Bollettino valanghe

South Columbia

Apr 15 – 16, 2021Avalanche Canada
Vedi sulla mappa
Archiviato · scaduto 5 years ago

Pericolo valanghe

Sat
Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
Apri la mappa completa

In sintesi

With no overnight refreeze the solar radiation and warm temperatures will continue to weaken the snowpack and cornices. Avoid exposure to sun exposed slopes and cornices, especially in the afternoon. 

Check out the latest Forecaster's Blog on warming and how to stay safe.

Problemi valanghivi

  • Cornices

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely - Very Likely
    Dimensione
    2–3

    Cornices are large and fragile. Warm temperatures and sun exposure will lead to cornice falls. Many natural cornice failures were reported recently. Cornice falls are dangerous on their own and they can trigger slabs on slopes below. 

    Cornices often break further back than expected. Give them a wide berth when travelling on ridgetops. Avoid slopes with cornices overhead, especially if they are exposed to the sun and during the heat of the day. Take into account long runout distances when travelling underneath slopes with cornices overhead.

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1.5–3

    Surface snow can quickly lose cohesion and become unstable with strong solar radiation and warm temperatures. Freezing levels are forecast to stay at 2600 m overnight. Clear skies during the night might allow for a shallow refreeze but the snow will likely become moist/wet in the early morning hours. 

    Back off slopes when the snow becomes moist or wet. Avalanches might grow larger than expected by entraining snow along the way and reach lower elevations. Avoid exposing yourself to slopes that are exposed to the sun, especially in the afternoon. Be aware what is above you when leaving your skiing or riding area.

Confidence

High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

A ridge of high pressure continues to bring sunny and dry weather with freezing levels around 3000 m even at night. On Sunday the ridge is forecast to break down bringing light precipitation and lowering freezing levels.

Thursday night: Clear, moderate northeast wind, alpine low +1 C, freezing level 2600 m.

Friday: Sunny, moderate northeast wind, alpine high +8 C, freezing level 2800 m. 

Saturday: Sunny, moderate northwest wind, alpine high +12 C, freezing level 3000 m.

Sunday: Mainly cloudy with isolated flurries, trace of new snow, moderate northeast wind, alpine high +8 C, freezing level lowering to 2100 m.

Avalanche Summary

Numerous wet loose avalanches to size 2 and one size 3 were observed on steep solar aspects on Thursday. A few small wet loose avalanches in steep rocky terrain were reported on Tuesday as well as a small slab avalanche triggered by a skier on a northeast facing alpine slope. Wind slabs were reactive last weekend, several natural and ski cut size 1-1.5 and a few size 2 were observed on Saturday and Sunday. 

A couple of recent natural cornice failures size 2.5 did not trigger slabs on slopes below except for one which triggered small slab avalanches.

Neighbouring Glacier National Park reported a few very large (size 3-4) glide slab releases last Thursday. Glide slabs are hard to predict and can release at any time, so it is important to avoid slopes with glide cracks.

Snowpack Summary

The snow surface consists of a melt-freeze crust on solar aspects and shaded aspects up to treeline which transitions into moist/wet snow during the day. Dry snow can still be found on northerly aspects in the alpine. 20-40 cm of recent snow has formed isolated pockets of wind slab on leeward slopes and behind terrain features. The recent snow sits on a series of melt-freeze crusts on all aspects below 1900 m and southerly aspects to mountain top. Reports indicate the snow is bonding well at these interfaces. On North aspects in the alpine, the recent snow sits on dry wintery snow surfaces and possibly surface hoar on wind-sheltered slopes. 

Cornices are large, fragile and failing with warm temperatures. Several natural cornice falls were observed recently. 

The recent warm weather is expected to have helped old persistent weak layers heal, including a few crusts buried over the last month as well as a facet layer 150 cm deep from the mid-February cold snap. However, with each day of warm weather the likelihood of persistent slab avalanches increases slightly. 

Terrain and Travel

  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Avoid sun exposed slopes, especially if snow surface is moist or wet.
  • Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.

Regioni coperte