Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1–3
24 to 36+ inch slabs rest over two buried weak layers of concern. The first layer you'll encounter is a layer of 1mm Near-Surface Facets buried 60-70cm from the surface. The second layer is 2-3mm large-grained facets buried 80-100cm down. We have been able to get results on both layers in our long column tests from easy to moderate force. Due to the depth and length of time since our last loading event, it's getting more difficult to trigger an avalanche. However, when or if you are able to, our long column tests have illustrated an alarming ability to propagate, with slabs collapsing and shooting off the column with little resistance.
The most likely areas to trigger these avalanches are on northwest through east aspects near and above treeline in areas where the slabs are thinner and you are more likely to impact these buried weak layers. The size of these avalanches could approach D3 in size above treeline or on well-connected open terrain. Pay attention to signs of instability such as shooting cracks and audible collapses. Stay out of terrain steeper than 35 degrees.
West and southeast aspects saw significant solar effects on Jan 2 and 3rd and have since formed a melt-freeze crust that is reducing the likelihood of triggering an avalanche. However, there is still poor structure on these aspects, so don't let your guard down just yet.