Bulletin d’avalanche

Continental

Valdez Avalanche Center
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Danger d’avalanche

Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

The avalanche hazard is Moderate at all elevations.  North wind today will create the potential for human triggered wind slab avalanches in specific terrain.  Natural and human triggered  wet loose avalanches will be  likely during the heat of the day on solar aspects.

Public avalanche forecasts are issued Wednesday-Sunday.  The next avalanche forecast will be issued on 4/17.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Wind /storm slabs have been reported to be sensitive to human triggers yesterday with multiple D2 avalanches reported up to 20 inches in depth.  The sensitivity of new and wind stiffened snow is to be expected yesterday as a prolonged period of incremental snowfall had just recently come to an end and the upper snowpack was still adjusting.  Sensitivity of the new snow will be decreasing in areas that are protected from north winds that are forecasted to become moderate during the day.  

    New wind slabs will be developing in areas that experience north winds of 20-30 mph today.  Where new wind slabs develop, it will be possible for a person or machine to trigger an avalanche up to 2 feet in depth.  There is currently an abundant amount of soft snow available for transport on northerly aspects which will allow wind slabs to easily form where strong winds are occurring.  Today's wind is not expected to have a widespread effect, but rather create a new avalanche problem in specific areas which would include the lee side of upper elevation ridge lines in wind channeled terrain.   Pay attention to the amount of wind redistribution that is occurring in the areas you choose to travel.  Avoid steep terrain that has been recently loaded by north wind as it will be possible to encounter unstable snow.   Direct sun may increase the sensitivity of freshly formed wind slabs 

    Older wind slabs that formed on 4/10-11 will be masked by new snow, making them more difficult to identify.  These older wind slabs are expected to have gained strength, however, may still be possible to trigger in upper elevation start zones.  

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2.5

    Wet loose avalanche activity will be likely today.  Fresh snow that has fallen over the last few days will be shedding off steep solar aspects during the heat of the day.   Expect all aspects to be affected at low elevations today.  At mid to upper elevations wet loose activity will be possible on solar aspects with East facing slopes being the first to be affected, south will be the next aspect to become affected by the sun and then finally west.  Pay attention to which slopes are being heated up by the sun and to what degree.

    Wet loose conditions are easy to identify.  Once more than a few inches of snow becomes moist-wet (you can easily form a snowball) then wet loose avalanches will become possible both human triggered and natural on steep terrain.   Roller balls and snow snails are a good visual indicator that wet loose is currently an issue.  Plan your route to avoid exposure to steep low elevation slope when the surface is not frozen.

    Avoid travelling on or below steep terrain where more than a few inches of moist snow exists.

    Natural D2 wet loose on solar aspect of Hippie Ridge

    Photo: Gareth Brown

Avalanche Discussion

RECENT AVALANCHE ACTIVITY:  

Multiple D1-D2 human triggered avalanches were reported yesterday that involved the new snow.  These were 1-1.5 feet in depth.  Areas with previous wind effect were observed to have higher sensitivity.  

Last human triggered activity at 3/29 BSH layer was reported on 4/2

DISCUSSION:

Clear weather is forecasted today and will likely continue through mid week.  North winds are forecasted today that will build wind slabs that could be sensitive to human triggers in specific locations where they form.  North winds are forecasted to decrease towards the end of the day.  In areas that are unaffected by north wind, stability is expected to have increased to some extent from yesterday as a night of clear weather will allow recent new snow in the upper snowpack to settle to a degree.  

It will be important to keep in mind that the sun will play a major role in stability today and in the coming days.  Not only can the sun create wet loose avalanche conditions, but surface snow may become more sensitive in steep terrain as the heat of the day can form a more cohesive slab during specific times of the day.  After a prolonged period of cloudy weather and incremental snowfall, the sun is finally here.  This change in weather can put stress on the upper snowpack making human triggered avalanches possible in steep terrain during specific times of the day.

The 3/29 buried surface hoar layer is now considered to be dormant and very unlikely to encounter.  It has been removed from our list of problems as there have not been any reported avalanches on this layer since 4/2.

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.

Valdez season snowfall: 286  inches

Valdez April snowfall: 11 inches

Valdez height of snowpack: 69 inches

Thompson Pass season snowfall: 698 inches as of 4/5

46 mile height of snowpack: 66 inches

 

Régions couvertes