Turnagain Pass

Tincan South Side: We remotely triggered an avalanche near the Snake Pit on the south side of Tincan yesterday. We were digging pits on a low-angle bench when the avalanche released about 50′ below us where the slope rolled over into steeper terrain. The avalanche was about 2′ deep and 75′ wide, running only 150′ before piling debris up on a flat bench. Nobody was on or below the slope that failed. More details here.

Lynx Creek: We received details yesterday of a snowmachine-triggered avalanche in the Lynx Creek drainage on Saturday. The rider noticed the slope cracking around him and was able to ride off the slab without getting buried. The avalanche was 300′ wide and 2′ deep, likely failing on the 1/10 buried surface hoar layer that has been so reactive for the past week. It is worth mentioning that the group had put multiple sets of tracks on the same slope before the last rider triggered the avalanche. Thanks to the rider for sharing the information from the avalanche. There are more details in this observation.

Photo from the crown of the avalanche we triggered on Tincan yesterday.

This layer of buried surface hoar is proving to be quite the persistent problem. There have been natural and human-triggered avalanches on this layer for 8 days in a row now, and it will remain reactive today. With another 0.5-.75″ snow water equivalent (SWE) and strong winds in the past 24 hours, the snowpack continues to see more stress added to this weak layer. Although winds and precipitation are expected to back off for most of the day today, dangerous conditions continue to exist.

As the layer gets buried deeper, it is slowly becoming more stubborn to trigger. However, with this impressive string of human-triggered avalanches, there is no question that it is still reactive throughout our advisory area. Over the past week we’ve seen activity in almost every part of Turnagain Pass– including Seattle Ridge, Eddie’s, Tincan, Sunburst, Magnum, Cornbiscuit, Pete’s North, and Lynx Creek. Now that the layer is around 2′ deep or deeper, it is becoming harder to detect with common travel tests like hand pits. It is also giving fewer warning signs like shooting cracks or collapsing. Case in point- I was unable to find the layer with hand pits along the skin track yesterday in the Tincan trees, and had been stomping around on the top of a convex roll without any results just minutes before we triggered a large avalanche remotely on the same terrain feature.

The snowpack continues to show its potential for making avalanches, and with continued snow and wind the avalanches are only getting bigger. The only way to manage a dangerous setup like this is by avoiding traveling on or below steep terrain.

Wind Slabs: Winds are backing off slightly this morning, but will be picking up again this afternoon. Pay attention to active wind loading later in the day, and be aware of an increased likelihood of natural and human-triggered avalanches on wind loaded slopes as the wind returns.

The1/10 buried surface hoar was still reactive in this pit (ECTP 25). The test result was less important than the fact that we triggered a big avalanche just below the pit. 01.22.2023

In addition to the buried surface hoar layer mentioned above, we are also still concerned with the Thanksgiving crust/facet layer– now buried 4-8′ deep on average. At this point, the layer is so deep that a person would need to find just the right (wrong?) spot to trigger it. Deep slab problems are tricky, since they are so stubborn but if you do find a thin spot where the weight of a person can collapse the weak layer, the avalanche could take down the entire mountainside. Stability tests tell us very little about the layer, and it will almost never give warning signs like shooting cracks or collapsing. They are also notorious for releasing after there are multiple sets of tracks on the slope.

As time goes on it is becoming less likely that a person will trigger an avalanche on this layer, but it is still on our radar for now. Given the widespread persistent slab problem mentioned in problem 1 above, this monster is just one more reason to avoid traveling on or below steep terrain for now.

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