Summit Lake

Problèmes avalancheux

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1–2

  The Summit Lake snowpack harbors the same weak layer of buried surface hoar that is causing many human-triggered avalanches in Turnagain Pass including a fatal avalanche on Saturday. Two observations came in over the weekend from Summit Lake reporting collapsing/whumpfing (on John Mountain and Raven's Ridge) and shooting cracks (on Raven's Ridge). These collapses occurred on low angle terrain, but a collapse is a failure of a weak layer that would produce an avalanche if it was on a steep enough slope. These groups chose to enjoy riding some low angle terrain on their descent. Collapsing and shooting cracks are red flags that mean the snowpack is sensitive to failing with the weight of a person.

  The group on Raven's Ridge dug a snowpit and got an unstable result (ECTP4) on the buried surface hoar 1' below the surface. In other locations in Summit Lake we are getting stable snowpit results, but this layer is proving to be completely unreliable with snowpit results. Human-triggered avalanches are occurring in Turnagain Pass within 50 to 100' of stable snowpit results. We are relying more on the knowledge that poor structure exists (weak layer of buried surface hoar beneath a slab) and that red flags are occurring to inform our decision making. If you are venturing into steep terrain look for slopes that fan out at the bottom with no terrain traps like gullies or creeks where snow could pile up. Stick with safe travel protocols like choosing low angle terrain to ascend and travel one at a time in terrain steeper than 30 degrees.

  

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Unlikely

  Taille

  1–2

  Winds were strong enough on Saturday evening to make some wind slabs in the upper elevations. There may be a stubborn one out there that could be triggered in steep terrain. Wind slabs can feel hollow and if you poke them you will find stiff snow over softer snow. An old wind slab may let a person get way out onto a slope before releasing so watch for hazards below and be ready with an escape plan. East wind today is forecast to pick up later this afternoon and will likely create some fresh wind slabs that will become a problem tomorrow. 

  Other hazards today include cornices, which will continue to fail as we head into warm springtime conditions. Give cornices space on the ridgeline and watch for them from below. Glide cracks continue to creep downhill and can release into glide avalanches which take the entire season snowpack with them when they go. Avoid travelling underneath these unpredictable hazards whenever possible.