Bollettino valanghe

Maritime

Valdez Avalanche Center
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Pericolo valanghe

Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The avalanche hazard is Considerable above 1500'.  Higher snowfall rates overnight will create areas of unstable snow.  Human triggered avalanches are likely 1-2 feet in depth. Natural avalanches are possible.  

Problemi valanghivi

  • Storm Slabs

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

    Thompson Pass received heavy snowfall overnight with 10" reported at 6 am that mostly accumulated between 1-5am.  A previously gradually building storm slab is now under stress with snowfall rates of 2"/ hour.  Winds were light, but deeper loaded pockets can still be expected along high elevation ridges and the lee side of wind channeled terrain.  Storm slabs are now expected to be 8-18" in depth depending upon elevation and proximity to the coast, with the higher amounts towards the Maritime snow climate zone.  These storm slabs are sitting on buried surface hoar in some places.  It is expected that this layer does not extend much above brush line in most places, however was identified as intact at 3800' on Crudbusters in the Continental zone on 12/26.  There is a moderate amount of uncertainty in the 12/22 buried surface hoar distribution which has led to a Considerable hazard rating this morning.

    Snowpack assessment is now less straightforward.  Storm slab amounts are now getting to the point where buried surface hoar is being put under stress where it exists.  In this situation, slab character and depth of new snow can make the difference in stability and could vary even along a single slope. EX: Stable conditions may continue to exist where new snow remains uncohesive and be reactive on a rollover where slightly more storm wind has created stiffer surface snow.  Identifying buried surface hoar can be tricky as it can be easily missed in snowpits and may produce false stable results.  It is unknown whether this weak layer exists in the Maritime zone.

    In areas where the 12/22 layer does not exist instabilitis will be possible in steeper terrain, especially in areas loaded deeper by wind.  Watch for signs of instability, such as shooting cracks that could indicate the presence of a weak layer.  Pay attention to the amount of new snow that exists and the stiffness of the slab.  The stiffer the surface snow is, the more propagation potential there is.

    The hazard is expected to remain steady today as a few inches of snow is expected to accumulate with light winds.

     

Avalanche Discussion

Observed Avalanche Activity last 72 hours: 

UNKNOWN/ cloudy conditions has prevented the ability to observe avalanche activity

1-2 feet of snow now sits on the 12/10 rain crust.  This rain crust is showing signs of breaking down and could act as a weak layer in the future.  This crust has been found pretty consistently to be fairly thick up to 3000' and then slowly taper and disappear by 3500'.  There have been reports from the Maritime zone that crust extends up to 4000' in the Port of Valdez.  In between the surface and the 12/10 rain crust is a layer of surface hoar that was buried on 12/22.  This layer has not yet shown signs of propagation in stability tests, but this is likely due to insufficient amount of snow above and lack of cohesion (no slab) in the areas tested.  This situation has changed a bit overnight with heavy snowfall rates on Thompson Pass resulting in 10" of snow reported.  This has increased stress over this layer and may potentially increase sensitivity.  

Winds were light to moderate and mostly southerly during the last few days.  Watch for areas where the surface snow is stiffer at the surface, indicating wind redistribution.  .  It will be possible to encounter areas of unstable snow today where the new snow has been loaded deeper by recent wind or where buried surface hoar exists.

Continue to avoid Glide cracks in the area where they exist from Nick's Buttress through Cracked Ice at mid elevation.

If you travel in the Continental zone today, exercise extra caution as there is very limited field data from this location.  It is unclear as to whether deep slab instabilities exist, however it is a possibility.

If you get out in the mountains today consider leaving an observation to help increase the understanding of current snowpack stability.  

A weather and snowpack season history is available by clicking on the Weather History tab that is located above the bottom line statement once you have entered the full forecast.

Season Snowfall Data

Location 24 hour Snowfall Inches- 12/27 24 hour Snow Water Equivalent Inches Height of Snow December Snowfall Season Total Snowfall Valdez 4    N/O         27     35 Thompson Pass    10 N/O   N/O    N/O    N/O Nicks    2 N/O    50    27 N/O 46 Mile    Trace   N/O   22    10 N/O

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