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Friday, January 6, 2012



Avalanche!!!! The Snowpack Variable 


Snowpack is the last variable that we will use for clues.  By combining the clues you observe, identify and feel from the snowpack, a decision should easily be made whether or not the snow is unstable and has potential to slide. Some of the signs of avalanche are obvious.  The following clues are direct indications of instability in the snowpack: 


Recent Avalanche Activity 
Again, recent avalanche activity is the best indicator of dangerous slopes, especially when it is on slopes of similar aspect and steepness.  In other words, if you see the debris from a recent avalanche, know that there is danger of additional avalanches on similar slopes. 


                                              A bad day on the snow 
video

Recent Wind-Loading  
Recent wind-loading is another indicator of avalanche danger.  Smooth "pillows" and cornices as well as snow plumes of the ridge tops are indicators of wind-transported snow.  This means increased stress is being exerted on the snowpack due to the addition of the wind deposited snow.  Furthermore, wind deposited crystals develop dangerous "wind slabs," since this type of crystal is subject to numerous collisions while the snow is wind-blown. 


Hollow Sounds 
You must use your ears as you evaluate avalanche hazard.  "Drum-like" or "whumpf" sounds that occur under your feet indicate unstable slab conditions.  Also, pay attention to distinctive settling sounds; feeling the snow settle or drop are clues of an unstable layer of snow...indicating a dangerous avalanche condition. 


Shooting Cracks 
Look closely at the terrain you wish to cross.  Cracks in the snow around you are an excellent indicator of avalanche danger, especially if they are occurring around you as you move across the snowpack. You should not only avoid the slope where you see or produce cracks, but also any slopes with similar profile and/or orientation. 


Snow Stability Tests 
Through additional training, you can learn to recognize the weaknesses in the snowpack by evaluating a cut-away of the snow layers.  For now, just remember that avalanches occur when a weak layer in the snowpack fails.  Your ability to recognize these weaknesses will help you make an educated decision regarding safe backcountry travel. 


Conclusion 
In summary, by looking, listening and feeling you should be able to recognize, evaluate and avoid avalanche hazards that you may encounter on your next backcountry trip.  You must be thinking avalanche whenever you are on or near slopes, regardless of the slope size and time of year.  By always thinking avalanche you will be much more observant, you will gather more information from clues, and you will become a better decision-maker


For more information on avalanche safety check out the Mountain Rescue Associations public education program @ http://mra.org/images/stories/training/Avalanche.pdf as well as our Backcountry Skiing & Riding Safety Video  


Courage - Commitment - Compassion
     Mountain Rescue Association 

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