Elkhorns

Lawinenprobleme

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  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1–2.5

  Yesterday  I found myself in the Northern Elkhorns doing observations at low elevation locations. I dug a snowpit on a north northwest facing slope at 6655' . The snow at this location was about 4.5' deep, quite a bit shallower than what I have been finding higher up at treeline and near ridgelines. While traveling through the snow at this location I observed no signs of instability. I put in my snow pit and it became obvious that we have multiple persistent weak layers buried throughout the snowpack at this location. The Christmas rain crust is buried about half way down at this location and has thin, weak,  faceted layers above and below it. Compression tests performed in this snowpit revealed weakness at this layer. Columns failed using moderate force. The shears occurred in the faceted layer above the crust and were mostly smooth (CT18RP⬇️70cm). No propagation was observed on any stability tests I performed yesterday. WAC forecasters traveling in the Blues yesterday were seeing similar snowpack characteristics that I observed in the Elkhorns. Meanwhile, WAC forecasters in the Northern Wallowas, yesterday, observed buried surface hoar about 14" down from the snow surface at 6400' . Stability tests they performed at their location exhibited propagation and sudden planar shears (instability red flags) on that buried layer of surface hoar. That said, we are still concerned about what we have been seeing and what we have been hearing about throughout other areas of our forecast zone this past week. Myself and other WAC forecasters have been observing propagation in our snowpit stability tests. Also, in the Observations area of this website you will find an interesting post about a snowmobile triggered avalanche that occurred in the Southern Wallowas in the Little Eagle Creek area. This was a persistent slab avalanche that failed on a layer of buried surface hoar and was big enough to injure or kill a human. Luckily no one was injured in the accident. The best way to eliminate the risk of triggering a persistent slab avalanche is by staying off slopes steeper than 30 degrees, staying out from under slopes steeper than 30 degrees, and staying off slopes connected to slopes steeper than 30 degrees. Give the new snow plenty of time to stabilize after this recent storm. Until this problem goes away it is important for us recreationalists to remain patient and disciplined by maintaining conservative terrain choices even when instability appears unreactive.

  

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  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1–2

  While ski touring in the Northern Elkhorns yesterday and Friday I also noticed north, northwest, and west winds blowing 15-25 MPH with occasional higher gusts at and above treeline and at ridgelines. Also, it was snowing off and on while on my ski tours, especially Friday in the afternoon. Although I observed no windslab reactivity while on my ski tours, I think the potential exists today that human triggered  windslab avalanches are possible above treeline on steep, leeward terrain throughout our forecast area. Suspect the possibility of triggering a sensitive windslab on any steep slope at and above treeline, and at ridgelines today. Evaluate snow conditions and terrain carefully before you commit to that steep slope. 

  

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  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Unlikely

  Größe

  1–3

  We are still seeing poor snowpack structure in our snowpack in the form of basal facets and crust facet combinations near the ground in the Elkhorn mountains and in the Northern Wallowas. These deeply buried persistent grain types are still failing in snowpit stability tests, so the deep persistent problem is still on the table for the Elkhorn Mountains and Northern Wallowas. The likelihood of triggering one of these very dangerous avalanches is low but the consequences of doing so would be dire and involve most of the snowpack. A deep persistent avalanche can be triggered on steep terrain where the snowpack is thin and rocky. The best way to manage the risk is to stay off of and out from under slopes steeper than 30 degrees while this problem persists, especially near shallow rocky areas.