Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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In sintesi

Keep an eye out for wind affected snow in exposed, downwind terrain closer to the Cascade Crest. If you see signs of instability such as cracking, collapsing, and recent slab avalanches, stick to more sheltered terrain.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1

    Little snow inputs from Friday into Saturday night with strong-extreme ridgeline wind speeds keep wind slabs on the table for areas close to the Cascade Crest. Although small, these slabs may have trouble bonding to slick crusts, surface hoar, and faceted snow below. Anticipate wind-affected snow lower down on slopes than you might expect. It is unlikely, but you could trigger a bigger and more consequential avalanche at upper elevations where older, deeper wind slabs are overloaded by fresh slab formation and fail on weak layers below.

    Blowing snow will tell you where slopes are being freshly loaded. Cornices and hard, uneven snow surfaces will point you toward where wind-affected snow - new and old - can also be found. These areas are commonly just below ridgelines and in cross-loaded gullies. Shooting cracks, collapsing, and recent slab avalanches are clear signs that you should avoid steep, exposed terrain.

    A small crown in wind drifted snow on Axis Peak on Wednesday. This is the type of terrain you may find lingering slabs in. 

    Photo: Katie Warren

Avalanche Discussion

Friday's storm underperformed and Saturday night's storm totals sure aren't anything to be chomping at the powder bit over. What keeps the wind slab problem on the list is primarily two other important factors.

  1. We expect to see some impressive ridgeline wind speeds Friday night into Saturday morning. The wind will decrease throughout the day on Saturday, but will still be strong enough that any snow available for transport will move around.
  2. The snow will be falling on a variety of weak and slick surfaces: 
    • Observers continue to find buried surface hoar in the upper snowpack that responds inconsistently in snowpit tests. It may only take the weight of a new small slab to initiate failure at this layer in areas that were previously wind-loaded. If you decide to commit to a steeper slope, it'll behoove you to dig a quick hand pit to see what layers are underneath first.
    • After warm temperatures and rain up to 5000 ft on Friday, we expect there to be firm crusts below new snow. These areas will be more widespread at middle elevations and will create some hazardous travel under softer snow surfaces. Remember, a small avalanche that knocks you off your feet or machine could carry you into hazards such as cliffs and trees.

If you've ever found yourself wondering which direction you should look for wind loading if you encounter rippled, uneven snow surfaces, the best way I have found to think about it is that the "pointed" ridges of the ripples "point" towards the prevailing wind direction. It is a similar concept to how riming on trees usually happens on the side of the tree facing the wind.

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