Bollettino valanghe

Olympics

Northwest 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

The most dangerous areas likely have the best riding conditions in sheltered wind-loaded areas to the lee side of ridgelines. If you find 6" or more of snow above the uppermost crust, steer around wind-loaded slopes steeper than 35 degrees.

Problemi valanghivi

  • Wind Slabs

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

    SW winds have loaded NW-N-NW-E-SE aspects. The recent snow has stripped snow off of most windward aspects, leaving only a few inches of snow. However, sheltered wind-loaded areas have 12-16" of snow. This snow has been battered and compacted by the wind, making it into a subtle slab that could release on top of a crust. You're most likely to trigger a wind slab (up to size 1.5) on a steep slope or convex, unsupported rollover in the terrain. As you move into areas with 6" or more of snow on top of the crust, dial back your slope angle and take the time to evaluate the surface snow for slab-like properties such as firm or punchy layers and cracking snow surfaces.

    Example: A small shooting crack in a wind-loaded pocket near treeline. These are the types of pillow-like drifts than can produce wind slab avalanches. 

    Photo: Shane Robinson

Avalanche Discussion

NWAC and NPS Professionals confirmed that winter conditions have indeed returned to Hurricane Ridge.  The Ridge picked up 3-4" of snow on Thursday, which sits atop a melt-freeze crust on sun-exposed aspects, but likely not on shaded slopes. Below the 3/17 interface, 7-8" of snow fell Tuesday. Both the snowfall Tuesday and Thursday has been redistributed preferentially onto N-E aspects. The stout early march crust is present on all aspects and may have discontinuous pockets of facets just above it. The lack of continuity makes these facets less concerning, but warrant an examination before heading onto large or unsupported terrain features on northerly slopes. Below the recent snow layers, you might find alternating crusts and snow layers.  Although observers found a slightly reactive layer of graupel down 22", we don't expect avalanches to fail below the early March crust.  In the Maggies area total snow depth is around 86-118" between 4000-5000 ft.

While storm slabs were present on Thursday, they were shallow and should be gaining some strength by Friday as we are not expecting much more snow or wind loading. Most of the recent snowfall has already been redistributed onto lee slopes (N and E aspects).

Cornices and swails have grown in size in the past week. Give freshly formed cornices a wide berth while traveling along ridgelines, they may break back further than you expect. They can also help you identify recently wind-loaded avalanche start zones to the lee of the ridgelines.

2021-22 Forecast Schedule: Avalanchedanger ratings will be issued for the Olympics every Friday through Sunday and during mid-week holidays. During the week when the Hurricane Ridge road is closed, forecast information will be updated daily to include expected conditions and relevant travel advice under the No Rating label.

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