Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

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

Windy weather continues to maintain fresh pockets of drifted snow at mid and upper elevations. Watch out for pillow-like drifts near ridgelines, at the base of cliffs, and along mid-slope features. With the recent easterly winds, some of these slabs may hide in some unusual locations.

Problemi valanghivi

  • Wind Slabs

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

    Wind slabs, wind slabs, and more wind slabs… that seems to be the name of the game recently. Strong and gusty E-SE winds continue to build fresh wind-loaded pockets and add to older slabs. Given this wind direction, you may find wind-drifted snow in different locations than normal. So, make sure to pay attention and look for signs of wind-affected snow. Textured surfaces, sharp drifts, and blowing snow should help you anticipate local wind patterns and potentially loaded slopes. Steer around pillow-like drifts and seek our lower angled or less wind-affected snow to avoid this hazard. After several wind days, some of these slabs are growing larger, firmer, and harder to manage safely. Give large wind-loaded features a wide berth.

    (1/10/2023)

    Three natural wind slab avalanches from the past few days. Note the locations below cornices and along the base of cliffs. 

    Photo: Andy Harrington

Avalanche Discussion

Wednesday should be our last relatively quiet day before a major storm impacts the areas. While we aren’t expecting any new precipitation, strong E-SE winds should continue to transport snow. On Tuesday an NWAC forecaster in the Crystal Lakes and Morris Creek areas saw significant blowing snow and found several small loaded slopes that cracked and failed. He also spotted 5 natural wind slab avalanches from the past few days. Most of these occurred directly below cornices and along the base of cliffs (see photo above). 

Even though Tuesday should start with some sunshine, we don’t expect loose wet avalanches to be much of an issue. A new crust, cooling winds, and increasing clouds should limit any wet slide activity. Instead, you may just see a few piles of rollerballs. However, if you notice teardrop-shaped avalanches entraining snow, expect similar slides on steep sunny slopes. Don’t let one of these smaller avalanches push you into a creek or over a cliff. 

As we head into a more significant storm it’s worth taking stock of the snowpack. In sheltered areas, 2-3ft of snow now sits above the very prominent Christmas Crust. While in general, the upper snowpack is right-side-up and well-settled, it is not without potential weaknesses. 

  • 1/4 interface: This layer is often located about 10-15 in (25-40cm) below the surface. On Tuesday an NWAC forecaster found buried SH at this interface on NW and SE aspects in the Crystal backcountry. This layer has also been observed by NWAC staff and avalanche professionals at White Pass, Mt Rainier, and Mt Hood over the past week, While there are no known avalanches on this layer in this zone, it’s worth nothing going into the changing weather pattern.
  • Christmas Crust (12/27): This is a very stout and easy-to-identify crust at the base of the upper snowpack. In general, the bond between the snow and the crust has been strong. However, in a few occasions, weak snow has been seen on or just above this layer.

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