Multiple small slab releases in Dogleg Chute, South Maggie's Peak

My partner and I skied the Dogleg Chute, which drops into the Cascade Creek canyon from near the summit of Maggie's Peak South.  We were aware of moderate instability on our intended descent due to wind loading and decided to go ahead and ski it, staying aware and making the best use of terrain to minimize the hazard.  In the course of descending the route we released five small slab avalanches.

All of these slides were similar in one primary way: they were all in a generally three to eight inch deep (maybe up to 10" in a few places) layer of new snow, of which we think maybe three inches was direct snowfall and the rest was additional wind loading.  And they all released and slid at the same old surface, which we presume was the previous surface layer before saturday/sunday's storm.  That surface had a good deal of texture to it, but clearly the new snow had not bonded entirely with it for reasons of temperature and moisture (and inadequate time elapsed).

Most of the slab releases were expected and mitigated by having and using a planned escape route, but one almost caught me as I ended up riding on top of it for a few moments too long (this was the only one that cut above the skier rather than right on his tracks).

Arriving at the top of the chute, we noted cornices fairly continuously along the lip of the chute, overhanging anywhere from a foot in most places to two or three feet in one windier spot.  Staying well back, we did some belayed cornice cutting and got one five or six foot wide area to crack about 30 inches back from the edge.  However, it did not just crack and go, it took quite a bit of jumping and pushing to get it to give up its grip on the older cornice buildup below it.  Eventually we did get that block to break and slide down the chute, wanting to see if or where it might trigger anything else.

I should explain that in no way was the whole chute continuously loaded.  There were vertical stripes that had already slid, and there were vertical stripes and sometimes cone-shaped deposits of wind-loaded snow.  So rather than being continuously endangered we were able to work our way from one area of safety to another, taking a few fun turns in the wind-load snow when either its angle was less than average or in spots where briefly there was no alternative.

The first release was as I skied first into the chute, taking a slightly descending traverse line in.  It did not release upon impact with the snow as I entered, but as (and somewhat after) I cut across twenty feet of snow.  I had figured that area might go (but shallowly, like it did) and I was taking an intentional line to safe trees on an area of minimal slope.  This release was around fifteen feet wide, three to four inches deep, and probably about 10 feet long.  The side walls (as with all of the following slab releases) were indistinct, not at all clearly cut.  The crown was also not really distinct because it coincided exactly with my ski track.  But I was fairly sure that the depth was three to four inches.  This snow broke up after sliding out of its starting area, and ran perhaps 200 feet.  This release was on an angle of approximately 42 degrees.

The next was a smaller one triggered by my partner, also in a spot that we discussed and thought might let go.  He was setting his line to avoid exposure to hangfire above him as well as to eliminate any possibility of going over a rock band below in case he did lose his footing.  He took a diagonal line across some wind deposited snow and a slab of it tore out and slid.  I didn't get a good look at this one, but I think it was roughly five inches deep and 10x10 feet, running 100 to 200 feet, and occurred on a slope in the high 30-something degree zone.

We came to a spot that required either some rocky maneuvering and sideslipping or a short mandatory straightline, after which the skier would impact the soft snow in the next section fairly hard.  My partner chose the latter and straightlined about ten or twelve feet then turned to scrub speed, and set off the largest of our several slab releases.  This one too did not release upon initial impact, but it went once he had cut across about fifteen or twenty feet of it.  This was around roughly 7800'.  Here too the sidewalls were totally indistinct, not at all clearly defined, and the crown coincided with his ski track so it was hard to measure, but we think it was six or eight inches.  This was on a slope probably between 35 and 40 degrees.  I think the length of the slab that release was again roughly equal to its width, but it's hard to say for sure.  This one rapidly gathered enough momentum to travel all the way down the remainder of the chute, from around 8200 feet to the end around 7200 feet.

My partner had one other small release during the descent which I did not see, but I believe it was similar to #2, the other most minor one.

My one other release, and the only one that partially caught a skier, was around approximately 7400'.  This was the only slab with a crown occurring above the skier.  I'm not sure but I believe it cut around six feet above me; possibly on my previous turn as I made the turn after, but I don't know.  In any case the moment I noticed I was riding on a moving slab, I peripherally saw that roughly six feet of it above me was moving before I concentrated on getting off and out.  I skied laterally off of it to a safe and stable spot, but by the time I finished doing so one of my ski tails had sunk through the breaking-up slab and had started to get pulled under by the moving snow.  I kind of willed myself forward harder and got a grip on non-moving snow and avoided too much of a ride, but I think I hyperextended my knee a bit.  Lucky to get by with only that minor injury.  This one released on the lowest angle of all of our slabs.  It was barely 30 degrees if that, might have been mid to upper 20s.  Maybe it's significant that the lower we dropped in altitude, the more these slabs were willing to break and slide at lower and lower slope angles.  I don't know.  In any case this was our lowest release and it broke and slid on the lowest angle slope of all of them.  So anyway, this one was also the thickest, probably around 8 inches thick in places, maybe only 6 in others.  It was about 15 feet wide and long, and only traveled around 150 feet before it just stopped by friction and low slope.

All in all we had somewhat more activity than we might have guessed in the chute, but none of the releases were particularly surprising or unexpected.  We would not have chosen this route on this day if we felt there was potential for more extensive (and in particular, deeper/thicker/wider) slab breakage.  We're aware that three to eight inches can kill you if things go drastically wrong, but we were willing to manage that by terrain interaction.