Lawinenlagebericht

Lizard-Flathead

Dec 10 – 11, 2020Avalanche Canada
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Archiviert · abgelaufen 6 years ago

Lawinengefahr

Sat
Sun
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

The recent snow is not sticking well to the crust and storm slabs will likely be reactive to human triggers at upper elevations on Thursday. 

Lawinenprobleme

  • Storm Slabs

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

    The new storm snow is not bonding well to the recent crust. Storm slabs may continue to be reactive to human triggering and loose dry avalanches may occur from steep terrain features. Southwest winds may have formed deeper deposits on lee aspects building new and reactive wind slabs in the alpine and in "alpine-like" features near treeline, particularly where these slabs sit on top of a crust.

Confidence

Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region. Uncertainty is due to limitations in the field data.

Weather Forecast

High pressure will build off the coast today bringing dry and cooler conditions through the forecast period.

Thursday/ Friday: Mix of sun and cloud. Alpine temperatures near -5 with freezing levels falling to the valley. Ridgetop wind light from the East.

Saturday: Sunshine with some cloud. Alpine temperatures near -10 and ridgetop wind light from the southwest.

Avalanche Summary

On Wednesday, the new storm snow saw a poor bond to the underlying crust. Natural and human triggered avalanches were widespread and up to size 2 at treeline and above. Limited propagation was reported, however; these avalanches were running far and fast down the path as the snow slid on the crust. This storm slab may continue to be reactive to human triggers on Thursday and if the sun comes out loose dry sluffing from steep terrain features may be seen.

Have you been out? If so, we would love to hear about it on the Mountain Information Network. A picture is worth a thousand words! Thanks for your submissions. 

Snowpack Summary

10-20 cm of new snow fell at upper elevations while the rest of the precipitation came in as rain or freezing rain. Reports suggest that the freezing rain occurred from 1900m to 2100m “ish” with rain at lower elevations which likely destroyed most surface hoar. I also suspect very little surface hoar survived at higher elevations between the wind and the warming/sunshine last weekend, but maybe wind-sheltered pockets still exist? A reactive storm slab does exist, especially where the new snow sits above this recent rain/freezing rain crust. Isolated pockets of wind slab may be reactive on leeward slopes where the new snow deposits into deeper drifts. 

Digging deeper in the snowpack two predominant crusts exist from November. A widespread rain crust from early November that can be found up to 2500 m and buried down around 100 cm and a shallower one from late November down around 30 cm. These crusts have shown no recent reactivity in snowpack testing and this “potentially” problematic snowpack structure is not currently listed as an avalanche problem but remains on our radar moving forward. The snowpack is thin and variable in wind-scoured areas, and it tapers rapidly at lower elevations. Snowpack depths at sheltered upper treeline elevations are 70-90 cm and still below threshold below treeline.

Terrain and Travel

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Closely monitor how the new snow is bonding to the old surface.
  • Be alert to conditions that change with elevation.
  • A crust on the surface will help bind the snow together, but may make for tough travel conditions.

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