Bulletin d’avalanche

Sea To Sky

Mar 28 – 29, 2016Avalanche Canada
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Archivé · expiré 11 years ago

Danger d’avalanche

Wed
Thu
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

Substantial warming and sun exposure on Tuesday will destabilize the upper snowpack. Extra caution is required around and below cornices, in recently wind loaded areas, and on steep sun exposed slopes.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–4
    Wind slabs should be expected in immediate leeward features on all aspects in exposed terrain.  Wind loading was from the south over the weekend but switched to north on Monday causing reverse loading. 

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–5
    Large cornices are expected to get weak with warming and sun exposure, and natural cornice releases are possible in the afternoon.  They can be destructive by themselves, and may also become the trigger for a slab avalanche on the slope below.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–3
    Loose wet sluffing is expected on sun exposed slopes during the heat of the afternoon.  Rising freezing levels may increase the size and run length of natural sluffing. 

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

A blocking ridge of high pressure is the dominant feature for the week. Dry and clear conditions are expected for Tuesday through Thursday. Freezing levels are expected to climb to as high as 3000m on Tuesday afternoon and should be above 3000m on both Wednesday and Thursday afternoon, with cooling during the overnight periods. Strong outflow winds are expected on Tuesday in exposed terrain. Light to moderate outflow winds are forecast for Wednesday and Thursday is forecast to be calm.

Avalanche Summary

On Sunday, a natural size 1 storm slab was reported from a north aspect 40 degree slope at 2000m elevation. Skiers were triggering size 1 soft slabs in wind loaded northeast aspect slopes at 1900-2000m. Explosives triggered storm slabs up to size 2. On Saturday, a natural cornice failure triggered a size 2 storm slab on a northeast aspect at 2000m. Another natural cornice failure triggered a size 2.5 storm slab on a northwest aspect at 2100m. Explosives also triggered several size 2 cornice releases. One of these cornice releases triggered a 15-40cm thick storm slab on the slope below. Loose wet sluffing was also reported on steep south facing slopes. As things heat up on Tuesday, natural cornice releases and solar triggered sluffing are both expected. Cornices have the potential to trigger lingering storm slabs on the slopes below, especially on north aspects. Wet slabs may be possible on steep south facing terrain.

Snowpack Summary

Up to 15cm of new snow accumulated over the weekend in sheltered areas. Over the weekend, southerly winds were loading north aspect leeward slopes. However, outflow winds on Monday are reported to be loading south aspects in the alpine while exposed north aspect slopes are being wind pressed and scoured. Large cornices are lingering and are expected to become very weak this week. Below the surface problems, the mid snowpack is generally well-settled throughout with no notable persistent weaknesses. On Monday, a sun crust is expected to have formed on south aspects. Melt-freeze conditions are expected to be widespread this week with very high freezing levels.

Régions couvertes