Avalanche forecast

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Avalanche problems likely exist on all aspects at all elevations today, complicated by bitter cold, so choose your terrain and routes wisely. Strong winds from all around the compass rose with lots of low-density snow available for transport over the past few days mean wind slabs will continue to be reactive today. All the snow from the past week will be loaded with 4”-6”of new denser snow today as temperatures increase—storm slabs are possible. 

Avalanche problems

  • Wind Slabs

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

    Weather data from Wardner Peak shows that wind came in from all directions at various times during this storm, with gusts exceeding 50mph coming out of the Northeast. With plenty of that Champaign powder available for transport, expect reactive 12”-18” wind slabs in unusual places.

    Wind slabs look like chalky pillows that will sound/feel stiff and hollow. Watch out for them on exposed ridgelines and cross loaded gullies at lower elevations. Low angle wind sheltered terrain will offer the safest skiing and riding.

    (12/21/2022)

    Fresh wind slab in the Silver Valley

  • Storm Slabs

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

    As the temperature modulates we can expect all the lite new snow from the past week to stiffen into a 1’ to 2.5’ slab, while 4” to 6” new denser snow will pile on top today. How this interacts with the previous snow surface and various density changes within the storm snow will determine its likelihood of propagating. We already have observations of a 2.5’ storm slab remote trigger avalanche on the old snow/new snow interface and natural releases in the past few days, so treat this with abundant respect.

    Mitigate this hazard by sticking to low angle slopes (<30°), and avoid traveling below avalanche terrain. Heed red flags like shooting cracks and whumpfs.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3

    You are probably sick of hearing us talk about this, but although it is becoming increasingly less likely to trigger this layer, if it were to go now might be the time. All the recent snow has added weight that is now bearing down on this layer buried 2/3 of the way down in the snowpack. If weakness persists in this layer and it is triggered from a shallow point in the snowpack, a convex rollover, or smaller avalanche steps down, the consequences of being taken for a ride would be dire with the potential for large to very large avalanches that run a long way. While increasingly unlikely, triggering one of the persistent weak layers would be very bad.

    The new snow, having buried this layer deeper, might be what puts this problem to bed for the season, but its too early to tell. Let things settle and assess its stability in coming days.

    (12/20/2022) Photo: J Thompson

Avalanche Discussion

Snowpack likes boring conditions. When weather changes drastically avalanche hazards spike. Today might be the best day to get outside between big weather shifts, but not enough time has elapsed to stabilize the snowpack from the recent storm events. The new snow today will likely be denser than snow from earlier in the week, setting up the possibility for an upside-down snowpack and increased instability.

The extreme cold will have preserved the soft powder, so it might be tempting to step out to slash some bigger lines, but there are multiple hazards at play today covering all aspects and all elevations. Sticking to <30° slopes is the safest bet. Heed red flags: recent avalanche activity, wind loading, cracking and whumpfs. Because of the potential to remotely trigger the storm slab from above, below or adjacent slopes, be very thoughtful about both your uphill and downhill travel routes: avoid traveling below steep slopes and above terrain traps.

Looking Ahead: The coming week will see multiple fronts moving through our area bringing warmer air and rain on snow events. It will be interesting to see how this plays out, but it will probably not be good.

Thank you to those of you who have submitted observations in the past few days, they are extremely helpful. Keep’em coming! Check out IPAC’s new observation platform: https://www.idahopanhandleavalanche.org/observations#/view

Be safe and happy holidays!

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