Bollettino valanghe

Central Cascades

Central Oregon Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Human triggered avalanches in wind deposted snow were observed on Thursday and will be possible to trigger again on Friday near and above treeline on lee slopes.  Use careful evaluation to determine where wind deposits have accumulated, and look for signs of unstable snow such as cracking and previous avalanches. Identifying wind loaded slopes is key and you can always choose terrain less than 30 degrees steep to increase your safety margin. 

Problemi valanghivi

  • Wind Slabs

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

    Skier triggered wind slab avalanches were observed on Thursday on north facing terrain near treeline; reported size D2 (large). Size D2 avalanches are large enough to bury, injure, or kill a person. No injuries were reported. No natural avalanches were reported. Wind slabs were observed to be most prominent on north facing slopes, but keep in mind shifting winds can load periphery slopes. In addition, winds wrapping around features can create cross slope loading. 

    Snowfall is expected to be minimal on Friday, but there is still snow on the ground available for transport and wind slabs will still be forming in the terrain. It will be important to identify slopes that have been wind loaded. Use safer and lower angle slopes, to identify where wind loading has occured and to look for signs of unstable snow such as cracking in the slab. Wind slabs tend to stabalize after a few days but it can take longer where the slab is sitting on lighter and weaker snow. 

    Look for wind slabs below ridge tops, peaks, and other features that catch blowing snow.

    Keep in mind there can be a lot of variablity in the mountains. Wind loading can be more or less with just a few degrees difference in aspect. If you have any doubt about the snowpack, stick to slopes less than 30 degrees steep. 

    (1/12/2023)

    Skier triggered wind slab avalanche on a north aspect near treeline. Reported size D2 (large)

    Photo: Jonas Tarlen (COAC observer)

  • Cornices

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Cornices were building throughout the day as the southerly wind moved snow over ridge tops above north facing slopes. Cornices can form in conjunction with wind slabs, as they are both a product of wind transported snow. Be cautious approaching ridge tops when you do not have a good vantage point to determine if cornices are present or how big they are. Cornices hang over a slope like a diving board and can break off under the weight of a person. Cornice breaks can also result in large chunks of snow tumbling down the slope below.

    (1/12/2023)

    Recent cornice growth at ridge top above north facing terrain near treeline. Cornices have most likely formed at ridge tops above treeline.

    Photo: Jonas Tarlen (COAC observer)

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    This problem is specific to the lower elevations in the forecast zone (such as Santiam pass) where temperatures will remain in the upper 30's to low 40's with some rain possible. Monitor how deep slushy wet snow is. As slushy snow becomes boot top or deeper, avalanches could become larger. Look for rollerballs and pinwheels as precursors to wet loose avalanches.

    Wet slab avalanches could also be possible as melt water makes its way into snow layer interfaces in the upper snowpack. 

Regioni coperte