Large deep slab avalanche triggered remotely. Northeast facing aspect.
snow density changing rapidly during day due to sun making snowpack heavier.
Note: see https://www.flatheadavalanche.org/observation/scary for more details about the avalanche itself.
From a later email by the party:
Our plan was to ski the spur staying out of the open bowl following trees down to knob. We knew we needed to ski one at a time and stay on spur. We pulled skins. I stomped my ski on top of ridge. We heard and felt big whompf w my stomp. Then we heard and saw avalanche below. We backtracked along ridge to lower angle slope w trees. Skied down to look at bottom of debris path...That ski brought us back below the avalanche debris path. We then saw [the forecaster's party] skinning up the debris path about midway....We returned to trailhead parallelling our morning ski track in. Not best terrain for skiing and clearly not our plan for day. Our original plan had been to do a loop from Crystal to Wahoo. We had done that midweek and had some great skiing. We were familiar w the route and objective hazards. Prior to the avalanche Saturday we had not felt any settling skinning in or sounds. I was definitely aware that we had more snow than earlier in the week and as the day progressed was observing how the weight of snow was increasing w air temps and solar radiation. I had also read the FAC bulletin that morning and was aware there was a deeper unstable layer particularly on north faces. In fact, we talked about it while standing on ridgejust before avalanche. Even discussed how far down we might have to dig to find unstable layer. So glad we were cautious w guard up rather than getting lured to charge in to what looked like great powder skiing.
...We needed to arrive at decision to abandon our route objective prior to avalanche. Lot of research lately on group decisions or lack thereof in backcountry ski accidents. We could have easily fallen into that trap letting a stronger voice keen on completing route objective lure us all into continuing. We did not fall victim to that behavior electing instead to dial it back and use our new data to change our route plan. Great day out and another valuable experience to add to the personal library of self preservation
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