Should you test the snowpack for instability?
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- čas přidán 11. 12. 2020
- Bruce Jamieson and Doug Chabot talk about why, when, where and how to test for instability in the snowpack. The Extended Column Test is demonstrated along with a discussion on site selection and interpretation of results.
Best avalanche video Ive watched on YT
Clarity has actually been quite a common problem in the avalanche education community for some time. Snow pack indices was also fraught with these kind of issues of false negatives. Adding up the number of layers and interfaces to show instability when it exists is a good idea, but not when it doesn’t exist, and vice a versa.
Jamison understands statistics in regards to probability and does an excellent job at staying away from complicated explanations of test results. They scratch the surface about sensitivity and specificity. Forecasters and educators need to understand positive and negative predictive values as well as number needed to treat and harm, and type 1 & 2 errors. It’s the only way we can truly pass this information along to somebody else and help BC travelers to make those decisions when presented with information from their snow tests. Otherwise, if students cannot interpret tests on their own, there’s no reason for them to do them.
Really nice video!
One of the best stability videos that I have seen
A+ video - so many times I hear that a stability test is a "safety step". While it clearly is, awesome explanation as to why a test should be telling you NOT to ski/ride something rather than give the green light. Thanks for taking the time to make this.
WOW, now this is what I call a VIDEO, ALL the right words spoken (used) and anyone can learn from this video. EXCELLENT VIDEO, PERFECT! / I've always made 3 snowpits, atleast 10-15 feet apart from each other. Each pit I make is a minimum of 5 feet deep and 5 feet wide.
I always emphasize to my students that one should never make a "go" decision on a single test but one could certainly make a "no go" decision if things look questionable. (I.E., an ECTP at any number.) I like the concept of "we're hunting for instability" and the term "instability" tests. I also really like the quote "You can't outsmart instability!" (Like if the avy report says Considerable at a certain aspect and elevation, just avoid that terrain.) Great video! P.S. I like to pull the probes out before sawing so I'm not damaging them.
Love all your videos! Super educational as always!
Helpful video, great work 👍🏼
Thank you for this video and the very well done instability testing explanation.
Excellent video. Really helped me as a refresher for knowledge and skills. Thank you! Great channel, too!
Awesome knowledge - thank you!
Excellent Video! very concise, you have redirected my thinking for the ECT
Thank you, great content!
Thanks for this super informative video!
Thank you this helped so much ! Key points simplified
Given who the presenters are, I am not surprised by the excellent information. What was a pleasant surprise is how well it is explained and presented it was. Highly recommended, even to beginner users like me.
One point to expand on might be how an ECTN result indicates that a slab isn't present where (and when) you dug your pit. Not that there aren't slabs elsewhere (or not yet). A weak layer exists, but no slab. If warming occurs throughout the day, snow could become more cohesive and form a slab. Or if the wind picks up.
very educational. thanks for helping people stay safe
Great information. 👍🏻
Thanks, excellent descriptions, dialogue, explanations etc. Especially reminders on " this is a instability test, not stability test" would appreciate more discussion of spring 1" comment. Have some experience here and would appreciate your thoughts. Thanks!! Really appreciate!
When the upper snowpack has melted and refrozen many times, the skiing is best when the riding is best when the snow surface (aka corn snow) has "started to soften" or something like that. I proposed "less than an inch" to emphasize that the soft - sometimes wet - snow on the surface should be limited and not enough to start a wet loose snow avalanche.
Such a great channel. Does a chart exist showing different test results correlated to avalanche potential?
He said at 12:45 "we're saying ECTN's in the 20s" to describe Low probability. Is there a chart laying those out?
See Table 6 here nhess.copernicus.org/articles/20/1941/2020/
Oops, see Figure 6
@@brucejamieson perfect!
Newbie question. Avalanches trigger at weak layers and propagate to create the slab. Sah you you did an ECT to test a PWL generally found at 55cm and had the result ECTX. Then you dig a pit to do an ECT but find the snow is shallower there so the PWL is around 40cm and had the same result, ECTX. My understanding is that you still don’t take that as a sign of the slope being ok to ski because you could find a different weak point to trigger (e.g. maybe around a rock or tree branch). Is that correct?
The bit at 13:00 isn't really helpful. "Dig your pit, make your observations, then discard the observations and think about what MAY happen IF any number of VARIABLES were different than in this specific pit." No kidding... There is always somewhere on the mountain that will offer worse outcomes. If you're just going to always assume that you're going to cross terrain somewhere that will slide, don't ever get on or under something over 30 degrees and skip digging pits.
You ALWAYS CHECK the snowpack for Instability, 100% of the time, period.
I had a friend that wanted to go backcountry snowboarding with me. I asked him about his avy training and had none, but still wanted to go. I then said he may very well end up entombed and there would be little to nothing I could do without proper beacon equipment on his part. He laughed at the word "entombed" until I explained to him how snow turns fluid during the avalanche then freezes up like cement when it stops and whatever position he ends up in (including upside down) will be his frozen tomb where someone may eventually find his body (not person) in the last position he was in before the avalanche suddenly stopped.. He stopped laughing and never asked me again.