Avalanche forecast

Continental

Valdez Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

The avalanche hazard is Moderate at all elevations.  Human triggered avalanches are possible in wind affected areas, which may step down to deeper  layers in the snowpack. Natural avalanches are unlikely.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Over the last three days of clear weather, winds have been generally light, however terrain that is close to Thompson Pass has seen moderate North wind.  With low snow coverage down low, the terrain near Thompson Pass is the most reasonable access for most users.  Wind slabs up to 1 foot in depth were observed near Thompson Pass and were stubborn to triggers on 12/31.  A skier or machine in steep terrain could still trigger these wind slabs.  Convex slopes will be the most suspect.

    A surface wind slab will have the potential to step down to deeper layers in the snowpack (see problem 2)

    Wind slabs are now a few days old and will have a hollow drum-like feel.  Watch for signs of instability such as shooting cracks or collapsing that would indicate unstable snow

     

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    There is a layer of buried surface hoar from 12/22 that can be found abouut 16 inches below the surface of the snow in low, mid and in some places upper elevations.  Over the last few days observations have found this layer is being absorbed to some extent by the soft snow beneath.  This is making this weak layer more challenging to identify and when exposed it has been found to be mixed with other grain types.  This lowers the likelihood of human triggered avalanches to be initiated on this layer where this process is occurring.  Stability tests continue to show no propagation with ECTN scores of 18-25.  The concern is that there is a clean shear at this interface and there is uncertatainty about its spatial variability.  

    Even though a handful of observations have been pointing to this layer being less of a concern it will be important to continue to look for and test the sensitivity of this layer.  Buried surface hoar is notorious for remaining weak for long periods of time and catching even the most experienced users off guard.

    Shallower wind slab avalanches will have the potential to exert enough force on the snowpack to cause step down avalanches at this layer.

    (12/26/2024)

    12/22 BSH at 3800' crud

    Photo: Gareth Brown

  • Glide Cracks

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–2.5

    Numerous Glide Cracks exist on the North facing Buttressess of Nicks through Cracked Ice between 2000'-3000'.  Identify where these are if you decide to travel in this area and avoid traveling on or below them.  Glide cracks act differently than all the other avalanche problems and can fail even when the general hazard is low and without signs of instability.  Stability of Glide cracks has more to do with the relationship with the friction at the ground and less so to do with the weather that is effecting the surface like other avalanche problems.  Little is known about assessing glide cracks, so travel advice is simple: Avoid traveling on or below them.

    Numerous Glide Cracks on the Cracked Ice Buttress

    Photo: Kyle Sobek

Avalanche Discussion

Observed Avalanche Activity last 72 hours: 

Numerous D1-2 natural avalanches occurred on Dec28-29, most of which likely failed on Buried surface hoar and were initiated by wind loading or high snowfall rates early morning of the 28th.

The most notable activity was a D3 on the east end of Hippie ridge/ South aspect that initiated at the ridge line and stepped down in multiple places along its path.

Forecast Discussion:

There is quite a bit going on in our snowpack right now with a high degree of spatial variability.  This variability, combined with multiple layers in our snowpack, makes an avalanche forecast that accurately describes a large and variable amount of terrain unrealistic.  Use this avalanche product as a guide to assist in your own assessment depending upon the area you choose to travel.

The last few days of clear and mostly calm weather is allowing the snowpack to settle and gain strength.  Wind slabs have formed in terrain close to the wind funnel of Thompson Pass that have been showing signs of gaining strength and becoming stubborn to triggers.   Areas set back from Thompson Pass have remained calm with dry snow at the surface.

As you look beneath the surface there are three layers that should be monitored by users.

The first and most currently relevant is the 12/22 layer of Buried surface hoar.  A decent amount of natural avalanche activity occurred on 12/28 that is assumed to be attributed with this layer.  This layer was initially very pronounced in snow pits and has been gradually deforming and in the process of being absorbed by the snow beneath.  Even though test results have been pointing towards a lower likelihood of human triggered involvement, this layer remains guilty until proven innocent due to the grain type and the slab above.

Second is a rain crust sandwich with melt forms in the middle that are in the process of faceting.  These rain crusts are from 12/10 and 12/5 and both are showing signs of losing strength.  These crusts go up to 3500' and gradually taper away and dissapear as you gain in elevation.  This layer is not expected to be a current concern as far as human triggered avalanches because the upper crust still maintains some strength and the slab above is thought to be insufficient to overload this layer.  The caveat to this would be that an avalanche that intiates at an upper layer could produce enough force to step down to this layer.  As this layer continues to lose strength and the load above increases, the sensitivity of this layer may increase.

Lastly is the Wind affected snow that formed in Mid-late November.  This layer has been found to be extremelly variable.  It is generally a meter deep in the snowpack with some degree of facets beneath.  The variability lies in the strength and thickness of this layer.  As recently as 12/31 this layer was found close to Thompson Pass to be 20 cms thick and very difficult to shovel through.  In other areas it has been found to be only 5 cms thick and 1 finger hard.  This is another layer that could be a concern in the future, step down avalanches are possible.

Looking into the future fresh surface hoar formation has been noted up to ridgelines.

Additional Information:

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- 1/1 24 hour Snow Water Equivalent Inches Height of Snow January Snowfall Season Total Snowfall Valdez     0 N/O    17     0     35 Thompson Pass    0 N/O   N/O    0    N/O Nicks    0 N/O    53    0 N/O 46 Mile    0   N/O   22    0 N/O

Regions covered