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.  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

    North wind yesterday was forming fresh wind slabs in terrain that is very close to Thompson Pass.  Terrain that was slightly removed from the gap remained calm with no upper elevation flagging observed.  This weather is expected to continue with gap winds expected to be in the 30's from the north and ridge top winds to be light in the single digits.  The main concern today will be wind slabs that have formed in the last 24 hours in terrain close to the gap of Thompson Pass and other wind channeled terrain.  Pockets of wind slab may also exist below high elevation ridgelines in places.

    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.  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.

    A trace of new snowfall is expected by tonight, but is not expected to be a sufficient amount to increase the avalanche hazard.

     

  • 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

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Avalanche Activity last 72 hours: 

-D2 natural soft slab observed in the back of Gully 2 that released from steep terrain on a North aspect.  May have been initiated by cornice fall

-D2 natural soft slab debris was observed on a South aspect of Max High that likely occured during the 12/15 snowfall.  Crown had been filled back in and was not visible.

Watch out today for freshly formed wind slabs.  Areas where active snow transport has recently or is currently happening are the primary concern today.  Wind redistribution was observed in close relation to the Thompson Pass Summit, but was calm elsewhere.  Pockets of wind slab may exist along high elevation ridgelines as well as other wind channeled terrain.  Pay attention to 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 this evening but is not expected to be enough to effect stability.

New snow from 12/15 has settled down to about 14 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.

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.

Season Snowfall Data

Location 24 hour Snowfall Inches- 12/19 24 hour Snow Water Equivalent Inches Height of Snow December Snowfall Season Total Snowfall Valdez    0 N/O       Thompson Pass    0 N/O N/O    25    141 Nicks    0 N/O    41    22 N/O 46 Mile    0   N/O   14    4 N/O

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