Bollettino valanghe

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Valdez Avalanche Center
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2 · Moderato
Limite del bosco
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In sintesi

Today you will find a Moderate avalanche hazard at all elevations. Human-triggered avalanches 1-3 feet deep will be possible above 3000 feet. Lower elevations will have the possibility of producing small natural or human-triggered wet loose avalanches as temperatures warm today. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Our main concern today is triggering an avalanche 1-3 feet deep involving old storm snow from last weekend. A layer of surface hoar was observed on 3/29  and is now buried under 1-3 feet of storm snow that fell Easter weekend.  This buried surface hoard layer is expected to be widespread on Northerly aspects above 3000 feet. Other aspects with cold-protected snow may also have buried surface hoar. 

    Over the last few days, slope tests and observations have shown good stability in popular areas throughout Thompson Pass. Caution is still advised due to the potentially dangerous setup with a slab on top of a persistent weak layer. Areas where the surface snow is stiffer and overlies a hard/smooth bed surface will be the most likely to produce a dangerous avalanche today. Deeper snow totals in some areas (approaching 3 feet) will increase the possibility and consequence of triggering a slide today. 

    Today you can expect the sensitivity of this avalanche problem to vary throughout our forecast area.  Recent snow totals, bed surface characteristics (Hard vs Soft), and slab characteristics (stiff vs unconsolidated) will dictate the sensitivity of persistent slabs. Areas with more than a foot of recent snow or stiff/wind-affected snow will have an increased sensitivity. Hard, smooth surfaces below the 3/29 surface hoar layer will add to this sensitivity in specific areas. Digging hand pits, quick pits, and probing will be good techniques for assessing these variables today. Careful assessment is advised when entering new areas.

    Light snowfall is not expected to affect stability today. Additional snowfall throughout the week may create a more sensitive situation with our persistent slab problem. Stay tuned. 

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Southeast winds have redistributed recent storm snow at ridgetops. Shallow wind slabs at upper elevations are expected to be gaining strength but there is still the possibility of triggering a small to large avalanche in specific areas. If you travel in higher elevations today pay attention to the stiffness, depth, and extent of wind slabs. Thinner slabs could propagate into deeper areas or step down to our persistent slab layer creating a dangerous avalanche. 

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Wet loose avalanches will be on our radar for the rest of the spring season.  Cooler temperatures and a lack of solar warming will likely limit this problem today.  If it rains or becomes warmer than forecasted we can expect an increase in wet loose activity. Avoiding steep low elevations with saturated snow is recommended. 

Avalanche Discussion

RECENT AVALANCHE ACTIVITY:  

Several large (D2-3)  human-triggered and natural avalanches have been reported in the last 72 hours that failed on buried surface hoar.  Multiple D2-3 natural avalanches have been observed that likely failed last weekend during the last storm including one deeper crown of 3+ feet in the Tonsina on Japanese Wall.  Several wet loose up to size 2 have been observed on steep solar aspects as well.

DISCUSSION:

Avalanche hazards today are focused on recent storm snow from last weekend. Snow totals from 4 - 24+ inches will be found depending on elevation and proximity to the coast. High elevation Nort facing slopes above the Port have been observed to have the highest totals. 

The Thompson Pass corridor and areas further inland will likely have buried surface hoar beneath varying amounts of recent storm snow. This situation will be most prevalent on Northerly aspects. User testing over the last couple of days has produced little significant avalanche activity in popular areas but this does not necessarily indicate widespread good stability. Cautious assessment is advised today. Areas with deeper, stiffer snow overlying surface hoar should be suspect even if avalanches aren't observed. Use test slopes, hand pits, and terrain progression to gather data when entering new areas today. 

Additional Concerns:

This is the time of year when cornices begin to fail.  You can significantly reduce your overall exposure in the mountains this time of year by avoiding traveling on top of or under cornices.

A very significant Glide avalanche/ landslide in Upper Stuart Creek last week is a great reminder of the destructive forces involved with glide crack failure.  Glide cracks exist in isolated areas and will be a hazard throughout the season until they fail.  Avoid exposure to glide cracks.

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