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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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The avalanche hazard is Moderate above 2000 feet and low below.  Human triggered avalanches up to 1 foot in depth are possible in specific areas.  Insatabilities revolve around areas with new and old wind loads.  Natural avalanches are unlikely.

Avalanche problems

  • Wind Slabs

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

    Fresh wind slabs were observed in wind exposed areas of Thompson Pass on 1/12.   These formed overnight 1/11 with 2-4 inches of new snow and moderate southerly winds.  The fresh wind slabs were very soft (fist) and were very sensitive up to 1 foot in depth on test slopes with shooting cracks present.

    Expect these new slabs to only exist in wind exposed terrain and on the lee side of high elevation ridge lines.  Fresh slabs are expected to gain some cohesion overnight (likely 4 finger) and decrease in sensitivity, although remain succeptible to human triggers up to 1 foot in depth in specific locations.

    Recognize which slopes these are present on and avoid terrain traps such as cross loaded gullies in these areas, as well as slopes with consequence.  Watch for signs of instability such as shooting cracks and collapsing that would indicate unstable snow.

     

    Multiple aspects have been loaded over the last week

    Photo: Gareth Brown

  • Persistent Slabs

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

    It has been 72 hours since the last north wind.  Wind slabs have become stiff and in a normal scenario would be unreactive.  Wind slabs that were created on 1/9 were deposited on faceted (weak) snow.  This weak snow will slow the healing process of wind slabs, which will likely be stubborn to triggers today but will remain possible up to 1 foot in depth.

    This type of problem may allow a person well onto the slope before it fails.  The stiffness of the current slab combined with the weak layer may allow failure to occur behind you on a slope .  Avoid traveling above terrain traps and exposure where old wind slabs are present.

    Check for the presence of wind loaded snow in the area you choose to travel.  The effectiveness of small test slopes will be decreasing as small slopes will likely now have good support and lower sensitivity.   Checking for the presence of facets beneath slabs is recommended.   

    The hazard will be lower in areas protected from the latest moderate outflow event.  Seek out sheltered snow for better riding quality and stabiity.  

    Light snowfall along with moderate winds is forecasted during the day, with snowfall expected to increase overnight.  Accumulations in the next 24 hours are expected to be in the 2-4 inche range likely favoring the coastal mountains.  Freezing line may increase to 1000' Sunday morning as a weak jet streak moves overhead.

    Test slope failure at Benzene Alley on 1/9.

    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

The main avalanche concern for today will continue to revolve around wind loaded slopes.  Identifying wind slab location and sensitivity and likelihood has become trickier today.

Wind slabs created by North wind on 1/9 are very stiff (pencil-knife hard) and will be stubborn to triggers but may still be possible to intiate an avalanche.  Triggering an old slab remains a possibility due to faceted snow beneath wind loads.  This variety of wind slab would likely not have signs of instability present, and will no longer fail at your feet but behind a person once they travel out onto the slope and effect a thin spot in the slab.  The likelihood of triggering one of these is lower but the consequence is higher due to the density of the snow it would involve.  These can be indentified as having a hollow drum like feel.

Wind slabs created on 1/11 are much softer (fist- 4 finger) and were created by South wind.  These will likely remain sensitive to triggers today up to 1 foot in depth in wind exposed cross loaded terrain and the lee side of high elevation ridge lines.  This type of wind slab will likely exhibit signs of instability such as shooting cracks and would likely fail at your feet.  These can be indentified by upside down snow (stiffer snow over soft).  Paying attention to aspect will be important today, as it will tell you what type of wind slab you may encounter.

There is a higher degree of uncertainty with the likelihood of triggering old wind slabs as opposed to newly formed ones. 

Light snow may begin today and will pick up in coverage and intensity overnight.  Freezing lines may climb as high as 1000' by Sunday morning briefly before returning to sea level by Sunday night.

Glide cracks have been observed in all three forecast zones.  Avoid travelling beneath these as full depth avalanches can release unexpectedly.

Valdez season snowfall: 162 inches

Valdez January snowfall: 17 inches

Valdez height of snowpack: 57 inches

Thompson Pass snowfall data is currently unavalable

46 mile height of snowpack: 64 inches

Regions covered