Avalanche forecast

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Highlights

Mild weather with minimal precipitation in the last 24 means that our avalanche danger is moderating. Although isolated and unlikely, persistent weak layers exist in our snowpack and if triggered could be large enough bury a person. Also, spring like weather means that wet avalanche problems are in the forecast. Plan your tours with enough time to perform stability tests on slopes you intend to ride and avoid solar aspects in the afternoon.

Avalanche problems

  • Persistent Slabs

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

    The early March “atmospheric river”, followed by a cold snap, then spring warmth and waves of precipitation have created an upper snowpack that has grown in complexity. There are at least two layers of concern to us right now: The first is a layer of weak faceted snow just below a crust 50-70 cm from surface that I found on all upper elevation aspects yesterday. This layer was showing signs of reactivity, although stubborn, in stability tests. The other layer of concern is near surface facets buried 1 to 2 feet down that sit on top of the robust early March crust. It appears this layer has been preserved in isolated locations; however, coming up with generalizations about the locations where this layer can be readily found in our forecast zone (and therefore avoided) has been difficult, as rain and moderate temperatures have erased it in many locations.

    The take home message for these layers is that there is a fair amount of uncertainty about their reactivity and spatial distribution, yet an avalanche triggered on either of these layers, including those that step down from smaller slides, can break wide and deep and has the potential to bury a person. Under these circumstances it is important that riders assess stability themselves before stepping out into high consequence terrain. As always, the easy answer is to ride low angle slopes (<30°), stick to ridges and avoid terrain traps.

  • Loose Wet

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

    Overnight lows last night were just below freezing. With afternoon temperatures predicted to reach into the mid 40’s today and tomorrow, wet avalanches are a concern. Liquid water from melting surface snow on will lubricate the snowpack below, which could trigger otherwise latent instabilities. If the sun is out, plan your tours to avoid south and west aspects in the afternoon when tree bombs, roller balls and small point releases will be signs that instability is increasing. Loose wet slides can sweep a rider off their feet into terrain traps such as cliffs and trees, or bury a rider in a gully or runout.

Avalanche Discussion

In the past week we’ve gotten anywhere from 4 inches to a foot of new snow in the mountains, that has ranged in consistency from Slurpee at low elevations to blower powder at our highest elevations. The peak of avalanche hazard from earlier in the week has moderated with mild temperatures and tapering off precipitation. There are soft slabs in the upper 9 inches of the snowpack formed at various storm interfaces. These are not overly concerning, but the buried persistent weak layers are. Although the likelihood of triggering a slide on one of the persistent weak layers appears low, the threat of a consequential avalanche should persuade you to proceed with caution. Our confidence on being able to pinpoint where these layers remain present and reactive is low. Perform stability tests on slopes greater than 30 degrees before you decide to commit.

The Spring freeze melt cycle might be here to stay. Start to plan your routes accordingly: if the clouds part, plan to be off south aspect slopes by early afternoon when the solar warming will increase the likelihood of wet avalanche problems.

Between these two problems, the easiest terrain choices with good riding will be relatively low angle, sheltered, north aspect slopes where you are likely to still find fun, soft snow. Enjoy it while it lasts!

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