Avalanche forecast

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Avalanche danger

Wed
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

Rain on recent snow and a dry upper snowpack means that wet slabs are the primary avalanche problem today. Natural wet slab avalanches are likely and human triggered avalanches are very likely. Rain continuing today and intensifying again tonight will continue to drive this instability. Wet slab avalanches are notoriously tricky to forecast, and we always have a high degree of uncertainty regarding when avalanches might occur and how large they might be in conditions like this. We do know that the key ingredients for truly large and destructive wet slab avalanches are in place today. Avoid avalanche terrain, meaning both steep slopes and the flatter runout zones below them, if you choose to venture into the backcountry today.

Avalanche problems

  • Wet Slabs

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

    Wet slab avalanches will remain likely to release naturally and very likely to be human triggered today. Snowfall totaling 8-12” turned to rain yesterday afternoon and is forecast to continue through today and tonight. This water is affecting our previously dry upper snowpack by percolating down and decreasing strength of weak layers. Avalanches could fail on a particularly deep layer and be very large. We also might see many smaller wet slab or wet loose avalanches. Flat and low angle areas that aren’t in the runout of steeper slopes are the only places you can truly avoid this avalanche problem.

    (2/28/2022)

    A few roller balls, afternoon of 2/28/22: Early signs of rain wetting the storm snow.

    Photo: Ryan Matz

Avalanche Discussion

Heavy snowfall yesterday turned to rain late afternoon, for essentially our entire St. Regis and Silver Valley zone, as snow levels rose to 7,000’. Since then, about ½” of rain has fallen, with up to another ½” forecast today and possibly ¾” tonight. Prior to the rain, storm slab avalanches up to 12” thick were easy to trigger. This new snow is on a variety of surfaces, primarily old wind slabs and storm snow from last week. Below that is a crust formed around Valentine’s Day which sits a few inches or more above our January 12th crust. Weak, faceted snow has been observed around both crusts and our old, spatially variable surface hoar layer is somewhere between them where it’s present. The water that’s being introduced to the snowpack could weaken any of these layers.

As forecasters, we’re always uncertain about potential size and especially the timing of peak instability when conditions line up for wet slab avalanches. We do know that our current conditions of significant rain on a generally dry snowpack with existing weak layers is when large wet slab avalanches tend to occur. Temperatures may not drop significantly until Thursday, when refreezing might allow this wet slab problem to stabilize. Until then, the high risk for minimal reward of a soggy experience in the mountains should keep most of us out of avalanche terrain.

IPAC still has spots open Wilderness First Aid for Winter Backcountry Users and Avalanche Level 2 classes. These are great opportunities to improve your skills with knowledgeable local instructors. Check them out here!

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