Bollettino valanghe

Lizard-Flathead

Feb 1 – 2, 2021Avalanche Canada
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Archiviato · scaduto 6 years ago

Pericolo valanghe

Wed
Thu
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
Apri la mappa completa

In sintesi

Storm slabs stay touchy at all elevations, especially where the recent snow overlies surface hoar or a crust. Moderate to strong southwest wind continues to form fresh wind slabs on lee terrain features in the alpine and exposed treeline.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2.5

    20-30 cm of recent storm snow has formed reactive storm slabs at all elevations. The new snow slab becomes stiffer with the settlement of the snow and rising temperatures. A failure in the weak layer underneath the slab might propagate wider than expected resulting in larger avalanches. The storm slabs are particularly reactive where they overlie surface hoar in sheltered areas at and below treeline.

    The new snow is redistributed by moderate to strong southwest wind and forms fresh wind slabs on lee terrain features at higher elevations. 

    Cornices are growing larger and becoming more fragile.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

SUNDAY NIGHT: Mainly cloudy, 5 cm new snow, moderate to strong southwest wind, treeline temperature -4 C, freezing level at 1500 m.

MONDAY: Sunny with cloudy periods, 2 cm new snow, moderate southwest wind, treeline temperature -3 C, freezing level at 1800 m.

TUESDAY: Cloudy, 15 cm new snow, moderate southwest wind, treeline temperature -5 C, freezing level at 1500 m.

WEDNESDAY: Cloudy, 15 cm new snow, moderate southwest wind, treeline temperature -8 C, freezing level at valley bottom.

Avalanche Summary

The last few days saw a high amount of avalanche activity with numerous slab avalanches up to size 2 that were triggered by skiers and explosives or released naturally (see this MIN report or this MIN report as an example). A few natural cornice failures were observed on Saturday. Some avalanches were larger than expected (see this valuable MIN post). Several parties reported signs of instability as whumpfing and shooting cracks (this MIN report has illustrative pictures). Loose dry avalanches (sluffs) in steep alpine and treeline features were reported throughout the week. 

Snowpack Summary

20-30 cm recent snow buried surface hoar and other old surfaces. In the alpine, the new snow sits on top of layers of hard wind slab, scoured areas, sastrugi and isolated pockets of soft snow. A hard crust underneath the new snow is found up to 1800 m.    

A solid mid-pack sits above a deeply buried crust and facet layers near the bottom of the snowpack (150-200 cm deep), which are currently unreactive. 

Terrain and Travel

  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Watch your sluff: it may run faster and further than you expect.

Regioni coperte