Bulletin d’avalanche

Lizard-Flathead

Mar 18 – 19, 2017Avalanche Canada
Voir sur la carte
Archivé · expiré 10 years ago

Danger d’avalanche

Mon
Tue
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
Ouvrir la carte complète

Points saillants

Temperatures may cool, but the snowpack is still warm and the sun will be out in full force on Sunday. There is no reason to expect a rapid drop in avalanche danger.

Problèmes avalancheux

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–3
    Recent warm, stormy weather has seen cornices become huge and ripe for releasing as the sun hits them on Sunday. Cornice falls are an excellent trigger for large persistent slab avalanches.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    2–3
    All the rain that soaked lower elevations fell as snow above about 2000 metres. Expect touchy storm slabs that thicken with elevation in the alpine and be aware that they are an overhead hazard to lower elevations, especially when the sun comes out.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–4
    Be careful not to overestimate the stabilizing effect of cooling temperatures on Sunday. Rain has saturated the snowpack with warmth and deep persistent slabs still have the potential to release naturally or with a sufficient trigger on Sunday.

Confidence

Moderate -

Weather Forecast

Sunday: Sunny. Moderate to strong west winds. Freezing level to 1400 metres with alpine temperatures around -7. Monday: A mix of sun and cloud. Light east winds. Freezing level to 1500 metres with alpine temperatures around -6. Tuesday: Cloudy with isolated flurries and a trace of new snow. Light south winds. Freezing level to 2000 metres with alpine temperatures around 0.

Avalanche Summary

Reports from Friday show a continuation of the recent and ongoing avalanche cycle, with several observations showing explosives triggered persistent slabs (and one storm slab) running from Size 2.5-3. Crown fractures generally ranged from 100-200 cm. On Thursday, storm slabs were observed releasing naturally to Size 2, with explosives control yielding deep persistent slabs to Size 3. Most crown fractures measured about one metre but one impressive storm slab featured a three metre fracture depth. North to northeast aspects were the main performers over both days.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. Looking forward, recently formed storm slabs in the alpine will likely be reactive to human triggering on Sunday. The heightened avalanche activity shown by the above reports should gradually decrease as cooling temperatures begin to penetrate the snowpack.

Snowpack Summary

Stormy weather on Saturday has been forming storm slabs at high alpine elevations while rain continues to saturate the snowpack at treeline and below. Below the new snow accumulations, recent heavy rain to mountain tops 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. This crust will deteriorate at all elevations where rain is occurring before gradually reforming as temperatures cool again on Saturday night. 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 and storm slab avalanches.

Régions couvertes