Summit Lake

Avalanche problems

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2

  Recent Avalanches: A slab avalanche was reported on Wilson Peak on Friday, and several collapses and small slabs were reported on Hale Bop on Saturday. These recent avalanches are a mix of small wind-loaded pockets and wet avalanches. 

  Today will be the warmest sunny day we've seen this spring, and we're expecting to see Loose Wet avalanche activity pick up as snow surfaces melt through the day. While the size of these avalanches is uncertain, it will be important to pay close attention to changing conditions on solar aspects. We will likely see roller balls and pinwheels starting to roll down sunny slopes midday, especially on slopes with rocks or trees, and below cornices. As surfaces continue to warm and weaken, we will likely see loose wet avalanches later in the afternoon. These will likely happen naturally, and can also be triggered by a person. Pay close attention to overhead terrain, especially sunny slopes in the afternoon.

  This problem can easily be managed by moving to shaded terrain as the solar aspects start to fall apart. If you are looking for dry snow later in the day, be aware that there are also buried weak layers lurking below the surface, which may be more likely on shaded aspects (more on this in Problem 2). 

   Cornice Fall: We may begin to see cornices failing naturally in the heat of the day. These can be large enough to be a hazard on their own, and they also have the potential to trigger larger avalanches as they tumble downslope. Limit spending time below large cornices, and give them plenty of space if you are traveling along ridgetops.

  There is a smaller chance of larger Wet Slab avalanches, especially on steep south-facing slopes with a thinner snowpack. These may fail at or near the ground, and the likelihood will increase through the day.

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  There are multiple layers of weak, faceted snow buried in the upper 2' of the snowpack. We saw a handful of natural and human-triggered avalanches fail on these weak layers during and immediately after last week's storms, and they remain a concern today. Most of the avalanches we've seen so far have been 1 to 2' deep, 50 to 100' wide, and have run anywhere from 50 to 500 vertical feet. These weak layers are becoming more stubborn as we move further out from the last loading event, but it is still an issue we are keeping on our radar.

  This type of problem gives misleading feedback, often showing mixed results in snowpit tests and sometimes showing zero warning signs even when conditions are dangerous. If you are getting into steep terrain, the best way to mitigate the risk of an avalanche like this is to take a close look at the snowpack in the area you are traveling in, and to avoid slopes with terrain traps like cliffs, rocks, trees, or gullies in the runout zone in case you get caught by surprise.

  Wind Slabs: The strong northwesterly winds that impacted the area yesterday have built a fresh round of wind slabs on top of a snowpack with weak layers near the surface. These will remain reactive today, and will most likely be found near ridgelines, below convex rolls, and in steep gullies.