Bollettino valanghe

Blues

Wallowa Avalanche Center
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Pericolo valanghe

Fri
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
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In sintesi

Strong winds and new snow will overload a weak snowpack.  Dangerous avalanche conditions exist with human-triggered avalanches very likely and natural avalanches likely.  Today is a great day to stick to low-angle terrain avoid traveling under all steep slopes and avoid runout zones.  

This forecast is sponsored by the Wallowa County Gamblers Snowmobile Club in Enterprise, OR.  

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1–2

    Read this observation from a local rider if you are questioning the likelihood of triggering a wind slab.

    The combination of snowfall and wind over the past few days has created dangerous avalanche conditions.  Touchy wind slabs will likely be found on all aspects at both middle and upper elevations.  Look for signs of wind-drifted snow, dune-like formations, fresh cornices, and ripples in the snow surface.  Look for wind slabs near ridgelines as well as mid-slope terrain features. 

    With all the new snow and wind expect to trigger slabs 1-3 ft thick.  As you move up in elevation be aware that the potential for an avalanche and the size of the avalanche will increase.  These newly developed wind slabs are sitting on top of a weak snowpack structure which can result in the avalanches breaking easily and perhaps much larger than you would expect.  This situation has the potential to affect layers deeper in the snowpack and trigger a persistent slab avalanche.  

    Watch for changes in the snow surface.  If it becomes stiffer, is rippled, or makes a drum-like sound then you are traveling on a wind slab.  Watch for shooting cracks as you travel through the terrain.  

    With this combination, it is recommended to stay out of avalanche terrain.   There have been two reports of wind slabs triggered in the past few days, large enough to bury and kill a person.  

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–3

    The snowpack does not like sudden change.  With a weak structure in the snowpack and a new load of snow pressing down on it, persistent slabs are likely to release today.  For the past couple of weeks, we have been talking about the poor snowpack structure and the numerous crusts and facets that we have in the snowpack.  Now we are going to see why we kept talking about all those crusts and weak snow.  The new snow is adding weight to the poor structure and will see avalanches between 2-4 feet or even to the ground.  Snowpack collapsing and whumpfing noises are clear signs the snowpack is unstable. 

     

Avalanche Discussion

This is the first major loading event we have had this year on our weak snowpack.  Since January 6th we have seen between 1-7" inches of water and between 12-30+ inches of snow in our different zones.  Winter has arrived in full force.  As mentioned above for the past few weeks, our snowpack structure is weak with many crusts and weak snow within the snowpack.  With this new snow and winds, we will be testing the strength.  

The snowpack in the Blues does now have as weak of a structure as we are seeing in other zones, however, they have been getting the majority of the snow over the past few days.   With close to 3 ft in a short period, avalanches are likely.  The Northern Wallowas have not received as much snow recently but they have a weak snowpack structure.  Be very careful when moving through the terrain as the newly developed wind drifted snow could awaken the weak layer at the bottom of the snowpack and avalanches could run further and deeper than you would expect.  The Southern Wallowas have also received the majority of the new snow with close to 3 ft in the past few days.  

A local rider triggered a wind slab in the Elkhorns on Monday that was large enough to bury a person.  This avalanche was around 7300 ft on a north aspect and the crown of the avalanche was 50+ cm deep and was about 60-70 meters wide.  It was reported that it failed on one of the many crusts we have in our snowpack.  This individual also reported that they encountered wind slabs behind features such as rocks, ribs, and trees throughout the slope.   

It's not over yet.  Today through this weekend we will continue to see an active winter weather pattern move through the area.  Snowfall is expected to ramp up today with between 9-16" in the forecast today with strong to extreme winds.  

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