Continental

Avalanche problems

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1.5–3

  Persistent weak layers of faceted snow continue to be found at a variety of depths in our snowpack. For the last several weeks, there has been little stress on these weak layers, but colder, drier weather has been promoting weakening of the upper snowpack in many areas, especially where coverage is thinner. Warming ambient temperatures today and into the future may change the character of slabs overlying these weak layers, with the potential for increases in hazard. This will be especially true on sunny slopes, where solar radiation could soften the surface snow. Small loose snow avalanches triggered by the sun are a good indicator of increasing hazard. These smaller slides could be followed by deeper releases as warmth penetrates the upper snowpack. 

   Variability over short distances is making assessment challenging this season. There is a wide range in snowpack structure out there due to frequent wind redistribution of snow this winter. Poor snowpack structure exists in specific areas where weak facets are sandwiched between layers of slabby wind-affected snow in the upper 2 feet of the snowpack. Slope-by-slope assessment is recommended to determine the snowpack structure in your area. Digging and probing into the snow in many areas while you travel is the best way to do this. Layers of hard snow over weak snow will indicate potential instability. 

  Weak snow becomes more widespread in the continental zone. Any areas with firmer slabby snow on the surface should be suspect since the underlying layer will be very weak. 

  A recent skier-triggered avalanche at 4,000 feet on a west aspect near The Books is a clear reminder that instability is still lingering where stiffer snow overlies facets, despite very little meaningful weather change in recent weeks. Users can reduce their risk by practicing good travel habits, such as exposing only one person at a time to avalanche terrain, keeping a close eye on partners, and choosing simple terrain with clean runouts.

  Wet Loose: If the sun comes out today, there will be an increasing chance of wet loose slides on sunny slopes. Warming surface snow on top of weaker facets is expected to contribute to this hazard while also increasing the chance of a deeper slab releasing. Keep an eye out for moistening snow, rollerballs, small loose slides, and cornice fall that will indicate an increasing hazard. 

  

• 

  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Unlikely

  Size

  2–3

  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 but high-consequence problem most likely to be triggered 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.