THIS AVALANCHE ADVISORY EXPIRED ON December 27, 2017 @ 5:49 pm
Avalanche Advisory published on December 26, 2017 @ 5:49 pm
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

The snowpack and its weak layers are gaining strength but still have the potential to fail and create large avalanches due to the thicknesses of this layer and the weak, sugary snow below it.  Keep in mind that most avalanche accidents occur on days when the hazard rating is considerable or moderate.

How to read the advisory

The snowpack and its weak layers are gaining strength but still have the potential to fail and create large avalanches due to the thicknesses of this layer and the weak, sugary snow below it.  Keep in mind that most avalanche accidents occur on days when the hazard rating is considerable or moderate.

3. Considerable

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Above Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

3. Considerable

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Near Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Persistent Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

The abundant snow that fell on December 18th-19th has created a cohesive slab 2-3' thick across the area.  This slab overlies multiple buried weak layersStability tests show that both this slab layer and buried weaknesses are  gaining strength; however, if triggered they will create very large avalanches with the potential to pull in snow from lower angle slopes that are adjacent should this slab move.

recent observations

Today we travelled into the Eastern Cabinets where we again heard multiple collapses on weak layers below 5,000'.   These sounds are a sure sign of instability and we noticed that they were most prevalant in terrain with a thinner snowpack and anchored terrain.  They also proved to be surprisingly stubborn in stability tests.  Conclusion-some very weak snow exists below 5,000'; however, it is unlikely to pose a threat in most areas due to vegetative anchoring.  Strong caution is advise at or below this elevation if you are in areas that are naturally open and void of vegetation.  As we travelled into higher terrain the snowpack thickened and stability tests showed that the snow that fell last weak has gained significant strength.  We had consistant results with failures occurring 32" below the surface, again failing on weak facets that are resting on the Thanksgiving rain crust.

 

Weather and CURRENT CONDITIONS
Disclaimer

Avalanche conditions change for better or worse continually. Backcountry travelers should be prepared to assess current conditions for themselves, plan their routes of travel accordingly, and never travel alone. Backcountry travelers can reduce their exposure to avalanche hazards by utilizing timbered trails and ridge routes and by avoiding open and exposed terrain with slope angles of 30 degrees or more. Backcountry travelers should carry the necessary avalanche rescue equipment such as a shovel, avalanche probe or probe ski poles, a rescue beacon and a well-equipped first aid kit.  For a recorded version of the Avalanche Advisory call (208)765-7323.