Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avalanche danger will increase as we receive more snow. Your largest concerns exist in wind deposited areas on upper elevation northerly aspects. Feel for thicker snow deposits, pay attention to cracking or whumphing, and avoid steep slopes where you encounter these conditions.

Avalanche problems

  • Wind Slabs

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

    Backcountry users triggered 4-6 inch wind slabs in recent days, and expect to encounter more as we receive additional snow. Temperatures will increase throughout the day, which could mean heavier, thicker snow surfaces that would fail easier on lighter underlying snow. Or, it may make the slabs more stubborn and not as reactive. Investigate for these qualities as you travel. 

    Feel for changes in snow hardness as you travel. Plunge your poles into the snow to check snow depths and feel for stiffer slabs if you use poles. Search for drifting on convex rolls, near rocky outcroppings, and in gullies. Pay attention to long shooting cracks if they occur. If you find any of these characteristics, stick to lower angle terrain and avoid nearby steep slopes.

    (2/1/2022)

    Several shallow wind slab avalanches occurred in recent days. 

    Photo: Pete Durr- USFS Backcountry Ranger

  • Persistent Slabs

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

    Remotely triggered avalanches occurred in recent days in neighboring zones.  Two in the West North zone were on steep, northerly upper elevation terrain in conditions similar to what we're experiencing here.  We suspect both of these failed on a persistent weak layer near the late January crust, buried around a foot deep. They were both in wind-loaded locations, and both failed in isolated pockets, indicating the cover of the persistent weak layer could be inconsistent. It’s tough to know where the layer could be on a slope-wide scale. You might find it in one spot, but not just adjacent to it. 

    Frequent investigations down to the layer of concern are not difficult, as it is buried only 1-2 feet deep right now, although that may not paint a clear picture as to where you’ll find it on a slope scale if you’re moving quickly. Whumphs are very clear signs that a weak layer is present and collapsing. If it were steep enough, the slope could avalanche. Be wary around large, unsupported rolls on shady slopes. Consider avoiding them at northerly upper elevations right now, as it is uncertain how widespread this problem is.

    (2/1/2022)

    A small isolated pocket was remotely triggered by a snowmobile in the West North zone at 5500 feet on a northerly aspect. A persistent weak layer above the late January crust was likely the culprit.

    Photo: Mike Trowbridge

Avalanche Discussion

Around 6 inches of snow will fall Wednesday night, adding to the foot of snow we’ve received since Saturday. The crust layer is getting buried deeper, and more weight added to our weak layer of concern could mean it will become more reactive. If you’re planning on traveling in areas of the West Central zone close to the border of another zone, take a look at the neighboring forecast as well, as you may find conditions similar to the adjacent forecast. If you encounter any whumphing or avalanches we’d love to hear about it. You can submit an observation HERE. 

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