Bulletin d’avalanche

Purcells

Jan 31 – Feb 1, 2012Avalanche Canada
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Archivé · expiré 15 years ago

Danger d’avalanche

Thu
Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–5
    New snow and winds blowing from all directions have formed wind slabs on most slopes. You're likely to find the bigger wind slabs on N-E facing aspects but you need to be suspect of all open slopes at and above treeline. Wind slabs are touchy.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    4–7
    Recent avalanche activity indicates that deeply buried weak layers are once again reactive. A skier, sledder or avalanche running in the storm snow could trigger a large avalanche, especially in steep rocky terrain.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–4
    New snow over the weekend developed storm slab instabilities. It may take a few days for the storm snow to settle out. You should remain diligent in both travel techniques and terrain choices. Staying conservative is appropriate.

Confidence

Fair - Freezing levels are uncertain on Friday

Weather Forecast

Tuesday night into Wednesday: Snow amounts near 5cms overnight with 5-10cms during the day. Ridgetop winds switching from the SW to the NW 20-30km/hr. Freezing levels valley bottom. Thursday: High pressure building over the province today will bring dry conditions. Freezing levels will remain valley bottom for most of the day. May elevate in the afternoon. Ridgetop winds will blow from the North 30-40km/hr. Friday: Dry conditions. Warm air and rising freezing levels will persist into Saturday. Ridgetop winds switch, light-moderate values from the SW.

Avalanche Summary

Several size 3 natural slab avalanches were reportedly seen on Monday. These occurred on NE aspects, suspect instabilities could haven been light to moderate loading above treeline producing slab avalanches from specific terrain features. Explosive avalanche control done in the Dogtooth Range produced 2 avalanches up to size 2, running full depth to ground basal facets. These were on NW-N aspects, at 2300m. On Sunday observations include one large size 3.5 slab avalanche that occurred west of Invermere at 2300m on a SE-SW aspect, 600m wide, running 1300m in length, and the slab pulled out to the ground basal layers.

Snowpack Summary

The Purcell's are one of the more complex & variable snow packs in the province right now.The storm over the weekend delivered 20 - 40 cm of snow to the region with moderate gusting strong winds out of the SW, S & a bit of SE. This snow fell on a snow pack that is for the most part, pretty well settled.There are a few exceptions though: The Jan. 13th SH/FC combo has been reactive in ski hill testing, but this needs to be taken with a grain of salt as this snowpack is a bit artificial when compared to a true backcountry uncontrolled snowpack. Regardless, I feel like we can't take our eyes off this layer just yet, remember, it's only two weeks old.It sounds like there is a lot of strong snow over the mid December facet layer which is buried approx. 80 cm on the east side and 200+ cm on the west side. This layer seems to have more energy in the Purcells than any other region in the province and was reactive on Jan. 28th, when a skier remotely triggered a size 3 avalanche. This seem to be a low probability high consequence situation.There are basal facets at the ground which remain a concern, especially on Northerly aspects at high elevations. Snowpack depths at 2000m sit near 2m deep.

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