Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 2–3
Recent Avalanches: Multiple remotely triggered avalanches were reported in the Lost Lake area on Friday. Large avalanches were seen on mountains surrounding Seward over the weekend including peaks that are closer to Lost Lake. We suspect these are from a layer of surface hoar that is responsible for many avalanches in Turnagain Pass.
Avalanche conditions remain dangerous despite the quiet weather. With partly cloudy skies, light winds, and more daylight for the next few days, mountain travel will be easier. This is worrisome as an avalanche forecaster as we know there is a buried weak layer capable of producing large and dangerous avalanches. While Andrew was out at Snug/Lost Lake on Tuesday he experienced collapsing snow and shooting cracks that propagated around 100’ from his snowmachine. These are clues telling us that the snow is still very unstable. Multiple avalanches have been remotely triggered meaning that people traveling on lower angle slopes are triggering avalanches above them or on slopes adjacent to them.
The main point is this type of avalanche (persistent slab avalanche) can still be triggered. This Valentine's Day weak layer is buried more deeply now after Sunday's foot or more of snowfall, which means the potential size of avalanches are larger. It can also mean it's tougher to trigger and so those hidden thin spots end up being the places we do trigger these slabs. The weak layer has been found on all aspects above 1,500' and is the perfect setup for remote triggered avalanches. This is a case where no warning sigs may be present, meaning no whumpfing or cracking in the snow around us; a really tricky situation as all can seem just fine until it is not. Because this layer is so challenging to assess, the safest option is to make conservative decisions and stick to less consequential terrain away from steep overhead slopes.
