A question we often get asked is "How do you forecast?". Here are a selection of views and differing methods to help you piece together the Avalanche Triangle, which always contains you--the human--as its centrepiece.
Avalanche Forecasting - A Modern Synthesis by Ed La Chapelle, 1965.
Snow Avalanches: Their Characteristics, Forecasting and Control by Edward R. LaChapelle,1962.
Avalanche Hazard Evaluation Field Checklist by Doug Fesler and Jill Fredston.
How I Forecast for the Back Country by Rod Newcomb.
Safe Skiing - Stop Light Metaphor by Brad Meiklejohn.
Rules Of Thumb by Ron Perla.
Open Book Questions - to encourage reading the ABC's of Avalanche Safety, by Ed LaChapelle.
And view our links page for further online resources!
Snow avalanches are a natural process, occurring perhaps 1,000,000 times per year, world-wide. They are one way for snow on an incline to adjust to the pull of gravity. The vast majority of these slides are not a problem, because an avalanche, in and of itself, is not a hazard. A person (or a person's belongings) has to get involved in order for there to be a problem.
The fact is, that avalanches don't drop from the peaks onto the heads of unsuspecting innocents with the unpredictability of a plummeting meteorite. 95% of people who are caught in avalanches are caught by a slide that was triggered by themself or a member of their party.
I think this is good news! Our behaviour creates the hazard, so we can change our behaviour to avoid problems.
There are many different types of avalanches, but the one that worries us the most is the "slab" avalanche, in which a mass of cohesive snow releases as a unit. This type is easily recognized by its distinct crown and flanks (click for a diagram of the nomenclature associated with avalanches).
Slab and other avalanches can be hard or soft, wet or dry and can be triggered naturally or artificially.
Spotting Avalanche Hazard: The Avalanche Triangle
Some places have avalanches: Switzerland's Alps, Utah's La Sals, Nepal's Himalayas, New Zealand’s Mountains. Some places don't: South Viet Nam, the Mile-High Stadium, your living room (the distinctions are not always so obvious, unfortunately).
Why is this? Avalanches are formed by a combination of three things that together are known as the "Avalanche Triangle". These 3 ingredients may be present in one location but absent 10 feet away. The three legs of the triangle are Snowpack, Terrain and Weather.
There are many tip-offs to the presence of a potential avalanche, including surface clues and active stability tests. You should never trust a single information source--stability evaluation is an ongoing process!
The information from this page originates from www.avalanche.org.
The Mountain Safety Council is an important advocate of outdoor safety in new Zealand. They have an excellent brochure on avalanches, how to recoginise danger and how to prevent them. Their website has further resources available that you might want to explore. It also contains saftey tips for in summer time.
MSC also runs a website with backcountry avalanche advisory which is provided as a public service. It is intended as an advisory only.
Avalanche forecasting is an undertaking which requires extensive study and field observations. Those endeavouring to travel in the Southern Alps and the mountains of the North Island, do so at their own risk. We recommend winter travellers be well informed about current weather, snowpack and avalanche hazards.
Winter travellers should not travel alone. All members of your party should wear a transceiver (457khz) and know how to use it. In addition everyone should carry a shovel, and a probe. Winter travellers should advise someone where they are travelling, and when they will make next contact.
The Department of Conservation can assist with safety advise. Check their website for more details.
Before teachers take classes on snow trips they should have all students fill out a risk assessment forms. This is called risk management.
The forms help to identify all of the possible risks that may occur during the trip. The next step is then to work through scenarios how the grooup will respond in case one of the scenarios happens. Each of the scenario's should be worked through to make sure they have the right equipment, first aid, support systems, and procedures in place before they go.
They are then prepared for every possibility.
The Avalanche Lady covers risk management in her speech and can help school groups with providing the risk assessment forms.