence the name slab.
    Simply put, a layer of the snow sheers off and slides down the slope. Giving those stark walls on the top and side of the slab.
  2. Wet Snow
    The slow slide. A mix of snow and water.
    Can often be incredibly destructive despite its slow speed because of the density and mass of the snow.
    Although these can be triggered by many different elements, they typically happen on warmer days where the temperature of the snow is near the melting point.
  3. Loose Snow
    These are the fast-moving, snow-spewing slides we all think of when we hear avalanche.
    Unlike wet snow avalanches, powder slides are typically a lighter snow with lower moisture content.
    Can be triggered by anything, but usually occur in fresh powder.
    Speeds can reach up to 190 mph! That’s faster than a skydiver plummeting toward the earth!

Triggers

The different types of triggers are endless. So we are just going to touch on a few of the more common types of initiation.

Triggered Controlled Avalanche

Washington State Department of Transportation triggers avalanche to control heavy snow on Monday. #WAwx

Posted by WeatherNation on Monday, February 6, 2017

For starters, you can stop worrying about the threat of an avalanche in your daily life. More than 90% of the avalanches involving people were caused by the person or persons involved. Basically, you don’t really face the threat of an avalanche unless you intentionally put yourself in that danger.

  • Natural
    These can be caused by anything that naturally occurs in the environment. (No human influence)
    These include things like rain, snow, wind, sun, earthquakes or a change in temperatures.
  • Human Triggered
    A human triggered slide occurs when the weight or action of a person adds a load the strength can’t support.
    The added weight can cause a snowpack that would otherwise be too stable to slide naturally to break free and potentially harm those involved.Contrary to popular belief, you actually cannot trigger an avalanche with your voice. No matter how loud you yodel!

Prevention

Prevention starts with education. By knowing the signs of avalanche danger you can avoid triggering a potentially devastating slide.

The National Weather Service puts out broad avalanche warnings when natural conditions favor an unstable snowpack. This can come from different types of snow and unstable layers within the pack to wind loading during a powerful winter storm.

Though these broad warnings are a great start, an even better way to go is simply checking with your local avalanche forecast center!
Check out the Crested Butte Avalanche Center Facebook page. This is a prime example of a small group of people going above and beyond to keep us all safe in the backcountry.

If you plan on spending significant time in the backcountry, there is no such thing as too much knowledge. A few things I can’t recommend enough are a beacon, shovel, and probe for your backpack– and a class that will not only teach you how to use them, but know the signs in the snow that might save your life.

For WeatherNation — Meteorologist Jeremy LaGoo

 

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