Bollettino valanghe

Blues

Wallowa Avalanche Center
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In sintesi

New snow from Thursday fell lightly on the raincrust that exists throughout our forecast area, up to 4" at some locations. The bond at this interface is tenuous resulting in loose dry avalanches (sluffs) on terrain steeper than 35 degrees. If you venture out onto these steeper slopes this weekend it is possible that you could see and even trigger a loose snow avalanche. Evaluate snow and terrain carefully before committing to that terrain.

Problemi valanghivi

  • Loose Dry

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

    Last Thursday we saw the first significant snowfall since the storm on January 12. Up to 4" of light new snow fell (in some locations)and is sitting atop the rain crust that remains from the January 12th event. Thursday's new snow has not had sufficient time to bond to that rain crust it sits upon. This condition exists on all aspects and elevations. When recreating on slopes steeper than 35 degrees expect to see loose dry avalanches or sluffs. On larger slopes these sluffs can entrain a large quantity of snow. Large sluffs have the capacity to knock a skier or snowboarder off his or her feet. If the skier or rider happens to be recreating in high consequence terrain and is caught in a large sluff, the sluff could carry that skier/rider into an undesirable situation, like over a cliff band or through steep gladed terrain. If you choose to recreate on steep terrain this weekend, have a sluff management strategy for any steep slope you plan to descend before you commit to that slope.

  • Loose Wet

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

    Today looks to be sunny throughout the mountains of Northeast Oregon. This sun can have a weakening effect on newly fallen snow. Loose wet avalanches or wet sluffs occur when the surface snow becomes warm and wet and loses strength. Wet sluffs can be more powerful than dry sluffs because they are denser and heavier. Avoid being on or under steep sun drenched slopes today that are showing signs of instability. These signs of instability include roller balls and the observance of sluffs.

Avalanche Discussion

Until Thursday there has been no measurable new snow since January 12. Where I was touring today in the Northern Elkhorns there was 4" of new snow (from Thursday) sitting on top of a semi supportable rain crust from January 12. I observed good stability except for loose dry avalanches (sluffs) on terrain steeper than 35 degrees. I also dug a snowpit on a 35 degree east facing slope at 8400' . My test columns failed using the maximum amount of force. No propagation or planar shears were observed. The ECT test revealed weakness just below the uppermost rain crust about 13 cm's down, no propagation. I performed a compression test as well which failed 130 cm's down in the basal facets. The fracture plane was irregular and the block was resistant to sliding. At this location the snow depth is 165cm's and the Solstice Rain Crust (SRC) is down 75 cm's from the surface. The SRC was unreactive in my snow pit tests. That said it is still a weak layer in the snowpack that we are concerned about, especially in areas where the snow depth is thin. Underneath the SRC all the way to the ground are the November facets. This layer is consolidating and gaining strength. For more detailed information about the Blue Mountains,check out the recent observation posted by Mike Hatch on January 20th. Also check out the observation posted on January 22nd.

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