Avalanche forecast

Northern Wallowas

Wallowa Avalanche Center
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Avalanche danger

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

A series of potent winter storms will impact our forecast area today through Monday bringing significant snowfall and strong SW winds to our area mountains. The southwest flow is perfect for unleashing copious amounts of precipitation on the Southern Wallowas. We can expect 18 - 24" of new snow in the next 24 hours. Sunday into Monday the zone could pick up another 12 - 18" of new snow. The existing snowpack exhibits weak strength and poor structure and the weight of the new snow will stress the snowpack to its breaking point. Expect reactive storm slab instability to increase throughout the day at all elevation bands and stout unstable wind slabs ( 12 - 24" thick) to form at upper elevations near ridgelines on N-E aspects. Natural avalanches are possible and human-triggered avalanches are likely on slopes greater than 30 degrees. The avalanche danger will increase throughout the day and into early next week. 

Avalanche problems

  • Storm Slabs

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

    In the Southern Wallowas we can expect 18 - 24" of new snow in the next 24 hours and up to 3' of new snow in some locations by Monday evening. The existing snowpack exhibits weak strength and poor structure and the weight of the new snow will stress the snowpack to its breaking point. Expect reactive storm slab instability to increase throughout the day at all elevation bands. Natural avalanches are possible and human-triggered avalanches are likely on slopes greater than 30 degrees. The avalanche danger will increase throughout the day and into early next week. A particularly troubling possibility is a skier or rider could trigger a storm slab avalanche and the weight of the slab could "step down" and initiate a failure deeper in the snowpack in a persistent weak layer. The resulting avalanche could be catastrophic. The best way to stay safe in the backcountry the next few days is to avoid avalanche terrain all together. Stay off and out from under slopes greater than 30 degrees. 

  • Wind Slabs

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

    The Southern Wallowas can expect 18 - 24" of new snow in the next 24 hours. The existing snowpack exhibits weak strength and poor structure and the weight of the new snow will stress the snowpack to its breaking point. Strong SW winds throughout the day (10-20mph, gusting upper 20's) will form stout unstable wind slabs (12 - 24" thick) at upper elevations near ridgelines on N-E aspects. Pockets of reactive wind slab will also develop mid-slope on cross-loaded terrain features like ribs and gullies. Natural avalanches are possible and human-triggered avalanches are likely on slopes greater than 30 degrees. Avoid wind-loaded and cross-loaded terrain features greater than 30 degrees. Keep an eye out for shooting cracks, collapsing of the snowpack (whoompf sound), and smooth pillows of hard snow; these are signs of unstable wind slabs. Expect the avalanche danger to increase throughout the day and into early next week. 

Avalanche Discussion

Here it is folks! Happy New Year as we welcome the La Nina weather pattern to the Northwest. A strong jet stream and deep moisture plume in the Pacific Ocean will feed potent storms into our area for the next week. Under southwest flow and due to the NW-SE orientation of the mountains, the Southern Wallowas will pick up the most snow in our forecast area. While we welcome the copious amounts of new snow that will fall throughout our area mountains the weight of the new snow will stress our fragile existing snowpack to the breaking point. The fact is our exising snowpack is weak and chock full of persistent weak layers. The weight of the new snow combined with the weight of a skier or sled will likely be the straw that breaks the camel's back. In most locations the bottom two feet of the snowpack is composed of weak faceted grains (sugar snow) and then we have a scary crust/facet combo about 18" to 24" down from the surface that has been reactive in our snowpack tests even without the additional stress of new snow. In short...this is the perfect recipe for an avalanche sandwich. To make matters worse, the weight of a storm slab avalanche triggered by a rider could be enough stress to "step down" and propagate an even larger avalanche from deeper down in the snowpack at one of our persistent weak layers. The result would be a large and catastrophic avalanche. The best bet to stay safe the next few days is to avoid avalanche terrain all together - stay off and out from under any slopes greater than 30 degrees. 

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