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.  Triggering a windslab avalanche on recently wind loaded slopes  1-2+ feet in depth remains possible.  Natural avalanches are unlikely.

The hazard will be lower in areas unaffected by wind.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2.5

    Strong north winds are expected to continue today.  Most of the redistribution of surface snow has already occurred as wind gusts are not expected to exceed the peak gusts of 1/17.  Although, continued flagging along high elevation ridge lines will likely continue.  Some natural avalanche activity has been reported  on south aspects over the last 36 hours including: Hippie Ridge, South Three Pigs and road cuts near the hairpin turn, these were all D1.5-2.5 in size.

    Wind slabs are becoming less sensitive to human triggers as they become stiffer with time.  Even though the sensitivity is going down the consequence of triggering one of these wind slabs can still be significant.  Wind slab failure at this point would be more likely to occur on larger slopes and would likely fail behind a person or machine rather than at your feet.  Stiffer wind slabs  have the potential for wider propagation.  This is in contrast to when wind slabs first form and many smaller slopes are reactive.  

    There is the potential that buried facets exist under wind slabs in some locations.  This would make triggering an avalanche more likely and may allow this hazard to  persist (see problem  2).   The strength of recent wind will leave many areas stripped down to old snow.  These locations will be safer than those were recent wind deposits (slabs) exist.  Wind slabs will have a hollow drum like feel and a pillowed look.  Avoid areas receiving active wind loading and watch for signs of instability such as shooting cracks, collapsing and recent avalanche activity.

     

    Natural wind slab avalanche that released on road cut near hairpin turn.

    Photo: Kyle Sobek

  • Persistent Slabs

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

    Faceted snow exists in specific locations about a foot down in all three forecast zones that was created by the mostly dry weather since 12/25.   These facets have been found to be rounding to some extent and mixed with other grain types, although remain a concern.  The distribution of this layer is not widespread due to previous north wind on 1/9 that removed it from windward slopes in wind exposed terrain.  It is likely that the strong winds that have occurred over the last 48 hours will have removed/ blown away this weak layer in more places.  

    In multiple locations, this weak layer exists underneath wind slabs formed by the moderate 1/9 outflow event.  The major questions moving forward will be:

    1) Is the wind slab above these facets strong enough to withstand the damage that is going to occur with strong winds and leave faceted snow preserved?

    2) Where could this layer of facets possibly stay preserved.

    The first question we will have to wait and see the full effect of the current outflow event.  As for the second, facets will be most likely to remain in protected areas.  These can exist as you move further away from the Thompson Pass/ Lowe river valley corridors, where winds are less severe.  Digging snowpits will be the best way to identify the presence of this layer in protected areas moving forward.  This process can be complicated and often misleading as this layer can be difficult to identify and spatially variable

    The presence of this layer will increase the odds and potential propagation length of human triggered and natural avalanches today.

    Rounding facets mixed with other grain types found beneath wind slab on Billy Mitchell 1/16. Down 30-40 cms ~3600'.

    Photo: Gareth Brown

  • Glide Cracks

    • All elevations
    Likelihood
    Unlikely
    Size
    2.5–3

     Glide avalanches are a strange beast that act differntly than other avalanche problems.  Full depth failure can occur 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

Wind slabs are gaining strenghth with time.  The possibility to trigger one of these slabs still remains due to the possibillity of continued wind loading and faceted snow that exists 1-2 feet beneath the surface in specific locations.  The consequences of triggering a wind slab avalanche at this point is high.  This is due to the density of debris that would be involved, and the potential for wide propagations with a stiffer slab character, along with the potential presence of weak snow (facets) beneath wind slabs.

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: 62 inches

Thompson Pass snowfall data is currently unavailable

46 mile height of snowpack: 66 inches

Regions covered