Close call at WA Pass 1-5-14

Spent last weekend skiing around Liberty Bowl in fabulous conditions - 11" of new, light wind, temps in the teens, great stability (or so we thought).  We hit many lines all over the basin over the two days and saw no signs of major instability, until our final run to the sleds at 4:30 yesterday.  We dropped into the line all the way to the skier's left from the high bench below "Blue Lake Peak" (i.e., the bench below the B-day tour col), where there is a nice wide low-ish angle pow field (guessing right around 30 degrees) that terminates in trees and a drainage about 800 vertical feet below.  We had skied the skier's right side of that same field twice over the weekend, once before that same morning.  There was also a track from another skier on the skier's right hand side, so 5 total on the field.  On our last run, I traversed at the top to the untouched left side of the field, at full speed, and proceed to rail pow turns unstopped almost to the bottom.  I looked over my shoulder to see where my partner was, and was shocked to discover a fairly big avalanche coming up about 150' behind me.  I was hauling ass at the time, and (lucky for me!!!) the avy was moving pretty slow, so I was able to easily ski down to the left into some trees, outside of its path.  My first thought was that my partner had triggered it somehow, so my main focus was trying to identify any signs of him in the flow as it went by (it lasted a surprisingly long time).  Within a few seconds, my partner skied within sight on the far side of the flow, which was a huge relief.  When the slide stopped a few seconds later, it became clear that I had triggered it, likely when I initially traversed into the field, and had somehow managed to stay in front the entire time, blissfully unaware of what was occurring behind me (pics link below).  A close call for sure.  This experience reaffirmed for me that you can never be 100% sure about stability, especially when dealing with a thin snowpack with some faceted layers at depth.  In hindsight, I'm pretty sure I triggered a wind slab at the top of the field, which is guarded by some large cliffs, and is a significant deposition zone for transported snow. That slab stepped down and triggered a more reactive widespread unstable layer. All of this is just supposition though, as I did not notice any slabby snow whatsoever on the run.  It was "sugar" powder top to bottom.  Be careful out there folks! 

Pics: picasaweb.google.com/1085432858599684297...HtwE&feat=directlink

link to photos doesn't work for me.

Sorry, I updated the link. Hopefully it works now.

Glad you didn't caught up in that.
Don't know the area so the pics don't help answer my questions...
I was wondering about the approximate aspect and elevation of the crown.

Start zone was at approximately 7,000' and aspect is N/NW.

Yikes! Could have been serious; glad you're OK.

Pretty classic, NNW aspect-check, low snowpack-check...

... glad things worked out.

[We will have the trails broken for you by this weekend, unless you perfer total untracked snow/ Blue Peak area skied well today with a foot of new.The waterfall face rock bands lower down on the mountain were a bit punchy and there are still good sized holes around the rocks. Even hit a few.

Lower down, there is a rain/ warming crust transition below the powder that we could feel. 

Up high, Looks  like some  cross wind loading far skiers left below the walls. Could not see the cornice. Tested a steep wind slab over a hard crust and was suprised it did not move, but who knows really it was such a small, small slab.

If I can be of futher assistance,let me know.]

Above was the intel. FSG posted to you. It's from exactly where you skied ! We observed many crown releases on wind affected N,NE,NW aspects below ridgelines as well as sun affected rollerballs and wet slides from 1/3 through 1/4. Probably a good idea to ski one at a time with a lookout or leap frog from safe area to safe area. I took a ride in that same spot , similar conditions a few years back . Glad your Good To Go.   X   

On Dec 26th I was within a 1/4 mile of that slope, perhaps even directly below it. We saw where it looked like a previous group had been a few days prior. It looked like they had triggered a collapse with a one crack forming in the snow. We decided to dig and did one ECT on a ~25 degree slope that did not move at all. I then cut the ECT apart and did a couple of compression tests and had one failure ~8 inches down that went on the second tap from the elbow.
The second test failed at 8 inches on the second or third from the wrist. If your slide stepped down maybe that is the layer. I'm pretty new at this and we didn't stick around much longer to do any more digging. I'm glad to hear you were alright.

On Dec 26th I was within a 1/4 mile of that slope, perhaps even directly below it.  We saw where it looked like a previous group had been a few days prior.  It looked like they had triggered a collapse with a one crack forming in the snow.  We decided to dig and did one ECT on a ~25 degree slope that did not move at all.  I then cut the ECT apart and did a couple of compression tests and had one failure ~8 inches down that went on the second tap from the elbow. 
The second test failed at 8 inches on the second or third from the wrist.  If your slide stepped down maybe that is the layer.  I'm pretty new at this and we didn't stick around much longer to do any more digging.  I'm glad to hear you were alright.

You could be right about the layer. We dug around a bit at the beginning of the weekend, and more thoroughly the weekend before. We were aware of several faceted layers in the snowpack, but we couldn't trigger a reaction with skis anywhere no matter how much we tried (e.g., via ski cuts or at switchbacks while skinning, etc.). That's what made the substantial propagation so surprising. Unstable layers at depth are pretty difficult to predict. Can't believe I'm actually saying this, but I wouldn't want to be a heli guide up there right now.

FSG, (and all Wash Pass skiers):  Good2Go messaged me that his slide "took out" the skin track that you and I avoided on Friday.  I talked with a member of the team that set it on the phone tonight.  I'm agreein' that folks are spending too much time exposed.  Whatever the destination is, putting the original, main uptrack in the safest, then easiest (often not the fastest or most direct) location is going to be more and more important as we see increased use.  Our uptracks here get reused frequently and we don't get many dumps that erase uptracks.  Hopefully we can avoid the Mt Baker syndrome here. 
On Sunday we "met" two new valley transplant couples.  I guess continued mentoring is still "on our plate".

Perhaps this thread should have been in the Weak Layers section and I'll try to post something similar there. The most important point here is the most likely aspect to go wrong: When a skin track is in "threatened terrain" where a skier triggered slide is reasonably possible, AND "line-of-sight" communication is absent. In a remote location, a single team could do this MAYBE. In popular areas it should be a no-go or a "set a new uptrack" condition. If you cannot see if anyone is following your exposed uptrack how can you ski onto the slope that threatens them? If you are following a track into threatened terrain how can you risk having the track-setter bury you?
Hopefully we can get this through to the less aware folks. We have a lot of terrain that fits here in the N Cascades!

mt. baker syndrome is a nice way to term the uphill/downhill interaction and congestion.
b

Very detailed report. Just to recommend, do you measure the slope angle with an inclinometer. And, It kind of sounded like the release was similar to a spring slide - when the release moves slow. This website has the weak layer page.

Important thoughts on uptrack management, TN. Thanks for sharing.

Glad you were skiing fast enough, others might disagree with me but riding as fast as possible for conditions is safer.

I wonder if there was a rock near the trigger point, can't quite tell from the photo. Perhaps there was a thick hoar layer surrounding a rock, it could easily propagate from there even thought pits weren't very reactive.

Or perhaps the snow cover was just thinner up at the top of that side of the run, thus making it easier to trigger on weak layers that were more deeply buried elsewhere?

At my home mtn, Mammoth, CA, the very top is similar to this spot. There are rocks above, and the snow accumulates below the rock outcroppings (as the snow doesn't stick to the rocks). The main run is named Climax. Due to the possibility of a climax avalanche, usually from a rain event prior to a large snowfall. In Feb, '86 a 22 foot fracture was measured at another apex of the mtn !

Have any of you skied the south side of Blue Pk? Quite a few years ago we had yet another shallow early season snow pack, I don't remember if we'd had any cold temps but most likely so given the eastslope. We'd skied Madison Ave almost to the valley bottom, had climbed back up and were sitting at the col having lunch and trying to decide if we were going to ski it again. One of our group walked over to just below Blue Pk and started to dig a pit. That set off the whole slope from just a few feet below where we sat - wall to wall, to the ground and all the way to the valley floor.

This year reminds me of that year. Watch out.    

This run has a series of fall line ribs separated by troughs that run up to the rock face. Not much higher is the ridge line .This spot gets quit a bit of multi directional wind. Where the upper edge of the snow deposition meets the rock face there is usually a layer of ice . If you traverse high on this slope you cross rib trough rib trough etc. When I triggered this slope I was the fifth one down. It's a real sleeper . Hope this helps. X