Bulletin d’avalanche

South Coast

Mar 7 – 8, 2021Avalanche Canada
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Archivé · expiré 6 years ago

Danger d’avalanche

Tue
Wed
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

New snow and wind will elevate the avalanche danger. Triggering avalanches at upper elevations is likely, especially in wind-drifted areas. Continue to make conservative terrain choices and steer clear of cornices while the storm snow settles and stabilizes. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–2.5

    Strong south winds have had ample snow to drift into reactive wind slabs on lee features at upper elevations. Watch for cracking, changes in snow stiffness, and the pattern of wind-drifting in the terrain where you are traveling. These wind slabs are likely and have the potential to be large. The combination of wind and snow may be loading cornices to their breaking point, which can trigger avalanches on slopes below. 

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–2.5

    Variability in snowfall amounts and freezing levels over the weekend has complicated the distribution of storm slab problems in the region. Dial back terrain choices anywhere you find more than 20 cm of new snow.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

A parade of storms continues through the weekend

Saturday night: Overcast, 5-15 cm of snow, strong south winds, freezing level near 700 m. 

Sunday: Mainly cloudy, 10-20 cm of snow, moderate to strong southwest winds, freezing level near 800 m. 

Monday: Clearing skies, isolated morning flurries with up to 5 cm of snow, light southeast winds, freezing level rising to 1300 m by end of day.

Tuesday: Mainly sunny, light southeast winds, freezing level rising to 1400 m. 

Avalanche Summary

Slabs in the new snow are expected to be touchy at upper elevations, where snow and wind have created conditions that are primed for triggering. 

Cornices may reach their breaking point. See this MIN for an example from Sky Pilot last Sunday.

Snowpack Summary

Another 15-25 cm of snow is forecast to accumulate by midday on Sunday above 800 m. Above 1300 m, this will add to the previous 25-40 cm of snow that blanketed slopes on Friday. Below 1300 m, new accumulations will fall on top of a warm crust or wet snow surfaces. The recent snow has been accompanied by moderate to strong strong south winds, forming touchier slabs on leeward slopes. Pay attention to how wind has redistributed snow and investigate the bond of the new and old snow interfaces as you travel in the backcountry on Sunday. Massive cornices exist on ridgelines, which can act as triggers on slopes below. 

Freezing levels remained elevated throughout Friday's storm, saturating the snowpack below 1300 m. A cooling trend over the weekend is expected to settle and strengthen the snowpack below this widespread March 5th rain crust. 

Terrain and Travel

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Cornice failure may trigger large avalanches.

Régions couvertes