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Northwest Avalanche Center
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In sintesi

Heavy snow and wind loading Friday night lead to peak danger Saturday morning. Wind drifts with enough snow to ride may trigger easily, on smooth slopes open slopes. Blowing snow and fresh cornices all point to the wind-loaded steep slopes to avoid.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
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    Probabilità
    Likely
    Dimensione
    1.5

    Dangerous avalanche conditions develop by Saturday morning in exposed upper-elevation terrain. Human-triggered avalanches (D 1.5) are likely and natural avalanches are possible. The culprit? Heavy snowfall that peaks Friday night into early Saturday along with a round of moderate to potentially strong winds SSW winds shifting westerly.  NWAC forecasters and rangers have not visited these elevations this year, so give yourself an extra margin for safety and avoid wind-loaded upper elevation slopes steeper than 35 degrees.

    You're most likely to recreate at middle elevations on Saturday given shallow lower elevation snow cover and stormy weather. More specifically, you're most likely to be tempted by the slopes that harbor the most danger on Saturday.  Wind loading will target slopes on the northern and eastern halfs of the compass. NW-N-NE aspects that retained coverage and a developed into a weak upper snowpack prior to the 11/30 storm cycle. While there wasn't enough of a slab on Friday to create avalanche danger, that will likely change on Saturday. Identify and steer around wind loaded start zones steeper than 35 degrees at these elevations, using trees and vegetation to access lower angle or less wind loaded terrain. If you find more than 6" of snow above the 11/30 crust, you can trigger an avalanche large enough to ruin your day.

    We think that lower elevation slopes still need more coverage before elevating avalanche danger levels. However, if there's enough snow to ride, there's enough snow to slide!

    Example: Blowing snow and wind loading (left) and scoured slopes (right), help you identify where slabs reside during a storm. 

    Photo: Sam Luthy Siemens

Avalanche Discussion

The Hurricane Ridge area only picked up 4-6" of snow thus far in the storm cycle. By Saturday, Hurricane Ridge lags a day behind the west slopes of the Washington Cascades where avalanche conditions became dangerous in many areas on Friday.

North aspects already have a shallow, but layered snowpack. You might find 6-12" of lower-density snow gradually forming a slab atop a crust-facet-crust combination. On N and NE aspects the upper crust is less than 1/2 inch thick, with a two inch layer of small facets above a stout crust. Avalanches could fail down to the stout crust with sufficient wind or snow loading, but this remains a low-likelihood scenario on Saturday. If you find evidence of shooting cracks or whumphs as you travel, this weak snowpack structure could be the culprit. The stout crust formed due to rain up to at least middle elevations before the late November dry spell. Shallow snowfall faceted during that late November drought that melted snow off of all but the NW-N-NE aspects.

As the new snow continues to stack up, remember that just a few days ago W-S-E aspects were bare ground. Dirt, rocks, downed trees, and stumps can catch you off guard while riding and may exacerbate a fall or any avalanche.

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