The Bottom Line: Overall we are still observing lingering poor structure in the deeper snowpack. Having just dropped down from Considerable danger, we are in the mindset of “scary moderate.” Over the last week, the NW and N winds blew hard, loading up SW through S through E aspects with wind slabs and cross-loading other aspects, gullies, and features. Most alpine areas are going to be a mix of sustrugi, hard slabs / wind board, and slabby powder in protected areas. Variability in these surface wind slabs is high. The most dangerous areas will be wind loaded solar aspects steeper than 32 degrees where you may still find tender slabs resting on weak old snow. Likewise, cross-loaded gullies will have wind slabs and pillows that could take you for a nasty ride. Some nice softer snow remains in the trees.

 

 

 

 

Wind slabs can be avoided by sticking to sheltered or wind-scoured areas. Also from the wind, cornices will 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. 

 

Buried Surface Hoar Layers (These layers have become less reactive in snowpits, but smaller slides could still step down and trigger them):

• Jan 25th melt freeze crust is 1-2′ deep (with recent winds and snow, there is a lot of variability on depth of this widespread layer) sitting on top of it are near surface facets, and buried surface hoar from Feb 1-4.
• January 10th surface hoar is now buried about 3-4 feet deep. Reports of remote-triggered activity on this layer Jan 27-28.

 

Feb 24- Haines Pass, W aspect, 2350′ Pit pictured below produced a ECTX and a PST 58/100 end down 70 cm. Photos of buried surface hoar are from the Jan 10 layer down 70cm.

   

 

Feb 17- Haines Pass W, SW aspect. 2500′ The pit pictured below produced a ECTP19 down 40cm on facets under a thin ice lens/Jan 25 layer.

 

Graphed results from pit above.

 

 

Feb 17- Haines Pass tree line 2500’ S aspect ECTP24 40 cm down, below Jan 25 crust

 

Feb 17- Haines Pass W, SW aspect. 2500′ The pit pictured below produced a ECTP19 down 35cm on Jan 25 crust/Feb 1-4 facet interface

 

 

 

Jan 22- Propagating result down 45 cm, 2,300′ SW-aspect, 7-Mi Haines Chilkat Pass.

 

 

Photo taken on Jan 12 of Surface Hoar on a W aspect near treeline in the Haines Pass.

 

 

 

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 (especially as temperatures rise). 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.

Deep weak layers under strong layers are persistent in the pass. A wide safety margin is necessary. This setup could produce avalanches that break wider than expected, and are most likely to be triggered from shallow trigger points like rocks or small trees or a smaller slide that steps down to these lower instabilities.  You could ride the same slope numerous times until that right spot produces a large destructive slide.

 

Old Melt Layers and Crusts:

• The Dec 31 surface hoar layer is present in the Transitional and Pass zones, about 4+ft deep. This layer has been active in pits, and caused some natural avalanches in early January
• Cold temperatures and a shallow, wind scoured early season snowpack created conditions for depth hoar growth.
• A buried persistent weak layer about 6+ feet deep (The “Big Warmup” Layer, Formed Nov 17th) is still a concern. Numerous natural avalanches observed 1/27 likely on this layer.

 

Feb 17- Haines Pass W, SW aspect. 2500′ Faceted clusters found near the ground

 

Photos shows 6-9mm advanced depth hoar at the ground down 180cm with ECTP 25 down 80cm on facets below a crust in the Haines Pass Zone at 4,000ft on a NE-aspect.