The Bottom Line: A new NW wind event is ongoing, and with plenty of snow available for transport, we are seeing active wind loading from treeline and up. These fresh wind slabs will be reactive to human weight, and anywhere from 1-3ft thick in wind loaded areas. They are being held up by weak storm snow and facets. Human triggering is likely on slopes steeper than 30 degrees. Be especially careful to avoid steep, wind loaded, sunny aspects.

Photo: Example of a wind loaded slope with a wind slab avalanche that stepped down to deeper persistent layers below. This one was probably triggered by cornice fall. Photo from Flathead Avalanche Center.

Wind slabs can be avoided by sticking to sheltered or wind-scoured areas. Also from the wind, cornices might be unsupported, scoured, and weak. Tread carefully around them and limit your exposure to slopes below them. A cornice drop could cause a slide, with potential for a step down.

The severe consequences of our avalanche problems remain, due to deep persistent layers. Be hypersensitive of terrain- it is an active way to manage our exposure to the risk of an unlikely but high-consequence deep slab avalanche.

When on or near avalanche terrain, be diligent on terrain selection, group management, and human factor.  Travel one at a time or with enough spacing so that only one person is exposed to an avalanche path at any one time. Be prepared for an avalanche that could step down to deeper instabilities, creating a slide that could break very wide, and take out all the “safe” zones on a slope. Be extra careful not to group up in places that an avalanche can reach. 

When seeking out wind protected zones, remember that wind-protected pockets may be harboring weak, buried surface hoar layers. Protected means preserved. 

Jan 25th melt freeze crust is ~4-5′ deep sitting on top of it are near surface facets, and buried surface hoar from Feb 1-4.

Snow pit from Feb 22 in Lutak (NE aspect 1800ft) showing persistent weak layers below the snowfall from Feb 10-15.

Cornices have become very large and weak. They are undercut, overhanging, and slowly sagging as they grow. Strong sunshine and increasing winds will put a lot of stress on these dangerous beasts. Stay way back from any snow ledges or cornices on ridgelines or summits. Some may fall naturally, so do not travel below them. More likely will be human triggering of cornices from above. When a cornice fails, it will break way further back on the ridge than expected and take most of the flat terrain out with it. Any cornice falls are likely to trigger very large and deadly deep-slab avalanches. Consequences are very high right now!

An unlikely to trigger, but high consequence deep slab layer remains. The “Big Warm-Up layer” from Nov 17th is not to be forgotten about. Although currently dormant, a smaller slide triggered on the upper snowpack could step down and trigger this deadly beast.

Lutak, Feb 4 PST 70/130 End down 130 rounding faceted polycrystals.