Avalanche forecast

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The snowpack has gone through significant changes recently, and multiple days of warm temperatures mixed with rain are creating wet avalanche problems.  It is possible to trigger a wet loose avalanche on all aspects, particularly in the trees where the snowpack is not as deep and fully saturated. Triggering a slab avalanche on weak layers will be a low probability, but high consequence possibility today. Assessing slopes for warning signs will be key before committing to steep terrain.

Avalanche problems

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1.5–3

    Weak layers in the lower portion of the snowpack exist and can been seen widespread at all elevations. Rain crusts from December are mixed between facets that were weakened from last week’s arctic cold front. Even though these layers are not consistently proving they can propagate and fail, the consequence of triggering an avalanche on any one of these weak layers would be very dangerous. The upper snowpack has taken on weight from rain and moisture and has the potential to overload a deeper weak layer if triggered. As you gain elevation to where temperatures have remained below freezing the wet slab problem will transition to the same persitant weak layer problems we have been talking about for weeks. The snowpack is "healing" and gaining strength at upper elevations where the temperatures are more moderate but have remained below freezing, but should be treated with caution until proven safe. Careful route planning and being mindful of what slopes you expose yourself to will be important for avoiding this low probability, and high consequence dangerous avalanche. 

  • Loose Wet

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

    Triggering an avalanche consisting of loose and wet snow will remain possible today. The snowpack has experienced a rapid warm up combined with a mix of rain and snow since 1/19. More rain than snow has been falling at tree line and below, and steep areas in the trees where the snowpack is shallow and saturated will be the easiest place to trigger a wet loose avalanche. Pinwheels gaining in size and gouging to ground have been reported, and this is a warning sign that the snow is losing cohesion. 

    Pinwheels forming from a steep road cut. This is a sign that the snow is moist and losing cohesion, and a precursor to wet loose avalanches 

Avalanche Discussion

We've seen a lot of change in the weather the past 2 weeks, and our snowpack is evolving quickly with it. The arctic front that came through 10 days ago caused the temperatures to plummet and created widespread and rapid faceting at the base of the snowpack and around rain crusts that developed throughout December. Now, we are experiencing unseasonably warm weather accompanied by rain and temperatures dancing just above freezing.

This rapid warm up has created wet avalanche problems that will persist until the snow has the ability to properly refreeze. Natural loose wet avalanches have been observed throughout the region on steep slopes, more commonly around rock bands where the snowpack is shallow and fully saturated. Observing pinwheels and rollerballs that fan out or gain size from your skis or snowmobile are indicators that this wet loose hazard exists. It is best to mitigate this problem by choosing to recreate on slopes that are less than 30 degrees, and do not expose you to overhead hazards. 

The sudden increase in temperature and moisture combined with the existing weak layers has also created the potential to trigger a wet slab avalanche. It is less likely to trigger a wet slab avalanche, but the consequences would likely be much more dangerous. A wet slab avalanche triggered on a weak layer that exists in the lower portion of the snowpack could result in a large avalanche consisting of very wet and heavy debris. If you consider venturing out to steep terrain, be mindful of what weak layers exist on the slope you intend to ski before committing to it, and stay aware of signs of pinwheels, tree bombs, and rollerballs.

A mix of snow and rain is expected for the next few days with temperatures hovering just around freezing. 

The completed report from the Steven's Peak accident that occurred on 1/11 is now published to IPACs website.

Accident report

 

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