Turnagain Pass

• Seattle Ridge – We received multiple reports of a possible remote triggered avalanche south of the Seattle Ridge uptrack. Currently we are uncertain whether reports are from one or two avalanches in the same area. One report stated that the avalanche released at 2500’ and was about 18” deep by 60’ wide and ran approximately 400’ (photos here, more details here).

Seattle Ridge slab avalanche 11.26.21. Photo from anonymous

• Tincan Common – Skier triggered soft slab avalanche on skiers right hand side of common bowl on Tincan. This avalanche was about 24″ deep and was triggered from lower angle terrain above the crown.

Tincan Common slab avalanche 11.26.21. Photo from Matt Dietrick

• Hope area – this is outside our forecast zone, but the conditions in this location appear to be similar to the Summit Lake area. The avalanche was triggered on a ridgeline with a firm wind slab over faceted snow or possibly buried surface hoar. Skier had previously descended near this same slope but triggered it while climbing back up. They were caught and carried about 400′ and able to arrest on the bed surface, but are ok.

Hope area avalanches, an old windslab over a persistent weak layer from 11.26.21. Photo from anonymous

• Lipps Glide Avalanche – Observations of glide releases have slowed down in the past few days, but this new release was spotted yesterday on the south face of Lipps. We don’t know the exact release date but it was between 11.21.21 and 11.26.21.

Photo 11.26.21, exact release date unknown

Our primary concern today is persistent slab avalanches which could be triggered on a variety of weak layers (details here and here) that are becoming more active as the 20-34” of very light new snow from this week gradually settles into a more cohesive slab. These slabs can be 2-3′ deep and have the potential to propagate across an entire slope. Triggering an avalanche is more likely in areas where the wind has transported snow to create a firmer slab. The most recent pulse of snow came in on Wednesday (~10-12″) with no wind, which makes it very hard to see where the prior storm snow has been redistributed by wind. Assessing the slab character of each slope by travelling off trail and looking for red flags, such as collapsing (whumphing) and shooting cracks, is important to evaluate conditions today.

We recommend keeping a conservative mindset today because of the weak snowpack structure and a high level of uncertainty about where conditions are unstable. Persistent slabs can be tricky because it is not always the first person on the slope who triggers an avalanche. We have observed remote triggering in avalanches yesterday and expect similar conditions to remain throughout the weekend. If you want to keep it safe today, stay on terrain with less than 35 degree slope angle and pay attention to steeper slopes above you. It is important to travel one at a time in terrain above 30 degree slope angle and spot your partners to minimize the consequences if an avalanche is triggered.

Shooting cracks in new snow over faceted weak layer from 11.25.21 on Seattle Ridge

Snowpack summary from Sunburst on 11.26.21

Summit Lake Area – An avalanche reported in the Hope area yesterday seems to line up with conditions observed in Summit Lake recently. This avalanche was a hard wind slab over faceted snow that released along a ridgeline. Even though this is outside our forecast zone it is worth noting if you are planning to travel in Summit Lake today, where the new snow from this week only added up to 3-6” but old wind slabs could continue to be a problem.

Glide avalanche activity has slowed down in the past week, but we observed a release on the south face of Lipps sometime in the past few days. This is a reminder the glides are still active in our area. It is key to minimize time underneath glide cracks as they can produce very large and unsurvivable avalanches. They can also be a hazard to fall into on skis or snowmachines and are harder to see in many locations because of the recent light storm snow.