Summit Lake

Avalanche problems

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  It has been weeks since we have seen an avalanche on the layer of buried surface hoar in Summit Lake. However, red flags of whumpfing and shooting cracks have been observed recently in a few different places including Raven's Ridge and John Mountain. This is telling us there are places where this weak layer is intact and and avalanche could be triggered by a person. Because the layer is only buried about 1' deep in many places the avalanches should be smaller than they have been in Turnagain Pass. We think the most likely places for this to occur is above 2,000' in areas sheltered from the wind like where there are sparse trees or just above treeline. 

  This type of problem is especially difficult to assess. Hand pits and snowpits can be useful, but in Turnagain Pass they have been unreliable as a way to make a decision to ride a steep slope because a stable test result was located 100' from a large avalanche triggered by a person. If venturing into steeper terrain, look for slopes without consequenses like rocks or trees. Also, ensure that the slope fans out at the bottom with no gully features that could allow debris to pile up.

  

• 

  Glide Cracks

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2–3

  Large temperature swings this week have expedited the transition to a spring snowpack. This transition will continue for many weeks and brings a great deal of uncertainty. There are many factors that affect the timing of warming and melt water infiltrating a snowpack, which leads to many avalanche problems especially wet snow problems. This makes forecasting the timing of these problems difficult and an extra margin of safety is a good idea. Because we have this especially dangerous weak layer described in problem 1, the safest option is to stick to low angle slopes as our extra margin. An extra margin of safety can also include being critical of safe spots, ensuring we are watching partners, and choosing slopes without consequences.

  Wet loose avalanches have been releasing naturally as the snow heats up in the afternoon. The forecast is for the clouds to clear out today, but this problem is likely to occur even if some high clouds stick around. Roller balls are the indicator that wet loose avalanches could be triggered by a person. Wet snow is heavy and difficult to escape especially when a lot of it becomes entrained. 

  Cornice fall has been occurring naturally as well with warming temperatures. In some places (most recently in Portage above the Shakespeare Glacier) these large triggers have produced slab avalanches beneath. Keep an eye on cornices if you are passing beneath and give them plenty of room on the ridge.