Bollettino valanghe

Southern Wallowas

Wallowa Avalanche Center
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Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

New snowfall along with moderate to strong southwest winds have formed fresh, sensitive windslabs on leeward ridgelines and cross loaded terrain features that could be sensitive to a person or machine.  This new snow and wind blown snow has fallen on either the solstice rain crust or pockets of windblown snow that fell on last tuesday (12/22).  Although the chances may be becoming less likely, there is still the possibility to impact a deeper slab that could fail on weak sugary snow that is buried up to 2 feet in the snowpack.  You would not want to tango with an avalanche failing into this old weak snow.  

Problemi valanghivi

  • Wind Slabs

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

    Although snotel stations are only reporting 2" of new snow with .2" of SWE (Snow Water Equivelant), I would expect there are deeper snow totals in more favored locations.   The new snow, along with WSW winds in the moderate to strong category, have formed fresh sensitive windslabs along leeward ridgelines and cross loaded terrain features.  Observe localized wind loading patterns and avoid slopes that look like they have smooth and rounded surfaces.  Utilize small inconsequential test slopes to test the reactiveness of these windslabs.  Even a small windslab in the wrong location (think above terrain traps), could bury and/or injure a rider. 

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    The northern Wallowa mountains have a shallower snowpack than other zones in the WAC forecast area.  Generally speaking, a shallow snowpack in a cold environment facilitates a weaker snowpack.    A less likely but much more consequential avalanche problem that we are still dealing with is the interface of very weak, sugary snow that can be found 1-2 feet down in this forecast zone.   This interface was buried during the second weak of December.  Snowpack tests reveal that propagation is likely if this layer is impacted.  The Solstice Rain Crust (SRC) is helping to keep us from impacting this layer where it is thick enough to support the weight of a person and/or machine.  If you notice that you or your machine is breaking through the SRC and find yourself in snow above your knees, you are more likely to affect this weak layer.  If that is the case, best to avoid any slopes steeper than 30 degrees. 

    Recent observations from a northeast aspect of Chief Joseph Mountain reflected recent natural avalanche activity, although exact timing of the activity is unknown.  An extended column test also indicated that if impacted, this persistent weak layer consisting of faceted sugar snow (see below)  is likely to propogate, resulting in large avalanches.    Thanks for the great observation.  Keep 'em coming. 

    If unfamiliar with dealing with this type of avalanche problem, a rider should always default to choosing simpler, lower angle, less consequential terrain in which to ride or travel.  

    Recent Natural Avalanche Activity

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