Avalanche forecast

Central Cascades

Central Oregon Avalanche Center
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Avalanche danger

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

A major winter storm is exptected to bring an abundance of snow and we should be on the lookout for avalanches happening in the new storm layers and in wind drifted snow. Avalanches in wind drifted snow will be primiarily on the lee slopes near treeline and above on north, east, and south slopes while we should be on the lookout for avalanches in the new storm layers on any slopes where new snow has piled up 8" or more. Observe signs of unstable snow such as recent avalanches and cracking in the surface layers and if you have uncertainty in the stability of the snowpack, stick to slopes less than 30 degrees steep. 

Avalanche problems

  • Wind Slabs

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

    The wind will be increasing overnight and into Friday and will begin to move a lot of snow to lee slopes. The wind can pile up snow many times deeper than the snow that fell out of the sky and in doing so can make a denser slab overlying the softer snow below it. Wind slabs form in places where the terrain is conducive to accumulating blowing snow. Wind slabs are most sensitive to triggering when they are fresh and given the weather forecast I expect wind slabs to continue to build throughout the day. In some cases wind slabs will be building on old weak faceted snow and they may propagate faster and farther than usual, especially on north facing slopes, shaded slopes, and at high elevation areas.  

     

    ARCHIVE PHOTO

    Cracking in new wind slab as a skier approaches a convex roll. When you see cracking in wind slabs, that is a good indication of unstable snow.

  • Storm Slabs

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

    Storm slabs will build throughout the day as the snow stacks up and this problem will depend on how much snow actually falls out of the sky. When new snow begins stacking up to 8" or more, recognize storm slabs can begin to pack a punch if they are triggered. Use small test slopes and hand shear tests to check out how the storm slab is behaving. Storm slab avalanches will be more likely to trigger when heavier and denser snow is sitting on top of lighter weaker snow. 

    The old snow from before this storm had time to sit around and become faceted during the cold clear conditions leading up to the current snowfall. Triggering a storm slab on this faceted weak snow has the chance to propagate farther than normal. This can be especially true on north facing slopes, shaded slopes, and high elevation areas. 

    We may also see some small dry loose avalanches in steep terrain.

    ARCHIVE PHOTO

    Triggering a small storm slab on a test slope. 

Avalanche Discussion

The incoming snow will help us on our way to having good snow coverage in the mountains. We also need to keep in mind that avalanche danger typically ramps up with big storms, even in the early season. Going for a ride in an avalanche at this time of year can be particularly nasty due to the many exposed rocks, logs, and trees.  

We have a very shallow snowpack, but avalanches can still happen on slopes 30 degrees or steeper.  Remember even small avalanches can be dangerous in certain terrain such as steep slopes, constrictions where debris can pile up especially deep, and places where you can get dragged into rocks, trees, and over cliffs.

This is a great start to the season. Use terrain to your advantage and have fun out there!

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