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| | |-+  Mt Hood observations Saturday Feb 22
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Author Topic: Mt Hood observations Saturday Feb 22  (Read 4407 times)
james bleuer
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Posts: 4


Mt Hood observations Saturday Feb 22
« on: 02/24/14, 05:37 AM »

above Tilly Jane, near treeline on Saturday we dug some quick pits and was wondering if anyone else would contribute their results or interpretation.  I'm VERY new to this and don't get up as much as I wish I could, so please forgive my ignorance and thanks in advance for helping me build my knowledge base here

Apologies for lack of pictures... One interesting pit we dug was around 6300ft, just below treeline but in a bit of a clearing, N aspect, we dug below the rollover to a 25degree open slope.  NWAC had a general considerable rating for this area as far as I remember.  The results we got varied quite a bit

- while isolating the first column we had a failure around 20cm, Q1, but could not replicate this
- shovel shear tests clearly showed there were 3 layers we could produce a clean shear in the top 1m
- we really wailed on it during an extended column test and no failure
- a half effort rutschblock test where we made about a 1.5m x 1.5m block and I lightly stepped on it with no skis gave us clean failure 20cm down

My thoughts are that it was a very variable spot to dig a put, even as we were there the wind/snow changed direction several times - but I wonder how others would interpret it or what they actually saw on Hood this weekend.  Clearly I need to read up on my materials this week, and I will. 
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garyabrill
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Posts: 522


Re: Mt Hood observations Saturday Feb 22
« Reply #1 on: 02/24/14, 09:52 AM »

It is impossible to interpret what you saw in your pit without being there. It is safe to say that new snow layers are usually a little hard to interpret. Digging in the snow is always educational but in situations like this is not always the best to base decisions on. I would put more credence on the the avalanche forecast and for a particular slope, it's shape and the likely interaction of the wind with said slope. Considerable says that human triggered avalanches are probable, it just doesn't say where.

I'll dig in new snow layers with my hand often, with my shovel when I'm curious. But I would generally dig when there is a known weak layer within the range of depth where triggering is likely. For more deeply buried weak layers, if I dug and tested it would be out of curiosity as I would likely have no way of knowing whether I might affect such a weak layer except by slope shape.

It's important to realize that digging or testing is a search for weakness and not necessarily effective for basing decisions on.
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Koda
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Posts: 248


Re: Mt Hood observations Saturday Feb 22
« Reply #2 on: 02/24/14, 01:38 PM »

clyde, the location of your test needs to be representative of the slope your going to ski, nothing to do with the wind. Snow pit tests need to be clean and precise, not half effort, ...with practice can be done very efficiently. My advice would be to learn one test at a time IMO start with the ECT test and understand how propagation works. Snow pit tests are not an indicator of stability, there are no “green lights” in avalanche terrain and any evaluations in the field are only an understanding of the risk involved especially pit tests. 
What were the indications of instability in the slope you skied?
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