Avalanche forecast

Central Cascades

Central Oregon Avalanche Center
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Avalanche danger

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

The considerable avalanche danger that we have had on Sunday and Monday will increase due to prolonged periods of heavy snowfall on Tuesday.  Avalanches near and above treeline could be very large in wind deposited snow or if they involve persistent weak layers deeper in the snowpack.  Stick to smaller slopes below treeline, or avoid skiing slopes steeper than 30 degrees altogether.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–2.5

    We have received around 45 cm. snow over the weekend and wind slabs associated with that storm may be only beginning to stabilize.  Some of these may overlay weak surface snow from last week.  On Tuesday we will see heavy snowfall and extreme wind from the West and Southwest.  This could build new wind slabs.  Extreme winds often mean that wind hardened snow comes to rest further down slope and even in sheltered glades well below treeline.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3

    Before last weekend's snow, we were finding several persistent weak layers in the snowpack.  These were burried surface hoar, and poorly developed facets near crusts.  The specific type and depth of these layers varies considerably by elevation.  Persistent weak layers were most common on north and east slopes near treeline and on sheltered alpine slopes.  They are also most common in the 30-40 cm. of snow beneath last weekend's storm snow.  As more snow loads above these weak layers, and there is the possibility of a smaller avalanche stepping down to deeper layers, very large avalanches are possible.  Travel on north and east slopes near treeline and above is not recommended on Tuesday.

  • Storm Slabs

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

    Prolonged periods of heavy snowfall mean that storm slab avalanches are likely below treeline.  Avoid steep convex slopes, or slopes where terrain traps exist.  Hand shears, and test slopes are good ways to tell if you are dealing with a storm slab or loose dry avalanche problem.  Often with decreasing temperatures we can avoid a storm slab problem, but storm slabs are likely on Tuesday due to the very heavy rate of snowfall.

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