Bulletin d’avalanche

Lizard-Flathead

Mar 15 – 16, 2017Avalanche Canada
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Archivé · expiré 10 years ago

Danger d’avalanche

Fri
Sat
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

High freezing levels and continued rain will keep the avalanche danger elevated. The weather forecast is a tricky mix of changing freezing levels and uncertain precipitation amounts.

Problèmes avalancheux

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    1–3
    Cornices are huge and are ripe for triggering with the warm weather. Cornice falls may trigger larger persistent slab avalanches.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    2–3
    Storm slabs are expected to continue to develop at the highest alpine elevations due to forecast new snow and wind. Loose wet avalanches may continue to release at all elevations due to the rain and high freezing levels.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–4
    Storm loading and warming may increase the likelihood of triggering large deep persistent slab avalanches. Concerns include basal facets in alpine terrain and a variety of crust and facet interfaces about a metre deep.

Confidence

Moderate - Freezing levels are uncertain on Thursday

Weather Forecast

Overnight: Freezing level at 2000 metres, slowly dropping by morning to 1200 metres. Expect 15-20 mm of precipitation that will be mostly rain, except at the highest elevations. Thursday: Daytime freezing level around 1500 metres, 5-10 cm of new snow above 1500 metres, moderate southwest winds. Friday: Overnight freezing down to valley bottoms, and then rising back up above 2000 metres. Mostly sunny with valley fog in the morning, and light southwest winds. Saturday: Freezing level remaining above 2000 metres, strong southwest winds, and 5-10 mm of precipitation.

Avalanche Summary

Widespread natural avalanches were reported 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. This avalanche cycle is likely to continue overnight,

Snowpack Summary

Heavy rain to mountain tops has soaked the upper snowpack and caused rapid settlement of the recent storm snow. The surface has been reported to be wet to at least 1800 metres, and moist to 2000 metres or higher. The forecast brief drop in freezing levels in the early morning may not have much effect on the snowpack when the daytime warmth brings the freezing level back up. 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, rapid warming, or strong solar radiation.

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