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 feet.  Human triggered avalanches are possible today 1-2 feet in depth where moderate North winds have formed fresh wind slabs.  These areas are currently limited to terrain close to Thompson Pass and other wind channeled terrain.  Natural avalanches are unlikely.

Avalanche problems

  • Wind Slabs

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

    Conditions will be similar to yesterday as moderate North winds near Thompson Pass are expected.  Wind speeds showed a steady decrease overnight across the forecast area. However, Thompson Pass winds are expected to return to speeds in the 30s as a front approaches our area.  Very little, if any, precipitation is expected during the day today.  Unless winds exceed the strength of yesterday, additional wind slab formation is not expected during the day today.  This will allow the wind slabs that are in place to become less sensitive.  It will still be possible to trigger these wind slabs in areas close to Thompson Pass or other wind channeled terrain.

    Pay attention to the amount of wind redistribution that has occurred in the area you choose to travel.  This can be determined by looking for snow that is stiffer at the surface than what is below and a difference in the depth of surface snow.  Wind slabs that are in place will likely now have a hollow drum like feel.  In areas where stiffer snow is present at the surface human triggered avalanches will be possible 1-2 feet in depth, especially in convex and cross-loaded terrain.  Watch for signs of instability such as shooting cracks and collapsing that would indicate the presence of unstable snow.

     

     

  • Glide Cracks

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–2.5

    Numerous Glide Cracks exist on the North facing Buttressess of Nicks through Cracked Ice between 2000'-3000'.  Identify where these are if you decide to travel in this area and avoid traveling on or below them.  Glide cracks act differently than all the other avalanche problems and can fail even when the general hazard is low and without signs of instability.  Stability of Glide cracks has more to do with the relationship with the friction at the ground and less so to do with the weather that is effecting the surface like other avalanche problems.  Little is known about assessing glide cracks, so travel advice is simple: Avoid them.

    Numerous Glide Cracks on the Cracked Ice Buttress

    Photo: Kyle Sobek

Avalanche Discussion

Avalanche Activity last 72 hours: 

NONE

A rare period of benign December weather continues today, which should allow wind slabs that have formed near Thompson Pass to settle and become more stubborn to human triggers.  A shortwave front moves north from a low in Bristol Bay that should bring an increase to the wind this evening, with precipitation staying to our west.  Expect a variety of wind directions with the increase in winds.  Overall flow is Easterly, which should occur at upper elevations with surface winds at Thompson Pass remaining North as the arctic air to the north of the pass does battle with the incoming surge of warm and moist incoming pacific air.

Our main concern continues to be wind slabs that could be up to 2 feet deep in terrain that is directly affected by Thompson Pass Gap winds.  Wind redistribution was observed in close relation to the Thompson Pass Summit, but was calmer elsewhere.  Pockets of wind slab may exist along high elevation ridgelines as well as other wind channeled terrain.  Pay attention to the slab character at the surface ( has the snow formed a cohesive layer?). Seek out areas that are sheltered from the current and recent wind, as these areas will not only provide better stability but also better riding quality.  A trace of new snow is expected today but is not expected to be enough to affect stability.

New snow from 12/15 has settled down to about 10-12 inches but remains uncohesive in wind protected areas.  The interface of the new/old varies depending upon elevation.  Below 3500' a rain crust that formed on 12/10 exists.  In these areas hand shear tests are becoming more resistant, with good stability observed.  Above 3500' the interface consists of old dry snow with resistant hand shear tests and moderate ECT scores and no propagation.

Surface Hoar formation was observed below brushline on 12/18 in the Gully 2 area up to 1.5 cm.  This will be a concern with future snowfall in isolated areas where open slopes exist below brushline.  Most areas below brushline still have very thick vegetation which will likely limit this future problem.  A strong inversion is currently in place with temperatures in the Tsaina Valley bottoming out at -12F yesterday with the Nicks station in the mid 20's.  Temperatures are on the increase with valley bottoms rising above 0 and Nicks at 31° at 5am.  This weather will continue to drive surface hoar formation at low elevations that are wind protected, but is unlikely to exist at upper elevation start zones.

Continue to avoid Glide cracks in the area where they exist from Nick's Buttress through Cracked Ice at mid elevation.

If you travel in the Continental zone today, exercise extra caution as there is very limited field data from this location.  It is unclear as to whether deep slab instabilities exist, however it is a possibility.

If you get out in the mountains today consider leaving an observation to help increase the understanding of current snowpack stability.  

A weather and snowpack season history is available by clicking on the Weather History tab that is located above the bottom line statement once you have entered the full forecast.

Season Snowfall Data

Location 24 hour Snowfall Inches- 12/20 24 hour Snow Water Equivalent Inches Height of Snow December Snowfall Season Total Snowfall Valdez    0 N/O    12     27     35 Thompson Pass    0 N/O   N/O    N/O    N/O Nicks    0 N/O    41    22 N/O 46 Mile    0   N/O   14    4 N/O

Regions covered