Bulletin d’avalanche

Northwest Inland

Feb 19 – 20, 2013Avalanche Canada
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Archivé · expiré 14 years ago

Danger d’avalanche

Thu
Fri
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–5
    The region received a small shot of snow Monday along with east winds.  These reverse winds may have formed soft slabs in unusual locations.  Fresh slabs are likely hiding deep old slabs that may be rider triggerable in steep unsupported terrain.

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–5
    The recent snow and wind have been building cornices on lee features. These cornices are likely weak and may fail at anytime. Cornice failure has the potential to trigger large avalanches.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–7
    Buried beneath the new snow sits a surface hoar/crust/facet weakness down 40 - 100 cm. This may be sensitive to rider triggering in steeper sheltered terrain or over convex rolls, especially at treeline elevations.

Confidence

Poor - Timing, track, or intensity of incoming weather is uncertain on Friday

Weather Forecast

Wednesday: Freezing Level: 500m Wind: SW, initially moderate increasing to strong by sundown.  5 – 10 expected during the day. Thursday: Freezing Level: 500m Wind: Strong SW backing off of to moderate SW in the evening.  5 - 15 cm expected during the day. Friday: Freezing Level: 500m Wind: Strong S decreasing to light W after dark.  10 -25 cm expected during the day.

Avalanche Summary

Soft slabs up to 25 cm in depth on N aspects around 1400m were reported Monday.  Yet another size 3 avalanche that went to ground was reported Monday on a rocky convexity with a shallow snowpack.  This was in the same area where a wind loaded NE facing slope around 1400m released naturally to ground resulting in a size 3 avalanche on Sunday.

Snowpack Summary

The storm on Friday the 19th left between 20 - 60 cm in it's wake with the Northern portion of the region receiving the most snow along with a significant amount of wind that created large deep hard slabs.  Most of the precip from the last storm fell as rain below 1200m or so which resulted in a crust below treeline.  The region received another 20 cm or so Monday along with some moderate winds from both the west and possibly even east which created soft slabs that were sensitive to skier triggering on Monday.There are a variety of old interfaces now down 40 - 100cm which include facets, crusts and isolated pockets of surface hoar.  There is very limited information about the nature of this interface. I would stress the importance of digging down to find and test weak layers.A strong mid-pack currently overlies a weak base layer of facets/depth hoar. It is worth noting that the snowpack in general is quite shallow compared to averages; triggering the basal weakness may still be possible from thin spots, rocky outcrops or under the weight of larger triggers such as cornice fall.

Régions couvertes