Bollettino valanghe

East Cabinet Mountains

Idaho Panhandle Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Persistent weak layers consisting of rain crust and sugary snow are present in the upper snowpack across the mountains of the Kootenai. Avoid travelling in terrain steeper than 30 degrees at elevations above 5,000' where these widespread weak layers will likely be triggered by a rider. If you trigger an avalanche on one of these layers there will be high consequences.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    Across the area we have a combination of weak sugary snow (facets), resting on firm rain crust. The slab resting on top of this weak layer is about 20" thick or more. Test results show this layer to be consistenly failing and propagating with moderate force. What this means to you is that you may get away with riding in steep terrain without triggering an avalanche today, but I wouldn't risk it. This weak layer has a lot of potential and if triggered will likely propagate widely across a slope resulting in high volumes of debris and a deep burial. In the Purcell Range where the early March rain crust is thinner there is the potential for avalanches to step down below the rain crust, to an even deeper weak layer above 6,000' in elevation.

     

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2

    Light to moderate winds out of the southwest have transported snow onto leeward aspects at upper elevations. Be heads up for pockets of thick slabs near ridgelines above treeline. With our current widespread weak layers the potential to create a large avalanche may start with triggering a sensitive pocket of wind slab. Avoid riding below cornices in steep terrain this weekend and this problem will be easily avoided.

Avalanche Discussion

If I could slap my own definition on the current avalanche conditions I would say we are walking a line around a "moderate likelihood-high consequence" situation. Somewhat of a mental struggle for me to assign a hazard rating, this situation can also be a struggle for us humans to deal with when making decisions involving risk management. It is so much easier to make good decisions when the likelihood is clearly cut!

Here is what I am seeing this week. There are some issues in the snowpack that are very widespread in type and potential, but there is also some wide variance between the Cabinets and Purcells in the thickness of our early March crust layer. This difference in the crust strength and thickness has me somewhat worried about the potential for any avalanches that are triggered to step down to deeper weaknesses and create much bigger avalanches in the Purcells right now. In the Purcells yesterday the layer of concern was about 20" deep and propagating with moderate force. On Monday we were seeing failures on the facet layer with light force, this was prior to the storm that added another 10-12" to the upper slab. The upper snowpack will continue to become more resistant to triggers with time. A persistent weak layer is always a tricky problem to deal with and I would be patient and give it some time, spring will be here soon and the steeper terrain will still be there. 

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