Turnagain Pass

A LOT of avalanche activity occurred yesterday on the southern end of Seattle Ridge. Some of these avalanches were very large with crowns up to 10′ deep in wind loaded areas. No one was caught in any that we know of. The weak layer in most appeared to be weak faceted snow near the base of the snowpack.

Backside of Seattle Ridge (Triangle Bowl/-3 Bowl):  A group of two snowmachiners remotely triggered a large slab avalanche on a northerly facing slope from ~100′ away (photo below). No one was caught. This avalanche likely sympathetically triggered at least two more avalanches lower and across the bowl. Additionally, these riders remotely triggered at least two very large slabs in the bowl to the south when on the ridge (also pictured below). Report from group HERE and our report HERE.

Backside of Seattle Ridge (Widowmaker Slide Path):  A relatively smaller slab was triggered by a person yesterday afternoon. Unknown what mode of travel or any other details at this time.

Front side of Seattle Ridge:  Several slabs pulled out in the steep gullies just across the motorized parking lot. We are unsure if they were triggered by riders along the ridge or natural from the very end of the strong winds the afternoon before (on 1/4/23). Let us know if you saw these on Wed, Jan 4th.

Summit Lake area:  Many large natural avalanches that released Wed, Jan 4th, during the strong winds were seen yesterday. See the photos HERE.

Large slab remotely triggered by 2 riders in Triangle/-3 Bowl yesterday morning. 1.5.23.

Looking up into Triangle/-3 Bowl at the remotely triggered slab on the right and sympathetically triggered slab on the left (SW aspect), a much larger slab also released out of view to the left of the photo . Photo by riders involved, 1.5.23.

Large slabs remotely triggered by the riders along the ridge. This is the bowl directly south of Triangle/-3 Bowl. Photo by Jon Davis, 1.5.23.

Slab that was triggered yesterday afternoon on the Widowmaker slide path. 1.5.23. 

Five slabs on the front side of Seattle Ridge. Unknown trigger. 1.5.23.

Close up on the slab on the front side of Seattle that is furthest to the left in above photo. 1.5.23. 

With another quiet (and sunny!) day on tap, triggering a large avalanche breaking in buried weak layers, anywhere from a couple feet deep to 8 or 10′ deep, is the main concern. To put it simply: we can’t have that many big avalanches triggered by two snowmachiners on the first nice day after a series of storms and not realize we have a serious HEADS UP snowpack.

This can be a tough situation because no signs of instability may be seen before a large and dangerous avalanche is triggered. There also could be areas that are much less likely to avalanche, but it is nearly impossible to really know what slopes those are and what ones are not. There has not been a lot of traffic (that we know of) outside of the ‘typical’ high use areas (i.e., the common bowl on Tincan and the front, westerly, lower angle slopes of Sunburst) in the last few days. I ‘glassed’ over to the non-moto side of Turnagian yesterday afternoon and did not see many tracks and no avalanches; you can only see so much from binoculars however.

Some points to consider for getting out in the backcountry today:

• Thin areas in the snowpack are the most likely to avalanche. This includes upper elevations that see a lot of wind, the south end of Turnagain Pass, Johnson Pass, Lynx Cr, Silvertip and on to Summit Lake. Girdwood Valley may also be more of a problem spot.
• Elevations near 2,500′ and above are most suspect. Debris may run into the lower elevations. The widowmaker slab (2,300′) may have released on a crust formed during the Xmas storm, which is about 3′ deep in this location.
• Watch for other groups when traveling along ridgelines. If an avalanche is triggered from a safe area along the ridge, it could threaten another group that could be below you.
• Cornices are large and re-shaped. Be sure to give them an extra wide berth. They could also trigger a large avalanche below.
• To avoid this issue all together, we can stick to lower angle slopes (30 deg or less) with nothing steeper above us.

We investigated one of the remotely triggered avalanches yesterday and found the weak layer to be facets at the bottom of the snowpack. At this elevation (3,000′) and generally above 2,500′ no crusts were found in the slab from the Xmas or New Year storm. What we think was the Thanksgiving crust sat just above the faceted snow that was the weak layer – see crown profile below in a shallow area in the slab.

A look at the crown of the Triangle/-3 Bowl avalanche on a northerly aspect at 3,000′. This area was the safest to access and was in a very shallow section of the snowpack. 1.5.23.

Between 2,500′ and 2,000′ the Xmas storm created a crust with weaker snow on top that could be creating a weak layer closer to the surface. This layer was the likely culprit in the Widowmaker avalanche. Although this concern is in a small elevation band, it is looking like another layer we are concerned with. In short, there are several concerning weak layers that have been loaded by the storms over the past 2 weeks that have proven guilty.