Lawinenlagebericht

South Rockies

Mar 12 – 13, 2021Avalanche Canada
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Archiviert · abgelaufen 6 years ago

Lawinengefahr

Sun
Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Buried weak layers remain possible to be triggered, where they still exist. Rising temperatures and solar input may increase the reactivity of these layers. Be alert to conditions that change with sun exposure. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1.5–2.5

    Two persistent weak layers exist in the snowpack that could be triggered by riders:

    • The upper layer is buried 30 to 60 cm and primarily consists of weak faceted grains.
    • The deeper layer is buried 60 to 100 cm and consists of surface hoar, faceted grains, and/or a hard crust.

    The most likely areas to trigger these layers is where a hard wind slab exists above the layers and where the snowpack is not capped by a thick melt-freeze crust. Rising temperatures and solar input may increase the reactivity of these two layers. 

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

THURSDAY NIGHT: Mostly clear, 30 km/h west wind, alpine low -12 C, freezing level at valley bottom.

FRIDAY: Mostly sunny, 20 km/h west wind, alpine high +1 C, freezing level rising to 2000 m.

SATURDAY: Sunny, calm wind, alpine high +6 C, freezing level 2500 m.

SUNDAY: Mostly sunny, 10 km/h south wind, alpine high +6 C, freezing level 2700 m.

Avalanche Summary

No new avalanches were reported for the area on Wednesday or Thursday.

Snowpack Summary

A dusting of snow overlies a thick melt-freeze crust in many areas, with the exception being on north aspects above around 1700 m. Old wind slabs may exist on northerly aspects at alpine and treeline elevations, whereas windward slopes have been scoured to rocks or a hard crust. On solar aspects and below the freezing level, the snow may moisten during the heat of the day. Cornices may also weaken over the day.

Around 30 to 60 cm of snow sits above a persistent weak layer of sugary faceted grains that was buried in mid-February. There have been a handful of avalanches that released on this layer in the past few weeks. There is another persistent weak layer that was buried at the end of January, found around 50 to 80 cm deep. This layer consists of feathery surface hoar, facets, and/or a hard melt-freeze crust. Periodic avalanches continue to be triggered on these layers by riders, particularly where a stiff wind slab sits above them. Check out this MIN that shows the positioning of the layers in the snowpack near Crowsnest Pass.

Weak faceted snow and a decomposing melt-freeze crust can be found near the base of the snowpack. 

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Cornices become weak with daytime heating or solar exposure.
  • Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.

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