Continental

Avalanche problems

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2

  So far, Valdez has received just a few inches of fresh snow from the current storm. Storm intensity is expected to increase today, producing a foot or more of fresh snow in areas that remain below freezing. As the storm progresses, warming temperatures may create top-heavy storm snow, adding to instability. It will be possible for a human to trigger small avalanches in specific wind-drifted areas at the start of the day. The hazard will become more widespread with human-triggered avalanches up to a foot deep becoming likely as snow depth increases over the next 24 hours.  

  Wind slab: Recently, hard windslabs that are sitting on top of weak faceted snow have shown lingering reactivity. It may still be possible to trigger a stubborn windslab in isolated areas where the slab is sitting on weak unconsolidated facets. This problem will be hard to assess as new snow disguises the old wind slab. You can use your pole or probe to assess the underlying layer. 

   

   

   

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2–3

  There is a small possibility that a person could trigger this problem in areas where the slab is thinner and more sensitive. There will also be an increasing possibility of a storm slab or windslab avalanche stepping down to this layer. Hardslab avalanches 2-4 feet deep could propagate long distances and be very destructive. This problem is not likely to show signs of instability before an avalanche occurs

  We continue to seek understanding of the distribution and sensitivity of the 1/26 weak layer. There is continued uncertainty about this layer, but we know it is still out there in specific areas and has produced several avalanche cycles over the last month. The last wind event stripped the snowpack of the overlying slab in exposed areas while forming thick windslabs on top of the layer on leeward terrain features.  Expect this problem to be a concern on specific previously windloaded slopes. Accumulating snow loads and increasing temperatures are expected to increase stress on this buried weak layer, where it exists. 

   

• 

  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Unlikely

  Size

  2.5–3.5

  Weak snow near the ground is increasingly common as you move North through our forecast zones, with the Continental zone being the most concerning. Although it still remains unlikely to trigger this layer, areas that have been scoured from strong northeast winds now have a shallower snowpack making this layer closer to the surface and potentially easier for a rider to trigger.

  This is a low-likelihood, high-consequence problem—especially in steep, rocky terrain and areas where the snowpack is thin or scoured. Triggering this layer directly is unlikely at this time, but avalanches that start in the upper snowpack could step down to the basal weak layer.  There is a high degree of uncertainty regarding the poor structure at the base of the snowpack.  What we can be sure about is that this layer is less of a concern in the Maritime zone and more of a concern as you move towards the Continental zone where the snowpack is thinner and the weak layer is more developed. 

  Watch for thin spots near rock outcrops, scoured features, and along ridge tops. Wind loading adds stress to these shallow areas, and we don’t know where the tipping point is.