Avalanche forecast

East Cabinet Mountains

Idaho Panhandle Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Weak layers are present in the upper two feet of the snowpack in the form of rain crusts and buried surface hoar.  It is possible to trigger avalanches in leeward terrain near ridgelines where wind deposited snow is forming cohesive slabs on north and easterly aspects.  Build some margin for safety when approaching slopes greater than 35 degrees at middle and upper elevations.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Buried surface hoar remains present in many locations on north and easterly aspects.  It may be buried over two feet deep in places and while stubborn to trigger this layer is still unpredictable.  Additionally about a foot of snow is sitting on a weak snow interface around the 1/13 rain crust.   In wind loaded locations this "new" snow is forming a cohesive slab and becoming more sensitve to triggering.  Approach convex and rocky terrain with skepticism.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Winds speeds have been strong enough to entrain available snow and form cohesive slabs near ridgelines and gullys.   The windslab problem is amplified where it rests on or above persistent weak layers.  Expect thicker and more reactive slabs the higher you climb. 

Avalanche Discussion

Incremental accumulations of snow and rain this past week have added weight and increased the complexity of the upper snowpack.  We were pleased to find about 13 inches of snow on a supportive rain crust formed last weekend (1/13).  Unfortunately the new snow was not well bonded to the crust and a thin freezing rain crust deposited Tuesday night was evident 3-4 inches below the surface.  In sheltered areas snow was not consolidated enough to form a cohesive slab, but where it  is loaded by the wind, slab formation was evident.  The other thing that was evident was the weak interface between the rain crust and snow above.  With more snow forecasted Saturday night, this interface is worth keeping in mind moving into Sunday.  Digging deeper, a layer of buried surface hoar is still intact about two feet down.  It is currently bridged by the 1/13 rain crust and producing inconsistent results in stability tests, with moderate to hard force failures.  An avalanche triggered on this layer would be a high consequence scenario. 

Winds that were strong enough to transport snow and form small slabs accompanied each shot of moisture this past week.  Windslabs are present near ridgelines and gullys at mid elevations and above, but are deepeer and more sensitive the higher you climb.  Sitting above the persistent weaknesses, these windslabs have potential to be larger than expected so conservative terrain management and travel practices may be warranted to manage this problem.  Don't let your guard down as this persistent slab problem evolves. 

 

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