Bollettino valanghe

Northwest Coastal

Dec 13 – 14, 2012Avalanche Canada
Vedi sulla mappa
Archiviato · scaduto 14 years ago

Pericolo valanghe

Sat
Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
Apri la mappa completa

In sintesi

Avalanche danger may spike to HIGH in the alpine if stormy weather arrives sooner than forecast on Friday.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible - Likely
    Dimensione
    1–5
    Storm slabs are likely to be encountered on many slopes. Be alert for new and buried wind slabs behind ridges and ribs. Storm/wind slabs could step down to trigger a persistent weakness, creating a very large avalanche.

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–8
    A deeply buried facet/crust weakness exists. Very large and destructive avalanches may be triggered  from thin snowpack areas or by heavy loads such as a storm slab stepping down, or a snowmobile spinning its tracks.

Confidence

Poor - Timing of incoming weather is uncertain for the entire period

Weather Forecast

Friday: Strong W to SW winds. Alpine temp -6. Light snow starting late in the day.Saturday: Strong to gale SW winds. Alpine temp -6. Moderate to heavy snow. Sunday: Light SE winds. Alpine temp -12. Light snow.The timing of frontal systems affecting the region is uncertain, especially on Sunday.

Avalanche Summary

On Wednesday, explosives triggered a size 3 slab which failed at the base of the snowpack on glacial ice. Several storm/wind slabs to size 2 were also triggered by explosives. A widespread natural cycle occurred on Monday/Tuesday with avalanches to size 2.5 running in steep terrain at treeline and alpine elevations. Explosives testing on Tuesday produced several very large (size 3-4) slabs on northerly aspects near Stewart. These failed on basal facets and/or glacial ice and were up to 4 m deep and 250-300 m wide. Storm/wind slabs also stepped down to basal facets. Low elevation steep terrain also was shedding numerous small, moist loose avalanches during Monday/Tuesday’s warming.

Snowpack Summary

Storm snow instabilities are likely to continue developing over the next few days as variable new snow layers build up. Spotty surface hoar is also buried in the upper snowpack, particularly in sheltered treeline areas. New and buried wind slabs are widespread and exist on a variety of alpine and exposed treeline slopes due to variable winds. Of key concern is a November facet/crust layer which can be found near the base of the snowpack. This layer, which is widespread, can be triggered from thin-spot trigger points, or with a heavy load, such as storm slabs stepping down, cornice fall or a snowmobile. It has the potential for very large, destructive avalanches and demands respect. A rain crust is buried in the upper snowpack at low elevations. In general the snowpack is highly variable in depth due to windy conditions this season.

Regioni coperte