Bulletin d’avalanche

Lizard-Flathead

Mar 17 – 18, 2017Avalanche Canada
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Archivé · expiré 10 years ago

Danger d’avalanche

Sun
Mon
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
4 · Fort
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Points saillants

Saturday's weather puts all the ingredients in place for a natural avalanche cycle to generate large, destructive avalanches. Extreme caution is required for any travel in avalanche terrain.

Problèmes avalancheux

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–3
    Cornices are huge and are ripe for releasing after sustained warm temperatures. Cornice falls are an excellent trigger for large persistent slab avalanches.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    2–3
    A potentially heavy snowfall will combine with intense winds to form touchy new storm slabs at high elevations on Saturday. Rain may fall as high as 1800 metres and promote loose wet avalanches. Both problems have the potential to trigger deep slabs.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    2–4
    The lack of an overnight refreeze will make the impact of Saturday's 2200m freezing levels even stronger. Warming aside, new snow, wind, and rain are set to provide ample natural triggers for deep persistent slabs.

Confidence

Moderate -

Weather Forecast

Friday night: Wet flurries bringing approximately 10 cm of new snow to higher elevations. Rain below about 1700 metres. Strong to extreme southwest winds. Saturday: Periods of snow and rain bringing 15-30cm of new snow to higher elevations. Rain below about 1800 metres. Strong to extreme southwest winds. Freezing level to 2200 metres with alpine temperatures of 0 to +1. Sunday: Sunny with cloudy periods. Moderate west winds. Freezing level to 1500 metres with alpine temperatures around -6. Monday: A mix of sun and cloud Light southeast winds. Freezing level to 1700 metres with alpine temperatures around -5.

Avalanche Summary

Reports from Thursday show a continuation of the recent avalanche cycle, with storm slabs releasing naturally to Size 2 and explosives controlled deep persistent slabs to Size 3. North to northeast aspects have been the most active. Most crown fractures have measured about one metre but one impressive storm slab featured a three metre fracture depth.Reports from Wednesday showed widespread natural avalanches up to Size 3.0. Most of these were reported to be loose wet avalanches gouging and entraining mass as they travelled down the path. The heightened avalanche activity shown by the above reports should be expected to persist on Saturday.

Snowpack Summary

5-10 cm of new snow fell over Thursday night. Below it, recent heavy rain to mountain tops has soaked the upper snowpack and caused rapid settlement of our recent storm snow. Below freezing temperatures since the rain event have refrozen the wet snow into a crust, which has been reported to be supportive above about 1700 metres. The existence of this crust may not have much of a stabilizing effect on the snowpack, especially as freezing levels rise again on Friday through Saturday. Isolated basal facets still exist in shallow snowpack areas and can produce destructive full-depth avalanches. Possible triggers for these deeper weak layers include cornice falls, sustained warming, or storm slab avalanches.

Régions couvertes