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Avalanche Danger Scale Definitions Review

post #1 of 4
Thread Starter 
With all the avalanche action happening here in Colorado the news media (TV, radio and print) have been talking about the avalanche danger. But, when they start talking about the avalanche danger, they consistly screw-up on the definition of each danger level.

So, let's have a little review here. I know that I cover this in my courses a lot.

People seem to have a real problem understanding the difference between the Moderate and Considerable dangers levels. As it turns out more folks are killed during Considerable danger then during High. I think that a lot of this is because people don't understand the "Considerable" danger level.

Avalanche forcasters decided on what danger level to post, based on if natural avalanches are happening or the likelyhood of human triggered avalanches happening. So, keep that in mind.

Avalanche Danger -- Natural triggered -- Human triggered

LOW --- Unlikely --- Unlikely

Moderate --- Possible --- Possible

Considerable --- Possible --- Probable

High --- Likely --- Likely

Extreme --- Certain --- Certain

To me, the word "Probable," means that there is a VERY good chance of something happening. The dictionary defines Probable as "likely to be or become true or real."

I hope this helps folks. Reading the daily avalanche center forecast is the best way to keep up on the weather and snowpack trends. By becoming a "Friend," of your local avalanche center you can have the daily forecasts emailled to you. And it will give you a nice warm fuzzy feeling, that you are supporting you're tipically underfunded avalanche center.

For the Colorado Avalanche Information Center


Halsted Morris
post #2 of 4
I don't remember who said it, but

"I wouldn't walk into a bar I had a moderate chance of dying in" or something like that.

Since Hacksaw posted ColoRADo,
here's Tahoe


I agree that probable human triggered should be a red flag. I think considerable being in the 'middle' of the scale causes some heuristic traps for people.

Ultimately, the forecast is only a forecast. Think of your weather forecast, how often is it right on the money? It is one tool to determine stability. You need to know how to determine stability on your own and then use your observations in conjunction with the avy forecast to decide if a slope is going to go or not. And then, obviously, have the tools and the training to use those tools when something goes wrong.

I'm just glad ColoRADo newscasts mention the avy forecast. Reno newscasts seem to dissuade people at all from heading into the backcountry. "If you go into the backcountry, you will die" sort of slant. Of course, I kinda like that. It keeps the gapers out.
post #3 of 4
Probability of being hit by high speed skier or snowboarder:

Trail NOT Groomed = LOW --- Unlikely --- Unlikely

Deep fresh untracked powder = LOW --- Unlikely --- Unlikely

Trail Groomed = Moderate --- Possible --- Possible

Ski deep untracked powder. Its safer :
post #4 of 4
Monday morning on the Boulder NPR station, they indicated that the "Considerable" label is particularly dangerous, as the danger is much less obvious than with the High or Extreme conditions. Makes sense. People are more likely to be killed when there are conditions favourable to a slide, but it is less obvious that a slope might slide. This suggests that the danger scale might be different than the scale that measures the probability of a slide.

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