Bollettino valanghe

North Rockies

Feb 10 – 11, 2022Avalanche 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

Warm temperatures and rain continue to weaken the snowpack. This will increase the likelihood of triggering avalanches on the buried weak layer where present. Uncertainties are best managed with conservative terrain choices.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    The recent snow loaded a weak layer of surface hoar crystals in some areas, which is at a prime depth for human triggering. The layer is most prominent in areas sheltered from the wind at and below treeline. Example terrain features to particularly treat as suspect include the lee side of ridges, openings in trees, cut blocks, and burns. Triggering this layer from a distance away is a concern, watch out for adjacent and overhead slopes.

    The buried weak layer was reported to be present up to treeline in the Torpy Sande and Pine Pass areas and in isolated areas in the Renshaw. Avalanche activity on this layer was reported in the south of the region.

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Overnight Wednesday to Thursday, 10 to 20 cm of new snow is forecast with the higher amounts in the southwest of the region. Expect to find wind slabs in lee terrain features at higher elevations from strong to extreme southwest wind. Storm slabs may be found in sheltered terrain. 

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1–2

    Warm temperatures and rain at lower elevations and the lower alpine will continue to weaken the snowpack. Temperatures will only slowly decrease during the day on Thursday. 

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

WEDNESDAY NIGHT: Cloudy, up to 10 cm new snow in the north and up to 20 cm in the southwest of the region, precipitation will fall as rain at lower elevations and the lower alpine, strong to extreme southwest wind, alpine temperature +1 C, freezing level 2100 m.

THURSDAY: Mostly cloudy with sunny periods, up to 2 cm new snow, strong to extreme west wind, alpine temperature -4 C, freezing level dropping slowly to 1400 m.  

FRIDAY: Mix of sun and cloud, trace of new snow, light to moderate westerly wind, alpine temperature -5 C, freezing level 1300 m.

SATURDAY: Mix of sun and cloud, moderate to strong west wind, alpine temperature -1 C, freezing level 1700 m.

Avalanche Summary

On Tuesday, no new avalanches were reported. 

On Monday, a small skier triggered wind slab avalanche was reported and several slab avalanches released naturally on the buried weak layer. Wet loose avalanches were observed below 1000 m. 

On Sunday, a deep persistent slab avalanche was likely triggered naturally by intense warming and sun and released on depth hoar or the November crust. It occurred just south of the region (see this MIN report). Explosives triggered several large wind slab avalanches up to size 3.

Snowpack Summary

The forecast precipitation Wednesday to Thursday night will fall as rain at lower elevations and the lower alpine and as snow at higher elevations. The snow surface will be moist or wet at lower elevations and likely form a crust when temperatures slowly drop during the day on Thursday. Previous storms brought 50 to 80 cm new snow with the highest amounts in the southwest, less in the north and the least in the east of the divide. The snow formed storm slabs in sheltered areas and wind slabs in lee terrain features from strong south and west wind.

The snow will be particularly touchy where it sits on a weak layer of surface hoar crystals. Reports suggest that the surface hoar is likely most prominent in sheltered openings at and below treeline but could extend into wind-sheltered terrain in the alpine. Example terrain features to treat as suspect include the lee side of protected ridges, openings in the trees, cut blocks, and burns.

The lower snowpack is generally strong and well-bonded. The base of the snowpack is expected to be weak and faceted in shallow, rocky slopes east of the divide.

Terrain and Travel

  • Rain or periods of intense solar radiation can rapidly enhance the effects of warming.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Uncertainty is best managed through conservative terrain choices at this time.

Regioni coperte