Lawinenlagebericht

Lizard-Flathead

Jan 18 – 19, 2021Avalanche Canada
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Archiviert · abgelaufen 6 years ago

Lawinengefahr

Wed
Thu
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

Dig down and investigate deeper layers in the snowpack before committing to big lines.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Hard wind slabs may be stubborn, however slabs will be dense and firm when triggered. Give cornices their space.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely - Possible
    Größe
    2–3

    A weak layer lurks deep in the snowpack. Avalanches on this layer are becoming less likely, however they will be large and destructive if they do happen.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

SUNDAY NIGHT- Cloudy with starry breaks / Moderate northwest wind / Alpine high temperature near -8 

MONDAY - Sunny with patchy cloud / Light northwest wind / Alpine high temperature near -6

TUESDAY - Cloudy with isolated flurries / Increasingly strong southwest wind / Alpine high temperature near -9

WEDNESDAY - Cloudy with isolated flurries / Moderate southwest wind / Alpine high temperature near -7

Avalanche Summary

On Wednesday and Thursday, explosives triggered numerous avalanches up to size 2.5, including a size 2.5 persistent slab avalanche each day.

Overnight Tuesday and during the day Wednesday, a widespread natural avalanche cycle up to size 3 was reported, one of which was a size 2.5 persistent slab avalanche.

Over the past week, there have been several natural and persistent slab avalanches between size 2.5-3 reported in the region. These avalanches are continued reminders of the "low probability; high consequence" scenario that persistent slab problems often create. 

Snowpack Summary

Strong winds have polished and pressed snow into hard slabs and sastrugi, and stripped windward slopes. A melt-freeze crust covers surfaces up to 1800 m. Roughly 80-120 cm of snow is now sitting on (another) crust that extends up to 1900 m, a weak layer of surface hoar may persist in isolated areas at treeline.

The main feature we are monitoring in the snowpack is a layer of weak faceted snow over a hard melt-freeze crust found around 90-200 cm down. Recent sporadic, large, naturally triggered avalanches have occurred on this layer on large alpine slopes and were triggered by either smaller wind slab avalanches, or cornice falls. Weak layers are best managed with conservative terrain selection and careful snowpack analysis. Dig down and investigate the deeper snowpack layers.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Be alert to conditions that change with elevation, aspect and exposure to wind.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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