Avalanche forecast

Continental

Valdez Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

 The avalanche hazard is moderate above 2000' and low below.  Heightened avalanche conditions exist on specific terrain features.  Human triggered avalanche are possible 1-3 feet in depth.  Instabilities may exist in steep terrain and on specific terrain features that have been loaded by recent wind.  Watch for signs of instability such as shooting cracks and collapsing.

Avalanche problems

  • Storm Slabs

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

    Our forecast area has been receiving nearly continous snowfall over the last couple of weeks. Settled storm slabs up to 3 feet in depth have been observed.   Storm snow has been found to be right side up and stable in most locations.  The exception to this has been in areas where the wind has redistributed the new snow into stiffer slabs .  

    The main concern today for people recreating in avalanche terrain will be areas where the wind has moved the storm snow into deeper and stiffer pockets.  Wind loaded snow was observed in specific locations on 12/21.  Signs of instability were present were the  snow was hard over soft at the surface.  These wind loaded pockets were ~4" deep at mid elevations and ~ 10" deep above 5000'.  Watch for shooting cracks or collapsing, these are both indicators of unstable snow.  

    Winds were moderate out of the north yesterday but have switched back to southerly today.  Wind loaded storm slabs could exist on a variety of aspects.

    Avoid terrain traps and slopes steeper than 32° were upside down storm slabs exist (hard snow over soft).  

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3

    Faceting below the Thanksgiving day crust has been observed in the continental zone below 4000'.  Stability tests have shown stubborn results although propagation has been observed when the ECT tests are overloaded (ECTP 30++).  Shears at this failure plane are not clean.  This is a low probability high consequence avalanche problem.

    This layer is worth mention since there is ~3 feet of settled storm snow sitting on top of it.  Triggering an avalanche at this layer would be large enough to injure, bury or kill a person.

    The current thinking is that this avalanche problem is only a concern at mid elevations in the continental zone (2-4000').  Below 2000' a strong melt freeze crust exists near the surface that supports the weight of a person or snowmachine. In the Intermountain and Maritime zone faceting below this crust was insignificant.

    The upcoming storm this weekend will be a good test of the strength of this weak layer.

Avalanche Discussion

Since the last major storm cycle 12/11-12 snowfall has continued to accumulate at a  moderate pace with temperatures remaining fairly steady.  There is currently a lot of snow available for transport, allowing for deeper wind loaded pockets to form in areas exposed to wind .  The main concern for today will be these wind loaded area.  Winds have shifted from north to south overnight.   Wind loaded storm slabs could exist on a variety of aspects.

Near continous snowfall over the last couple weeks has allowed our snowpack to steadily build.  A lack of clear weather windows has prevented persistent weak layers the oppurtunity to form in the upper snowpack.  The exception to this is the far northern part of our forecast zone where some short periods of clear and cold have occurred, although meaningful facet development has not yet been observed.

A stable snowpack has been observed in most locations, with surface instabilities being the main concern.  The only flaw in the snowpack currently is faceting below the Thanksgiving day crust in the continental zone.  A deep persistent weak layer problem has been listed in this zone, although skier triggered avalanches are unlikely at this layer.  

The hazard is low below 2000' where 3-6 inches of uncohesive snow sits atop a strong melt freeze crust.

Regions covered