Bulletin d’avalanche

Coquihalla

Mar 19 – 20, 2023Avalanche Canada
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Archivé · expiré 4 years ago

Danger d’avalanche

Tue
Wed
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

Warm spring daytime temperatures are here - watch for surface snow turning wet and be wary of cornices and overhead hazards.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–3

    There are several crusts in the mid-snowpack. Their depth ranges from 50-150+ cm and most likely found in thin snowpack areas or reloaded bed surfaces. A large trigger, such as a cornice fall or a smaller avalanche in motion, could trigger a very large avalanche on one of these deeply buried weak layers.

    Glide slabs are unpredictable and may release during the warming.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    The snowpack is slowly recovering and cooling from the recent sun and warm temperatures. A weak pulse could drop up to 10 mm wet precipitation, this load could further destabilize an already dynamic snowpack prolonging the wet avalanche hazard. Where dry snow prevails (at the highest elevations), pockets of stubborn wind slab may lurk on lee slopes.

Confidence

Moderate

Avalanche Summary

On Friday and Saturday, loose wet avalanches to size 2.5 were observed on East to Southwest aspects. Glide slabs have been opening and running to size 2.5 in regular/common locations.

On Tuesday, a natural size 2 wind slab and size 3 glide slab were reported both around 1300 -1500 m. A skier-triggered storm slab was also reported on Zoa. The slab was a size 1.5 and was triggered near the top of the slope with no involvement. It was 40 cm deep and slid clean on the underlying old snow surface. Check out the MIN HERE. Thanks for the report and happy to hear everyone was ok.

A natural persistent slab size 3 was reported on Tuesday but it's suspected that it failed Monday during the storm. This avalanche happened on a shady aspect at 1800 m, with the failure plane unknown but suspect an early March interface.

Snowpack Summary

Daytime warming or wet flurries will promote moist snow surfaces, continuing to destabilize the upper snowpack. Cornices loom over ridgelines and may become weak during periods of solar radiation or warming.

A moist surface/sun crust has formed on all aspects up to 1800 m and solar aspects into the alpine. Last week's 40 cm of snow covered a variety of old snow surfaces, including a sun crust on solar aspects, a melt-freeze crust at lower elevations and a spotty surface hoar in sheltered locations. The storm snow was most reactive on southerly slopes 1500-1800 m, sitting on an old sun crust.

Additionally, several crusts in the mid/lower snowpack. Their depth ranges from 150 to 250 cm. The mid and lower pack is generally settled and bonded in thicker snowpack areas, with a lingering concern for these deeper buried interfaces in shallower snowpack areas.

Weather Summary

Sunday night

Starry sky with increasing clouds. Southeast wind 10-20 km/hr. Treeline low temperature -4 C. Freezing level 1400 m.

Sunday

Unsettled and cloudy, light wet flurries during the day, 5 mm. Southeast wind 15-25 km/hr. Treeline high temperature +2 C. Freezing level 1600 m.

Tuesday

Light wet flurries transitioning to sunny breaks. Light northeast wind. Treeline high temperature +3 C. Freezing level 1500 m.

Wednesday

Sunny and calm. Light northerly wind. Treeline high temperature +2 C. Freezing level 1600 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
  • Wind slabs may be poorly bonded to the underlying crust.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Rain or periods of intense solar radiation can rapidly enhance the effects of warming.

Régions couvertes