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So I just learned that there was a pretty large 1.5 slab avalanche on the Hiyodori slide path above Tsugaike on Monday, February 11th (yesterday).

 

The slide crossed the higher cat track and went as far as the second one.

 

Does anyone have any more info on this - was it skier triggered? Was anyone hurt or injured?

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  • SnowJapan Admin

Feel free to talk about it if you like and if really what you want to do is share the information.

 

Don't feel free to simply post links to your blogs or tell people to google the name of a website.

It's annoying, especially when it happens time after time, same people same people.

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So we cant share we saw information that is relevant to a discussion if its outside of SJF, David? I purposely didnt post a link nor did I mention a blog nor am I in anyway associated with the source of that info? Not sure how what I did is outside the rules????

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:( Yesterday morning we saw the heli flying, apparently out to the site. They were bombing and testing cornices and wind lips on the Cortina side yesterday prior to opening.

 

From the Cortina FB page just now:

 

TERRAIN REPORT  

Lift Operations:

No. 1 lift (8:30~17:00) OPEN

No. 2 lift (8:30~17:00) OPEN

No. 3 lift (9:00~16:00) OPEN

No. 4 lift CLOSE *all day * Due to high avalanche hazards.

No. 5 lift CLOSE *all day * Due to high avalanche hazards.

No. 6 lift (8:30~16:30) OPEN

No. 7 lift CLOSE *all day ※Open on weekends

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whilst on my travails, i was fortunate enough to find myself on a seriously shitty (southwest) face in the trees. Didnt do a pit test, but was slightly alarmed by the size of the chunks breaking away so figured id spend a couple of minutes to try and figure out what i was seeing.

 

There is (or rather WAS since the snow is dropping) a slab layer of about 10-15cm (sorry, didnt measure it, was busy contemplating the crap i was in...but based on my mental visualisation right now), siting on top of a weaker layer of about 3-5cms which it hadnt quite bonded to of looser snow (im sure with the new snow though, itll bond pretty well). And under THAT was a grainy layer which is the weak layer that people are talking about.

 

Sorry, im not very scientific so the info is messy, but somewhere around the 20cm mark is/was a layer thats probably going to rip on first contact. While i was riding it, it was mainly breaking off below you, but that the top layer is seriously bonded, and the new snow will add extra weight which will compress the looser making it effectively: weak layer, slab, todays snowfall. Which puts the slab directly on top of the weak layer and on top of that is the extra weight from the fresh snow.

 

So with the new snowfall compressing the weight and causing the snow below that slab to pack in, you get a direct link to the weak layer hiding under the slab hiding under the fresh snow. So pressure on that weak layer will likely fracture a much bigger area and maybe the whole slab ABOVE you. What im trying to say is that this crispy/slush-ice layer about twenty cms down is rolling super easy and the snow above it is going to be so well bonded that when that layer slides, chances are youre on a rolling log downhill :)

 

I think thats it? :confused:

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Its quite common to see new fresh snow (soft slab) sections release on a harder layer beneath (sun, rain or wind crust).

Is this what you were seeing or larger sections of older harder snow releasing? Soft slabs are to be expected with new snow but hard slab activity is a big worry.

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ive actually got a picture of it on my gopro. Alas its at home.

 

The slabs were really compressed though. Ive only seen it once to be honest (more lack of actual experience than it being super rare), so it gave me cause for worry. What im thinking is that the situation on sunday was the former one, small breakaway and broken up parts of the slab about 10x30x20cms coming from under you and sliding down, but i think that was actually teh softer looser layer basically causing the weight to simply snap it off below where the board/weight impacts on it (if thats making sense?). And when you did dig down to the weak layer (it was terse and grainy, kinda like frozen slush - but not completely unbonded, just really easy to break up though), the loose snow directly above it meant the damage you could do was pretty localised to the immediate vicinity of where youre directly riding.

 

Sooooo... when i rode it chunks were breaking off under you, but above you wasnt really impacted. I think that softer layer underneath almost acted like a buffer or a cushion against that weak layer. Its when you hit the weak layer it sloughs on you and you get that rolling feel. What im thinking is that the loose layer bridging the fresh slab on the top and the weak slush/ice layer isnt LOOSE-loose, but actually in the process of bonding to that top slab and needed a bit more time/compression.

 

And then this weeks snow is going to add weight to it, and bury it. Because that weak layer breaks off almost on immediate contact with it, and that slab will likely be sitting directly on top of it, when you put some weight on it its pretty much going to go and go pretty big. As i say, its just trying to work out what i was looking at. Hopefully its making some kind of sense :)

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Sounds like wind slab sitting on a melt/freeze layer. You will be surprised how fast it does bond to the melt freeze layer here in japan. I dug a pit last week and found the feb 2 melt/freeze layer that I knew was there and also another one about 40cm beneath it and the other snow had bonded really well to it,which I wasnt expecting .This layer actually strengthens the snowpack now as it has become a stabilizing layer.

You should go back out there next time you get a chance and dig to see what has happened. Getting to know the snowpack can be fun, I quite enjoy it.

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The knowledge you people have... how you could work out that from what i wrote is genuinely... wow! :)

 

Kk, ill go do a pit test next week for a giggle. Itll also give me a reason to get that last break even day at nozzie! (the season pass is about to pay for itself at last!)

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Horrible news. Thoughts to his Family. I've been hitting back country for the first time ever this season. I never go out with out a Beacon, Shovel Probe and crew of people who have the same and know how to use them. I guess its just so easy to be complement when you dont know what you are really dealing with. Particularly dangerous when the snowpack is pretty dodgy this time round.

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He was wearing a beacon but was alone

 

Well, perfect example of how useless the gear is with out the right people around you. Would of been better off in a high vis vest. Did they find him in the end? Last I heard they hadnt.

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We all know that but not everyone has a crew ready to ride at all times. I ride alone a lot and its the risk you take. I just try to ride familiar terrain as new terrain can catch you out easily.

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An avalanche airbag may or may not have helped, also. If you ride solo a lot it's definitely something worth thinking about.

 

Of course if you ride solo there are a million other hazards that are more likely to get you before an avvy.. Things that wouldn't be a huge issue with a group but potentially life threatening if you're caught out alone

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Heres that pic, just so you can confirm your hypothesis: Basically cleared out the loose unbonded stuff under it, and under that is a thin layer bonded to the melt/freeze . On the day it rolled really easy if you dug through to it. Like almost instant rip away causing (small) slough slides. It pulled me away with it on one occasion but the board dug in again and i could arrest the slip. So maybe under that is a nicer layer or something, i dunno :) Fun learning about it though and trying to figure it out.

 

gallery_10042_188_1511996.jpg

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