Bollettino valanghe

Continental

Valdez Avalanche Center
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In sintesi

The avalanche hazard is Moderate above 4000'.  Shallow storm slabs are beginning to develop as heavy snow is expected to develop tonight.  Human triggered avalanches may become possible at upper elevations where more snow is able to accumulate and  winds build deeper slabs.  The hazard is low below 4000' where only a couple inches of snow is expected today that will accumulate on very hard wind affected snow.

The hazard will be higher at lower elevations if heavy snow arrives earlier than forecasted.

 

 

Problemi valanghivi

  • Storm Slabs

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

    A pattern change is currently underway with light snow falling and a trace of accumulation from the coast to 46 mile as of 6am.  Snowfall is expected to be light today with accumulations not expected to exceed 3 inches.  Snowfall is forecasted to become heavy by this evening, an increase in the avalanche hazard will coincide with the onset of heavy precipitation.  Shallow human triggered avalanches may be possible at upper elevations where snowfall amounts are slightly higher and ridgetop winds build deeper slabs.

    New snow is falling on a variety of wind affected surfaces that range from old rain crusts below 2500' to sastrugi and very hard smooth wind board.  New snow may have a difficult time bonding to old wind affected snow initially, especially on Thompson Pass and north where temperatures remain below 0.  Our area is not expecting sufficient snowfall today to increase the avalanche hazard.  If we receive more than 4 inches of snow today the hazard will be moderate at all elevations.  Pay attention to new snowfall amounts and how well new snow is bonding to old surfaces.

     

  • 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 occurs 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

Light snowfall today is not expected to be sufficient to increase the avalanche hazard, except maybe at upper elevations where higher amounts are possible coupled with moderate winds.  

As heavy snowfall begins the hazard will rapidly increase.  On 1/25 surface snow was found to be variable with 6-12 inch sastrugi in places creating a rough bed surface.  Other places very hard and smooth wind board was observed with very small (< .5 mm) facets present on top.  In these areas a low friction bed surface exists that new snow may bond poorly to initially.  

As new snow accumulates more than 6 inches we should assume that the new snow is initially having a hard time sticking to the old snow until we prove differently.  Pay attention to new snow amounts and use hand shear tests to determine how well new snow is bonding.

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: 52 inches

Thompson Pass snowfall data is currently unavailable

46 mile height of snowpack: 66 inches

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