Bulletin d’avalanche

Kootenay Boundary

Mar 3 – 4, 2022Avalanche Canada
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Archivé · expiré 5 years ago

Danger d’avalanche

Sat
Sun
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

Stability is gradually improving but riding quality may not be! 

There is still uncertainty surrounding reactivity of storm slabs in the alpine. Test the bond of new snow on smaller features with low consequences before committing to bigger lines. 

Problèmes avalancheux

  • Persistent Slabs

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

    Persistent weak layers could be potential problems under the recent load of new snow.

    Weak layers from February (mostly crusts and surface hoar) are likely down around 60 cm and may become more reactive as the overlying snow has formed a thicker and more cohesive slab. Two weak layers of surface hoar from January are likely down around a meter and were primarily a concern in the east of the region on northerly aspects around treeline. 

    Storm slab and loose wet avalanches have the potential to step down to these deeper layers. 

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2.5

    Though stability is improving, human triggering of storm slabs should remain on your radar. 

    Test the bond of new snow on smaller terrain features with low consequences as you travel through various elevation bands and aspects.

    Cornices have grown during the last system as well so give them a wide berth.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

Wednesday night: Light snowfall trace to 5 cm, light southwest wind, freezing levels around 1500 m, treeline temps around -1.

Thursday: Light flurries possible 0-5 cm, wind light and variable, freezing levels between 1500-1700 m during the day, treeline highs of +2.

Friday: Light flurries overnight trace to 5 cm easing by the morning, freezing levels dropping to valley bottom overnight. Mostly sunny during the day, light northeast wind, treeline highs around +4.

Saturday: Sunny, no new snow, light northeast wind, good overnight refreeze but temperatures will rise during the day to +2.

Avalanche Summary

On Wednesday storm slabs were still reactive (up to size 2) to small explosives. On Tuesday explosives control triggered large slab avalanches in the size 2-3 range. Although visibility was poor a widespread cycle of natural storm slabs in the size 2-2.5 range was also evident. There was a remote triggered size 1.5 avalanche reported in the east of the region as well. Some loose wet activity and pinwheeling was also reported at lower elevations.

On Monday there were various reports of natural and rider-triggered avalanches in the size 1-2 range, some with surprising propagation.

Snowpack Summary

Some places in the Kootenay boundary have received over 60 mm of water from this system. That has translated to about 20-60 cm (depending on elevation) of heavy, upside-down type snow. Depending on overnight refreeze, you may find a melt-freeze crust on the surface up to 1900 m. All of this new load sits on top of sun crusts on south-facing terrain, freezing rain crusts, old wind-pressed snow, and even some feathery surface hoar crystals in some locations. Moderate to strong southwest winds have likely contributed to cornice growth and some wind loading as well.

Weak layers from mid-February and late January made up of crusts and/or surface hoar crystals can be found around 60-70 cm deep. There are not a lot of recent avalanches on these layers, but they are still on the radar of operators in the area.

Terrain and Travel

  • Use small low consequence slopes to test the bond of the new snow.
  • Be alert to conditions that change with elevation.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Régions couvertes