Bulletin d’avalanche

Northwest Coastal

Feb 27 – 28, 2015Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

Sun
Mon
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

A moist snow surface is an indicator that the warm and sunny conditions are weakening the snowpack. Avoid steep sun exposed slopes during the afternoon.Are you a member of Avalanche Canada? Join today at avalanche.ca/membership

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2
    Strong outflow winds have caused reverse loading and thin wind slab formation. Use extra caution as you transition into wind affected terrain.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–3
    Warming and solar radiation will destabilize the upper snowpack on steep sun-exposed slopes during the afternoon.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    3–5
    This is a low probability problem with large consequences. A weak basal layer resulted in several full depth avalanches during the last sunny period which could be repeated this weekend. Avoid steep, sun exposed slopes during the afternoon.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

A ridge of high pressure is the dominate feature for the next three days resulting in dry and sunny conditions. On Saturday, there is some model uncertainty regarding freezing levels which could reach as high as 2000m in parts of the region but will more likely be around 1500m. This warm air coupled with sunny conditions could make it feel unusually warm in the alpine for February. Temperature inversions are possible and it may be cooler in the valleys. Alpine winds on Saturday are forecast to be moderate-to-strong from the NW switching to NE. On Sunday, warm air conditions are again possible at higher elevations. Alpine winds are forecast to remain moderate-to-strong from the N-NW. On Monday, freezing levels are forecast to return to normal and be 500-800m. Strong outflow winds are expected for Monday.

Avalanche Summary

On Thursday, several size 1 skier initiated avalanches were reported.  It is expected that these were thin wind slabs. Last week several full-depth avalanches up to Size 3 were observed on all but North aspects. If the region gets substantial warming and sun on Saturday, isolated events like these could once again become active.  Loose sluffs from steep sun exposed slopes are also possible.

Snowpack Summary

A dusting of new snow has buried the previously variable snow surface which may have included wind-pressed surfaces or old wind slabs, a sun crust or old rain crust, surface hoar, and/or surface facets. A layer of surface hoar buried in the upper snowpack has been reported in some areas and is worth investigating before committing to any big alpine terrain. At the base of the snowpack, weak facets may be persisting.

Régions couvertes