Bollettino valanghe

Purcells

Feb 3, 2019Avalanche Canada
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Archiviato · scaduto 8 years ago

Pericolo valanghe

Mon
Tue
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
Apri la mappa completa

In sintesi

Natural avalanche activity has tapered off to some degree, but human triggered avalanches remain likely. Conservative terrain selection is recommended.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible - Likely
    Dimensione
    1–2.5
    30-80 cm of snow now sits on a weak layer of surface hoar and crust. This layer has been most reactive at lower elevations.

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible - Likely
    Dimensione
    1–2
    Up to 20-55 cm of new snow has fallen in the region and will likely be reactive to human triggers, especially in wind loaded areas.

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    3–4
    The last avalanche observed on the weak facet/crust interface at the ground was on Monday and human triggered avalanches remain possible. Is it a 1 in 100 slope, or a 1 in 1000 slope problem now? We're not sure and this is what makes it so tricky.

Confidence

Moderate -

Weather Forecast

SATURDAY NIGHT - Mainly cloudy with isolated flurries / southerly winds, 10-25 km/h / alpine low temperature near -18SUNDAY - Mainly cloudy with isolated flurries,2-4 cm / southeast winds 10-25 km/h / alpine high temperature near -18MONDAY - A mix of sun and cloud / northeast winds 10 km/h / alpine high temperature near -17TUESDAY - Mainly sunny / northeast winds, 10-15 km/h / alpine high temperature near -13

Avalanche Summary

Avalanche activity continued on Saturday with reports of numerous natural avalanches to size 3.5, as well as explosives triggered avalanches to size 2.5, and human triggered avalanches to size 1.A widespread natural avalanche cycle to size 3 was reported on Friday. There were also several human triggered avalanches to size 1.5 reported in the region on Friday. Some of these reportedly failed on a persistent weak layer that was buried in mid January. This MIN report illustrates how reactive the new snow was on Friday.On Thursday, a few natural and human triggered avalanches to size 1.5 were reported on all aspects around treeline. These also reportedly failed on the persistent weak layer that was buried in mid January.There is a great MIN report from January 22nd that shows a natural avalanche (size 3.5) in International Basin, on the deep persistent layer. Check it out here. While this is an old observation, it is relevant as this layer is still lurking, and may catch people off guard.

Snowpack Summary

20-55 cm of new snow has fallen in the region since Thursday. This new snow sits on wind slab, surface hoar (feathery crystals), facets (sugary snow) and a crust on sun-exposed slopes. A persistent weak layer that was buried in mid January is now buried approximately 30-80 cm. This layer consists primarily of surface hoar, however there is also a crust associated with it on sun-exposed slopes. This layer has been most reactive at treeline and below.The base of the snowpack has a deep persistent weak layer near the ground. This layer consists of facets over a crust. This weak interface continues to produce large and destructive avalanches that are sporadic in nature, and very difficult to predict. This layer is most likely to be triggered from areas where the snowpack is shallow and weak. Rocky alpine bowls, ridge crests and rocky outcroppings are some examples of the kind of terrain to be wary of.

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