Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 1–2
A storm cycle that began on February 1st has delivered over two feet of snow in some areas of the Selkirk and West Cabinet Mountains, accumulating on a widespread mix of weak layers. Earlier in the season, the forecast advised sticking to sheltered areas for safer travel, but the mountains are keeping us on our toes—those same sheltered zones are now where snow slabs are most likely to sit atop buried surface hoar.
Given the fragile nature of these weak layers, avalanches can be triggered from a distance and may propagate more widely than expected. Avoid the temptation to test avalanche-prone slopes over 30 degrees, even in the trees. The buried surface hoar is like a sleeping giant, ready to wake at the slightest trigger. The safest approach is to stick to low-angle terrain (under 30 degrees) and steer clear of traveling beneath steep, open slopes.
(2/6/2025)
One of the culprit persistent weak grains underneath the storm slab - surface hoar. Before burial, these grains were almost 20 mm in size, they have been reduced to 10 to 15 mm and well-preserved in spots. West Cabinet Mountains. February 6, 2025.
Photo: Chris Bilbrey