Inbounds slide report: Heavenly, NV

I managed to kick off another inbounds slide on Friday. (For my previous efforts, see this thread and this thread.)

This happened Friday at Heavenly in Killebrew Canyon. Snowphone reported 9" new, but 60MPH SW winds (gusts to 100MPH) the night before meant actual depth ranged from about 3" of windboard to over 2' of wind deposit.

Unsurprisingly, given the wind direction and magnitude, NE-facing chutes held the deepest and best snow. E facing aspects were slightly denser from windpack but still excellent. NW and W aspects were pretty hammered, particularly at the top of the mountain, which was scalloped into beautiful but hard, and mostly unskiable, forms.

I was able to see the aspect I later skied from the S ridge of Mott, after patrol bombed it but before it opened. I noted several small sloughs in the usual places (Pipeline, Ramarrah's), but no major slide activity, which is unusual...those chutes are steep enough to slide consistently from control work.

Most of the new snowpack was homogenous, but local contours appeared to cause several small localized windslabs. In retrospect I believe them to be from areas with low skier traffic, probably partially or completely untracked from the day before: areas with higher traffic had enough tracks to keep the snow anchored. Anyway, I broke off a tiny windslab in a low-traffic N-facing rollover in Mott Canyon from a ski cut: perhaps 10' x 10' x 6" deep, which should have prepared me for what happened later in the day.

Fast-forward to the run: I dropped into the rock garden between Pipeline and Ramarrah's. Aspect is NE. It's pretty tricky in there, with lots of trees and rock bands and dead-ends, but I pick my way through and find, to my surprise, an untracked set of chutes to my right just as it rolls over into the really steep section (40-45 degrees). I see light slough marks and a bunch of black dirt on top of the snow, probably from a bomb blast above...but no signs of meaningful motion, so I drop in.

On my second turn, just as I pass the trees, I see that the entire chute has broken loose around me. It's amazing how the brain notices so many things at once, like how the snow around me has fractured into little jagged plates, each 4-6" thick, all the way to each edge of the chute and for some distance behind me; that the chute is about 15-20' wide; and that I have no choice of line at this point, so I really need to start making less turns so I don't get washed through the trees at the bottom.

I turn up the speed. The slough kicked loose from my first couple turns, before the slide, is racing me down, but I am outpacing it with big, shallow GS turns. I slack a little, thinking I've made it.

No, I haven't. Suddenly the wall of snow crashes into and past me. It's taller than I am, and I'm instantly blinded. Fortunately the slope has flattened slightly by this point and the slide is slowing down, so I quickly pop out the front before it can take me for a ride. This time I am not slowing down for anything or any reason, and I'm moving so fast I make it almost all the way up to the high traverse back to Mott.

I'm sorry I don't have any pictures of the actual slide or a better read on the size or depth of the deposition...I forgot my camera that day, and as mentioned, I didn't stop until the area was out of view anyway.

Some things I learned:
-Slab avalanches happen very quickly. The snow fractures and starts moving literally in an instant.
-Slabs can form on very limited, localized aspects based on wind direction and terrain contour. The chutes right next to this one didn't form a slab and didn't slide.
-Slabs are more likely to break loose on aspects that don't get skied.
-Slabs can easily break loose above you, and won't necessarily go from your first turn or ski cut.

I hope this is helpful to someone.

Note: This picture of the area is from a different day in a different season, and is even more filled in than it is now. You can see the typical result of avalanche control, which is that basically everything slides, including both chutes (Pipeline to looker's left, Ramarrah's from center to looker's right) as well as the area between them that I skied.

http://tetongravity.com/forums/attac...1&d=1202023806

makes me feel real dumb happily dropping into many a steep open line at alta right next to an avy bomb thinking "well this is perfectly safe"

Inbound. Out of Bounds. Slides are happening aplenty this winter. I'm glad you kept your wits about you and skied out of the slide. Things might have been interesting if you had your feet taken out from under you and had to avoid trees.

Great post - very helpful. I've skied all that area many times and I'll pay more attention next time in. I too was dropping into places all over Eagles Nest at Alta that had a bomb hole at the top and I was thinking: "Hey, they checked this, we're good to go!" DUMB!!

I think I'll slow down a little and check a bit more from here forward.

Last week, I had Western Airline slide with me as I went down it in the Nest at Alta, and I'd never seen that. Just something for everyone to think of. Once there's 12-18" on top of those rocks, it's basically looking for a way to slide off. I was it. No harm done, other than a serious sphincter strain as I puckered up. But, worth thinking about.

Yikes, I've skied there!!

gotta think next time !

I recall skiing Ramarrah's and riding slough the whole way down. It can be surreal. That slab had to be a freaky experience.
I recall you saying "When I think about pow I slough myself"

Similar?

Quote:

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Originally Posted by Vets

I recall skiing Ramarrah's and riding slough the whole way down. It can be surreal. That slab had to be a freaky experience.
I recall you saying "When I think about pow I slough myself"

Similar?

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In the sense of "inbounds slide", yes, but totally different circumstances and results.

At Rose, the slide was due to a high load of fresh snow that had entirely fallen within the past 3-4 hours, and had not consolidated or bonded to the bed surface at all. Basically it was a loose snow powder avalanche, which built up as I knocked the snow loose with my first few turns. Normally the resulting slough would slide over the existing snow, but since the snow was so fresh and had no cohesion, the slough pulled the rest of the snow down with it, causing the slide.

At Heavenly, the slide was due to an actual windslab that formed overnight in conditions of heavy snow and high winds, and I triggered it all at once with my second turn. It is rare for windslabs to form in a resort and not be triggered by avalanche control: either they slide from bombing, or they are sufficiently well anchored by the snow under them that they stay put.

When we ski "wind crust", we are skiing on a windslab. The difference is that resort slopes typically get skied between storm cycles, and as a result, the snow underneath has enough roughness to anchor the slab. I believe that the area I triggered had not been skied since the last snow on Wednesday: Killebrew is the last area of the mountain to open, frequently only opening two days after a big storm, and the part I was in sees little traffic because it is difficult to get into.

^^^^ Excellent assessment spats.

Nice posts Spats. Glad to hear you came out of it in one piece!