Bulletin d’avalanche

Vancouver Island

Jan 13 – 14, 2021VIAC
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Archivé · expiré 6 years ago

Danger d’avalanche

Thu
Fri
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

On Saturday a natural avalanche of unknown size (give the terrain scale it was possibly a size 2) was witnessed occurring on a very steep North aspect slope above foster lake. Additionally in that area, other debris piles from previously natural avalanches where observed. On Monday Mt Washington Avalanche control teams reported a few large (size 2) and numerous small (size 1) natural avalanches that had occurred on North, West and East aspects. Explosive avalanche control triggered produced a few large avalanches and numerous small soft slab avalanches. Explosive triggered avalanches where reported to easily propagate with some of the slab depths up to 100cm.

Problèmes avalancheux

  • Wind Slabs

    • Toutes altitudes
    Probabilité
    Possible
    Taille
    1
    Found on predominantly North aspects, this avalanche problem overlies a variety of surfaces that include below 1500 meters a crust and above this elevation old storm snow. Expect that this problem will still exist, but is beginning to settle and bond with forecast cooling temperatures. **Location:** North aspects and found in both the Alpine and at Tree line specific to terrain just below ridge top. **Possibility:** Triggering of this avalanche problem is possible to likely from light loads such as skiers. Natural avalanches are unlikely to possible. **Size:** If triggered expect these avalanches to be small, and on isolated terrain features large, size 2.

  • Persistent Slabs

    • Toutes altitudes
    Probabilité
    Possible
    Taille
    1
    A layer of facets 20cm thick can be found down nearly a meter in the snowpack. Currently isolated testing of this layer is not producing results. This persistent layer is a concern because when it is trigger consequences will be severe. The likelihood may be low but the consequences are high, continual loading of the snowpack from numerous past storm systems is likely to increase the magnitude and perhaps reach a tipping point where sensitivity to triggering increases. **Location:** Isolated sheltered large terrain features but found on all aspects in both the Alpine and at Tree line. **Possibility of triggering:** Unlikely to Possible to both natural and human triggers. **Size:** If triggered expect these avalanche to be large to very large size 2 to 3.

Past Weather

Past precipitation amounts topped out at 90 mm on the west side of the island with snowfall amounts nearing 45cm on the eastern side. The winds continued moderate from the south west and temps began to rise on Tuesday. Brief periods of clearing and sun presented as well causing surfaces to become moist.

Weather Forecast

A ridge of high pressure to the east of the region is expected to provide a period of cooling and clearing for both Wednesday and Thursday. Beginning late Thursday night a subtropical wave of warm air and moisture, will drive freezing levels to mountain tops 2000 meters and deliver moderate amounts of precipitation in the form of rain. Wednesday: 5-10cm cm, Winds Strong easing to Moderate from the South West, Freezing levels a high of 700 meters.Thursday: Trace amounts, Winds Moderate from the South East, Freezing levels a high of 1000 meters.Friday: 20-30 mm, Winds Strong from the South West, Freezing levels a high of 2100 meters falling to 1200 meters.

Terrain Advice

**Your island bulletin continues to grow, with all the information sharing and increased traffic in the backcountry, it was time. Please review out latest Instagram and Facebook post to review the extensions to your island avalanche bulletin forecast areas. We have expanded our northern boundary to Nimpkish lake reaching to both the west and eastern edges of the island. On the South end we reached down to Lake Cowichan and captured everything in between including 5040 peak, Mount Arrowsmith, Forbidden Plateau, the Beaufort range to name a few**Be cognizant of snow conditions and utilize small slopes to test and investigate the recent storm snow and its reactionary properties.Careful and cautious route finding when transitioning from scoured areas into areas of wind loaded snow.Avoid traveling below and above cornice features as they are large and touchy.Avoid open and steep slopes during periods of warming and rain; even small loose wet avalanches will have enough mass to push a mountain traveler into gullies and over cliffs.

Snowpack Summary

Over the weekend intermittent moderate snowfall and intense wind transport was observed a storm system has delivered significant quantities of snow with extreme winds from the South East. The fact that the South east wind has been so intense will likely create significant loading on North West thru to West aspects, pay particularly close attention to this aspect as it will likely have very touchy wind slabs. Evidence of extreme wind transport of snow to North aspects is at all elevations.Overall snowpack depths have been measured from 200cm to 400cm.A variety of crusts exist in the upper snowpack. Numerous snowpack tests indicate that these crusts are now beginning to bond to the storm snow.The mid snowpack has an unreactive 20cm layer of facets that can be found down 100cm plus. This layer may be isolated to areas that are sheltered and at higher elevations above 1400 meters presents as a melt freeze crust/ poly grain layer.The lower snowpack is dense and very well settled as many reports for island backcountry users and numerous snow profiles have indicated.

Snowpack Details

  • Surface: Wind affected snow scoured on exposed South aspects with deep loading on North aspects. Solar aspects becoming moist 1400 meters and below.
  • Upper: Storm snow and wind slabs from past storms can be found over a crust below 1500 m and over old storm snow above 1500 m.
  • Mid: A 20cm layer of facets can be found down 100cm plus.
  • Lower: Well settled and dense.

Confidence

Moderate - Continued field observations and professional reporting. Increased MIN reports providing a range of good recreational information, much appreciated, please keep them coming.

Régions couvertes