Bollettino valanghe

Sea To Sky

Feb 16 – 17, 2023Avalanche Canada
Vedi sulla mappa
Archiviato · scaduto 4 years ago

Pericolo valanghe

Sat
Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
Apri la mappa completa

In sintesi

Avalanches are possible in wind-loaded areas at treeline and above. Watch for slab properties increasing in wind-affected snow as flurries accumulate throughout the day. Carefully evaluate wind loading as you move through terrain and investigate the bond of wind slabs to the crust below.

Problemi valanghivi

  • Wind Slabs

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

    Southwesterly winds are distributing available snow into fresh wind slabs on north and east slopes in the alpine and upper treeline. Wind slabs may be sitting on a crust making them especially reactive to ridder triggering.

    Previously northerly winds built wind slabs in exposed alpine features. Continue to use caution around these features and watch for areas that have been reverse-loaded and cross-loaded.

  • Persistent Slabs

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

    Two weak layers consisting of a crust with small facets found above them have been reactive to rider traffic in the last week. The first, down 40-100 cm has been reactive at treeline in the Rhododendron and Pemberton Icefields area. The second is found up to 1900 meters and is down 60-150 cm in the snowpack. It has been reactive to human triggering in the Brandywine and Callaghan area on north and west aspect between 1800 and 1600 m. Both of these layers seem like isolated problems at the moment but if triggered they will result in large consequential avalanches.

Confidence

Moderate

Avalanche Summary

On Tuesday, A snowmobiler remote triggered a size 2 persistent avalanche in the Callaghan. The avalanche was reported to be triggered from 10 m away and was adjacent to a heavy traffic area. We suspect this avalanche slid on the mid-January persistent weak layer. See the MIN for details and photos. This is the latest human-triggered avalanche on this persistent weak layer in the region.

For more evidence of this weak layer see this MIN report from last Wednesday when a size 2.5 persistent avalanche was triggered by a rider at Chocolate Bowl. Find another example in this MIN from a skier accidental size 2 persistent slab avalanche that occurred on Saturday.

On Monday afternoon, search and rescue technicians responded to a fatal avalanche incident north of the Sea to Sky region. The avalanche is believed to have occurred on Saturday and was initiated in a shallow rocky area. See the MIN for more details.

Snowpack Summary

10 to 30 cm of snow has been redistributed by variable winds over a variety of surfaces including facets, old wind slabs and a thin breakable crust below 1650 m, in southern and coastal parts of the region. In sheltered areas above 1200 m snow remains dry and unconsolidated.

Two concerning crusts are found in the mid-pack at varying depths throughout the region. A crust from late January is found at all elevations down 40-100 cm with small facets above it. In the Rhododendron and Pemberton Icefield area, this crust has been reactive to rider traffic and in test pits at treeline. In the Brandywine area, a crust found 80-200 cm deep resulted in a few surprisingly large rider-triggered avalanches last week. This layer exists to 1900 m in these areas.

Total snowpack depths are reaching 300 cm in some areas.

Weather Summary

Wednesday Night

Cloudy with isolated flurries, trace accumulation. Winds southwest 15-30 km/h. Treeline temperature -9 °C. Freezing level 400 m.

Thursday

Mainly cloudy with scattered flurries, 5-10 cm accumulation. Winds southwest 20 km/h gusting to 40 km/h. Treeline temperature -8 °C. Freezing level 700 m.

Overnight flurries bring 10-15 cm accumulation.

Friday

Partly cloudy with isolated flurries, trace accumulation. Winds west switching to northwest 20 km/h. Treeline temperature -8 °C. Freezing level 900 m.

Saturday

Partly cloudy with isolated flurries, trace accumulation. Winds northwest 20 km/h gusting 60 km/h. Treeline temperature -6 °C. Freezing level 1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be alert to conditions that change throughout the day.
  • Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.

Regioni coperte