Bulletin d’avalanche

Elkhorns

Wallowa Avalanche Center
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Danger d’avalanche

Fri
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

Winds out of the south combined with snow available for transport will create fresh slabs of snow up to 2' thick that will likely be triggered by a rider today near and above treeline on leeward slopes and cross-loaded mid-slope terrain features.  It remains possible to trigger a deeper slab avalanche up to 8' thick failing on one of several persistent weak layers deeper in the snowpack.  Avoid recently wind-loaded start zones, while keeping your slope angles less than 30 degrees to avoid the chances of triggering a large destructive avalanche that could fail on weak snow near the ground.  

This forecast is sponsored by The Wallowa County Gamblers Snowmobile Club.  

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Moderate to strong winds out of the South have been the highlight of the weather for the last few days.  These winds have formed sensitive wind slabs and cornices along leeward ridgelines and have also cross-loaded mid slope terrain features.  Look for clues of wind loading such as freshly formed snow drifts, cornices, and plumes of snow on ridgelines.  Wind slabs will feel stiff under your feet or machine and will likely crack under your weight.  Avoid obviously wind loaded start zones.  Below ridgelines, look for and avoid terrain features that are cross loaded- see photo for an example.  

    (1/11/2023) Photo: cm

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–3

    It remains possible to trigger a deeper and very large avalanche on weak snow that is buried 2-3' in the snowpack.  The Christmas Rain Crust is the likely culprit in this scenario and is more likely where you find the rain crust to be a crust/facet sandwhich where weak and uncohesive snow is layered between two harder crusts.  Spotty distribution of surface hoar buried 1-3 feet has also been reported throughout the northern and southern wallowa forecast zones and have shown reaction in snowpack tests and recently remotely triggered avalanches.  See recent observations here.  The lower likelihood, but higher consequence scenario is triggering a large slab avalanche either as a wind slab or slab avalanche failing on one of these layers, which could add enough weight to a slope and ultimately step down into weak sugar snow near the ground.  This is more likely in areas that hold a shallower snowpack- think areas in the upper elevations where wind has continually stripped snow, rocky areas that are mid slope, or lower elevations that have less than 4 feet of snow on the ground.  As you travel through the mountains today, it is recommended to track snowpack depths with your probe and feel for the depth and thickness of the Christmas rain crust.  If contemplating riding any slope steeper than 30 degrees, careful snowpack evaluation remains critical to look for this weak snowpack structure.  Play the long game- remain patient as our snowpack gains strength over time.  Check out the video below that shows our evaluation of this problem through several snowpack tests yesterday in the Northern Wallowas.  

Avalanche Discussion

The message stays the same as it has been for the last week.  Avoid wind loaded slopes near treeline and above treeline.  Avoid cross loaded mid slope terrain features, and keep your slope angles less than 30 degrees to decrease your chances of triggering a large to very large avalanche.  Over the last week, numerous human triggered avalanches have been triggered in the Southern Wallowas on wind loaded terrain features and in lower elevation areas that harbor spotty distribution of buried surface hoar.   It remains more likely to trigger a slab avalanche 1-3' thick where the Christmas rain crust is thinner and holds weak uncohesive snow around it.  While we haven't seen any avalanches running on the weak sugar snow near the ground since the avalanche in the Northern Wallowas on 12/30, snowpack tests and overall weak snowpack structure indicate that they are still possible.  We haven't had enough of a load in the form of snowfall amounts to overload the structure naturally.   We would still like to see another couple significant loading events (1"-2" of snow water equivelent) to naturally test the snowpack.  Don't let yourself or your riding partners be the additional weight that could tip the balance of this house of cards.  Stay the course- avoid consequential terrain above terrain traps, keep your eyes on your partners while only committing one person on a slope at a time, regroup out of runout zones from overhead or adjacent avalanche paths.  If uncertainty exists in your mind as to whether weak snowpack structure exists in the area you find yourself, use wide terrain margins and lower slope angles to hedge your bets.  

We have been receiving lots of great observations from around the forecast area lately.  Thank you!  It is extremely helpful to help us build these avalanche forecast products.  Keep them coming!  Submit an observation here.  

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