Wind Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1–2
2-3" of new snow fell overnight in this zone and an additional 3-5" are expected to fall this morning. Moderate to strong gusty winds blowing out of the W are transporting this snow and building 1-2 foot thick drifts and slabs. These slabs will be largest and most reactive in exposed middle and upper elevation terrain. Look for them near ridgelines and on the sides of mid-slope features like ribs and gullies. In the steep, rocky terrain of the Sawtooths, slabs commonly form underneath large cliffs and on aprons below couloirs. Strong winds can build slabs in unusual locations, keep your eyes peeled out there. Dune-shaped drifts and textures on the snow surface like waves and ripples are signs that the wind has been at work, as are fresh cornices along ridgelines. Cracking and collapsing are clear indicators that you've found an unstable slab. Consider the consequences of being swept off your feet and carried through the terrain you are in. Even small slabs can carry high consequences if they drag you through trees or over rock bands.
Fresh slabs are building on a variety of weak layers that developed over the past several weeks. Avalanches that fail on these weak layers will break wider and may be more sensitive than you might expect a "simple" wind slab to be. These layers appear to be at their worst on slopes that directly face the sun where crusts+facets are buried. Slides failing on crusts can pick up speed quickly, thanks to the slick crust underneath.
ADDITIONAL DISCUSSION: In terrain steeper than about 35 degrees it will be possible to trigger small loose snow avalanches involving both the new snow and the weaker facets underneath. At lower elevations, temperatures have remained above freezing and the upper snowpack is warm and moist. There, these loose snow avalanches will have a wet character. Loose snow slides are unlikely to bury you, but may be able to knock you off your feet and send you downslope.