Lawinenlagebericht

Continental

Valdez Avalanche Center
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Lawinengefahr

Hochgebirge
1 · Gering
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 3 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The avalanche hazard is low at all elevations.  Very hard wind affected snow surfaces exist that are unlikely for a person or machine to trigger.  Natural avalanches are unlikely.

 

 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    1.5–2.5

    It has been 8 days since strong north winds began to affect our area.  Wind slabs that have formed during that time have gained strength and have become unreactive to human triggers even though they overlie facets in some locations.  The strength/hardness of wind slabs in most places does not allow any ski penetration making initiating an avalanche very unlikely.  

    Protected snow has been observed in isolated locations at low elevation as recently as 1/24.  Near surface facets have been observed at the surface in protected terrain that will be a concern moving forward in isolated areas once new snowfall arrives.  

    North winds have decreased in strength and distribution over the last 24 hours and temperatures have dropped with Thompson Pass at -12 at 6 am.  Dangerous wind chill values can still be encountered today in wind exposed areas .  The wind has done its damage and further wind slab developement is not expected.

    Upper and mid elevations stripped to bare ground in wind channeled terrain. 1/23

    Photo: Gareth Brown

  • Glide Cracks

    • Alle Höhenlagen
    Wahrscheinlichkeit
    Unlikely
    Größe
    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

A wind damaged snowpack is currently in place created by strong north winds over the last 8 days.  Wind slabs have been observed to be pencil to knife hard and unreactive to human triggers.  Facets exist underneath slabs in some locations.  This was evidenced by some widely propagating natural avalanches that occurred as wind slabs initially formed on 1/17.  These facets are now bridged by the knife hard slabs mentioned above.  The upper elevation snowpack has lost a significant amount of mass.  Significant stripping of the snow surface occurred and instead of being redeposited, a lot of snow sublimated (turned from a solid directly to a gas) due to the strength of the wind.

Moving forward the concentration will be on how well will new snow that is forecasted for the weekend, bonds to these wind damaged surfaces.  The answer to this will likely not be a simple one.  The temperature when snowfall begins will be a factor, warmer temps will promote bonding whereas colder locations will slow this process.  Another factor will be the amount of brake down (faceting) that has occurred of the windboard.  Strong winds are continuing and will remove this faceted snow in exposed and channeled terrain.  Flagging that has occurred over the last couple days is likely the removal of small facets forming on the windboard.  Winds have been easing in strength and decreased in their effect spatially (affecting a smaller portion of terrain).  This may allow a small layer of weak snow to form and be preserved atop wind slabs in protected areas that would make future storm slabs more sensitive in specific locations.  To confuse things further,  there are areas at low elevations that have been protected from recent wind.  These are islolated, but have been observed as recently as 1/24 in Keystone canyon.  In these locations the surface consists of near surface facets, this will be a weak layer once sufficient snowfall accumulates on top to make a slab.  

Valdez has only received 30 inches of snow in the last 30 days and Thompson Pass probably half of that.  A pattern change is looking likely this weekend with the potential for heavy snowfall and increased avalanche hazard.

LET IT SNOW!!!!

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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