Bulletin d’avalanche

Northwest Coastal

Dec 8 – 9, 2017Avalanche Canada
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Archivé · expiré 9 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

The incoming storm is expected to deliver more snow (and greater avalanche danger) to coastal areas. Expect new snow to bond poorly with the surface.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2
    Fresh storm slabs will begin to build as a storm pulse brings moderate snowfall with strong winds. Poor bonding is expected at the surface, so slabs will likely be very touchy. Expect thicker, more dangerous slabs in coastal areas and on lee aspects.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2
    Light rain and and wet flurries on Saturday may cause small loose wet avalanches to occur, mainly in steep terrain and where rain or moist new snow accumulates.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–3
    Weak layers buried near the base of the snowpack can't be dismissed while new snow and wind load the surface. Releasing a thick storm slab or wind slab in the right location may provide enough of a trigger to step down a deep early season weakness.

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Saturday: Cloudy with flurries bringing 5-15 cm of new snow to higher elevations, increasing overnight. Light rain possible below 1000 metres. Greatest accumulations in coastal areas. Strong to extreme south winds. Freezing level dropping from about 1800 to 1400 metres over the day with alpine temperatures around 0 to -1.Sunday: Continuing wet flurries bringing approximately 10 cm of new snow to the high alpine. Light rain below about 1900 metres. Moderate to strong south winds. Freezing level to 2400 metres with alpine temperatures around +1.Monday: Mainly sunny. Strong south winds. Freezing level to 3200 metres with alpine temperatures of +5

Avalanche Summary

Warm alpine temperatures and sunshine initiated numerous wet loose avalanches to Size 1.5 on steep solar aspects in the alpine around the Terrace area on Friday. Natural slab avalanches icefall releases reached to Size 2.5 in the Bear Pass area. Looking forward, expect new snow accumulations to bond poorly with the crust and surface hoar that form our current snow surface. New snow loading may also begin to overload the December 4 surface hoar layer (now down about 15 cm), where it exists. Please submit your observations to the Mountain Information Network. (MIN)

Snowpack Summary

Snowpack depths in the region remain below seasonal, with recent heavy wind effect creating variable depths of around 110 to 190 cm at treeline elevations in the Shames area. Solar and temperature crusts now exist on the majority of the the surface and surface hoar was observed developing on sheltered aspects above the valley cloud in the Bear Pass area on Thursday. Another layer of large surface hoar that was recently observed in the Shames area is now buried about 15 cm below the surface. Information on the distribution and reactivity of this layer is limited. Below it, storm snow received last week is gradually settling above a 5-10 cm thick crust (November 23) down roughly 70-100cm. Another layer of surface hoar (November 11) continues to be observed down approximately 140 cm in the Bear Pass area, showing some signs of improved bonding. The widespread crust/facet interface that was buried at the end of October can now be found 90-160 cm deep. Below it, the basal snowpack is a mix of weaker, sugary snow.

Régions couvertes