Bollettino valanghe

Central Cascades

Central Oregon Avalanche Center
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Pericolo valanghe

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

In sintesi

Avalanches will be possible at our highest elevations, where it hasn't rained and the snow remains dry.  Dangerous Wind Slab conditions could exist on North and East slopes that the wind has blown snow onto.  On Thursday, there was a report of one such Wind Slab stepping down to the December 7 rain crust and producing a very large avalanche.

Problemi valanghivi

  • Wind Slabs

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

    Our mountain tops appear to be high enough that they avoided the wetter precipitation that fell on Tuesday afternoon.  Wind slabs that were built during the last storm will linger, and the wind can continue to move snow at these elevations.  Sustained winds from the Southwest will have loaded North and East slopes.  Some of these Wind Slabs could be quite hard or deep, so doing some assessment more than just a ski cut is prudent before committing to steep or consequential lee slopes.

    We've had a report of a Wind Slab stepping down to the 12/7 rain crust, which is over a meter deep in places.   The size of the resulting avalanche should be giving us all a bit more hesitancy than we typically might have under Moderate hazard with a Wind Slab problem.

  • Deep Persistent Slabs

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

    On Thursday, there was a report of a Wind Slab that stepped down to the December 7 crust.  In many places near treeline I've been finding this crust around a meter down, but on wind loaded slopes it is deeper.  In this case the resulting avalanche was size 3.  Our observers and forecasters have been keeping an eye out for possible weak snow around this crust.  I haven't found any evidence of well developed facets, and in most cases the "weak layer" isn't weak enough to produce avalanches.  However, with enough load, and a big enough trigger (in this case a big Wind Slab avalanche), it can fail.

    Whenever we have a Deep Slab, we have an increased amount of uncertainty to deal with.  It can be difficult to assess the weak layer.  Although in this case we have been watching it continuously.  My riding strategy will be to avoid those scenarios that could produce the big trigger:  I will be more conservative in my decision-making on large, lee slopes, and steer clear of cornices.

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