Bollettino valanghe

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Valdez Avalanche Center
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In sintesi

The avalanche hazard is low at all elevations.   Human triggered avalanches are unlikely.  Recently wind loaded snow has gained strength and is unreactive to human tritriggers in most locations.  Natural avalanches are unlikely.

Avalanche forecasts are issued Wednesday- Sunday.  The next avalanche forecast will be issued on 1/24.

 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1.5–2.5

    Wind slabs that have formed over the last week have gained strength and will be unlikely to trigger by a person or machine.  Wind slabs will have a hollow drum like feel.  Signs of instability will likely no longer be present but if they are, realize that unstable snow remains in that location.

    Moderate to strong north wind will continue today. At 5 am Thompson Pass was -3° F with 60 mph north wind, this is creating dangerous wind chill values in the -30 to -40 range.  The wind that occurrs today is expected to have minimal affect on the snow.  Significant stripping and redistribution of the snow surface has already occurred and there is no longer any loose snow available for transport.    Some high elevation ridges may continue to see snow transport although this is expected to be minimal.

     

    Wind chill chart

  • Glide Cracks

    • Tutte le quote
    Probabilità
    Unlikely
    Dimensione
    2.5–3

     Glide avalanches are a strange beast that act differntly than other avalanche problems.  Full depth failure can occur independent of snowpack stability.  Or in other words, they can release even when a stable snowpack is in place.

    Since it is not possible to time their sensitivity the only way to mitigate this hazard is by avoidance.  First identify where glide cracks exist and avoid spending time beneath them.  Glide cracks are easy to identify.  They look like crevasses, but exist in non glaciated terrain.

    These do not produce small avalanches,  but rather failure will include the entire snowpack.  

    Glide release on Town mountain

    Photo: Rich Lofton

Avalanche Discussion

The avalanche story continues to revolve around north wind.

Strong north wind has been affecting our area for the last 5 days.  During the beginning of this cycle, 60-90 mph north wind moved loose snow across the landscape forming wind deposits (slabs) in low areas and lee slopes.  Many areas were stripped down to older snow surfaces.  The strength of the wind that has occurred created a lot of sublimation ( snow moves from solid to gas state) at high elevations.  In other words, snow that blew off high elevation ridges never hit the ground again in some places.  A lot of redistribution happened at mid to low elevations,  although a major net loss in the mass of our snowpack has occurred at upper elevations.

As wind slabs initially formed they were sensitive with some natural avalanche activity observed in all three forecast zones, mostly on southerly aspects.  Facets exist underneath wind slabs in some locations which promoted wide propagations in a few places.  As time has moved forward wind slabs quickly became very hard and unreactive to human triggers.  North winds will continue through at least mid week, but without loose snow available for transport the effect on the snowpack is expected to be minimal unless gusts become stronger than what occurred on 1/17 (90 mph), although this is unlikely.

Glide cracks have been observed in all three forecast zones.  Avoid travelling beneath these as full depth avalanches can release unexpectedly.

Valdez season snowfall: 170 inches

Valdez January snowfall: 26 inches

Valdez height of snowpack: 62 inches

Thompson Pass snowfall data is currently unavailable

46 mile height of snowpack: 66 inches

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