Avalanche forecast

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
1 · Low
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Highlights

Although the snowpack has settled and strengthened since last week’s storm, persistent weak layers remain buried in the snowpack. Anticipate avalanche danger to rise to Considerable today as more snow and southerly winds build slabs on northerly aspects.

Avalanche problems

  • Persistent Slabs

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

    Last week’s snow has coalesced into a an increasingly stubborn slab resting on layers of weak sugary facets and a crust. This is a mixed bag. The slab has strengthened and is showing mixed reactivity in stability tests: it appears to be beginning to bridge buried instabilities in some areas, while remaining reactive in others. The bad news is that if it were to break free it would be a stiff 1’ to 3’ slab of significant consequence. This problem is widely distributed on all aspects at upper and mid-elevations, but reactivity is difficult to predict. If this were to go it would most likely initiate on steep unanchored slopes (>35°). Factor in a wide margin of error in your decisions today.

  • Wind Slabs

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

    Today’s snow is coming in with southerly winds.  Wind slabs will continue to build today with additional snow and southerly winds causing avalanche danger to rise at treeline and above on northerly aspects. You can manage this hazard by avoiding cross-loaded terrain, convex rollovers and loaded pockets below ridgeline.

Avalanche Discussion

The generally mild weather in the 20’s and low 30’s over the past week has given the snowpack time to settle and begin to “heal”, meaning we are trending toward greater stability. However, depth hoar, basal facets and a layer of surface hoar are all still buried in the snowpack. While triggering these is becoming less likely, avalanche professionals in the area agree these weak layers are still widespread and their reactivity is difficult to predict.

Use good terrain choices today to manage avalanche hazards: Ski and ride in anchored terrain. Watch for areas with shallow(er) snowpack (around rocks, etc.) that might be more reactive than surrounding areas. And watch out for wind slabs, especially on northern aspect ridges. Our snowpack remains shallow and therefore potentially reactive throughout its entire depth. Much of our terrain is well anchored by small trees, logs and rocks that are still poking through the shallow snowpack. However, areas with smooth slopes >30°, like big bear grass meadows or bedrock, are more likely to slide on the weak base layer of sugary facets. Heed red flags: whumpfs, shooting cracks and sudden collapses in the snow.

Call to action: Avalanche professionals rely on weather reports, snotel sites and field days to gather the data needed to build a forecast. But effective avalanche forecasting is a community effort: PLEASE SUBMIT OBSERVATIONS. Don’t be intimidated, you don’t have to be a professional to make observations. Basic information such as: location, snow depth, whumpfs, shooting cracks, wind effected snow, and incidents of natural or human triggered avalanches are all helpful in building a more complete picture of what is happening across the forecast area. Help us help you. Thanks

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