Summit Lake

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1.5–2.5

  In addition to the alarming setup described in Problem 1 above, it is also likely that a person will be able to trigger a large wind slab avalanche at and above treeline. Easterly winds will slowly start to calm over the next 24 hours, but they are currently still at work moving snow into reactive slabs at and above treeline.

  Be on the lookout in the typical locations (below ridgelines, convex rolls, and in steep gullies), as well as unusual locations further down slopes than we often see. These avalanches can be anywhere from 1' to 5' deep or deeper, and have the potential to step down and trigger a much larger avalanche failing on that deeper weak layer described in Problem 1.

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  2–3

  Recent avalanches: We observed a widespread natural avalanche cycle on Friday, including very wide-propagating avalanches on Fresno, Raven, Butch, Tri-Tip, Templeton, and Summit Peak. There were multiple very large human-triggered avalanches in Girdwood, Turnagain Pass, and Seward, but none that we have heard of so far in the Summit Lake zone.

  The stormy weather has passed, for the most part, but avalanche conditions remain very dangerous. It is still very likely that somebody will trigger a very large and destructive avalanche from flat terrain connected to steeper slopes. We are seeing clear signs of unusually dangerous conditions, including people triggering huge avalanches. Yesterday we triggered a collapse in Turnagain Pass and felt the snowpack drop several inches right below us. This poor snowpack structure is very similar in the Summit Lake zone. Don't get fooled by the quiet weather—conditions are primed for an avalanche accident.

  The current setup is different from what we normally deal with. The weak layer of faceted snow, now buried 2 to 4' deep, will not heal in a day or two like it often does after large storms. This layer will lurk under the surface, waiting for a person to trigger a very large avalanche, for an unusually long time. As we get further out from the last loading event, this layer will slowly become more stubborn and may allow several tracks on a slope before someone draws the unlucky straw. It will heal eventually, but that will take much longer than usual. 

  For now, an unusually dangerous snowpack means we are being unusually careful with terrain management. When the snowpack is complex, we keep our terrain simple, avoiding traveling on or below steep terrain.