Avalanche forecast

Continental

Valdez Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

The avalanche hazard is Considerable above 2000 feet and Moderate below.  Weak snow exists in specific locations beneath 2-3 feet of settled storm snow.  Human triggered avalanches will be likely today in these locations. A trace of snowfall with increasing north winds will begin to create wind loaded snow on lee aspects.  Snowpack assessment is recommended as  stability will vary depending upon location.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–3

    The 2/20-22 storm cycle left us with 2-3 feet of settled snow and a widespread natural avalanche cycle on 2/22.  This cycle was triggered by intense snowfall rates and strong southerly winds at the tail end of the storm.  Some naturals had very wide propagations associated that indicate surface hoar that formed during the clear weather of 2/14-16 was buried intact in specific locations and has acted as a weak layer.  Other naturals appear to be simple overloading of the upper snowpack by snow and south wind.  Surface Hoar is expected to be varied in its distribution which will make stability assessment challenging moving forward.

    After 2 clear nights, storm slabs will be settling lowering the likelihood of avalanches.  With this settlement also comes an increase in cohesion of the storm snow which can create longer propagations of avalanches that are initiated.  A trace of snow is expected later in the day that will be accompanied by increasing north winds that will create an additional avalanche problem (see problem 2).  A considerable hazard rating has been maintained today due to human triggers being likely in steep terrain where surface hoar exists.  The mass of snow that could be involved with human triggered avalanches today reaffirms a considerable rating.

    As mentioned above some areas will likely see improving stability today.  This will not be the case for all slopes,  if you experience positive results today in one area, don't assume all areas to be the same.  Assessment should be carried out on a slope by slope basis until more information about surface hoar distribution can be gathered and more time for settlement has occurred.  Digging snow pits will be the best tool today for snowpack assessment as the depth of storm slabs may prevent signs of instability from occurring.  Snow pits should not be used to tell you what slopes to travel on, but rather what slopes to avoid.  Pay attention to any signs of instability that do occur such as natural avalanche activity on similar aspects and elevation, shooting cracks, and collapsing.

     

    Natural avalanche 2/22 North Three Pigs

    Photo: Gareth Brown

  • Wind Slabs

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

    North winds are forecasted to begin at some point this afternoon and become moderate.  There is a significant amount of snow available for transport that will easily form fresh wind slabs on the lee side of high elevation ridges, terrain features and cross loaded gullies.  Human triggered wind slab avalanches will be possible today up to 1 foot in depth and will have the potential to step down to the storm snow interface making much larger avalanches.

    Avoid slopes steeper than 30° that are receiving active wind loading.

Avalanche Discussion

We are less than 48 hours removed from a very active natural avalanche cycle with the most widespread activity of the season.  Some of the natural activity had long propagations that involved a layer of surface hoar that was buried on 2/17.  This layer of surface hoar is believed to be very spotty in distribution which will make assessment challenging.  Expect this layer to exist in commonly wind protected basins.  Two D1 skier triggered avalanches were reported yesterday that failed on this layer in the mid elevations of the Iguana backs area.  A couple of deep slab outlier naturals were also observed in Nicks valley and Cauliflowers.

Other activity that was observed such as North Odessey Gully and North Dimond are expected to be more of a simple overloading of the snowpack by high snowfall rates and strong wind loading.  Natural activity was more pronounced to the north and less so towards the coast.  

Settlement of the storm snow will allow an increase in stability in areas where surface hoar is not present.  This settlement also increases the cohesion of storm slabs allowing for wider propagations of human triggered avalanches.  Human triggered avalanches are likely today in terrain steeper than 32° at mid and upper elevations where the 2/17 buried surface hoar layer exists.  Human triggered avalanches remain possible where this layer is lacking.  Careful snowpack assessment is encouraged and along with conservative terrain choices as a spotty distribution of a weak layer makes asssessment chalenging.

A rain crust exist up to 2000-2500'.  Below this around a foot of settled storm snow exists on top of the crust.  Surface hoar will not be present where a rain crust is present as warm temps and rain on snow would have destroyed the above mentioned weak layer.

North winds will begin today along with a trace of snow, this will start to form a new avalanche problem.  Pay attention to the degree of wind redistribution that is occurring and avoid slopes steeper than 30° that are being actively loaded.

 

Valdez season snowfall: 240  inches

Valdez February snowfall: 34 inches

Valdez height of snowpack: 84 inches

Thompson Pass snowfall data is currently unavailable

46 mile height of snowpack: 76 inches

 

 

 

 

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