Bollettino valanghe

Northwest Coastal

Jan 26 – 27, 2020Avalanche Canada
Vedi sulla mappa
Archiviato · scaduto 7 years ago

Pericolo valanghe

Tue
Wed
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
Apri la mappa completa

In sintesi

Triggering avalanches remains likely where strong winds have drifted the recent snow into slabs at higher elevations. Stay alert and monitor for these conditions if travelling in these areas.

Problemi valanghivi

  • Wind Slabs

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

    Strong southwest winds continue to drift new snow into slabs on lee features in the alpine and exposed ridges near treeline. While natural avalanche activity has tapered, human triggering may still be possible on Sunday. East of Terrace, a chance of step-down to lower layers exists, increasing the potential size for that part of the region. The wind slab problem overlaps with areas where cornices are also a concern. 

Confidence

Moderate - Uncertainty is due to rapidly fluctuating freezing levels.

Weather Forecast

Saturday night: Cloudy, scattered flurries with 2-5 cm of snow possible, strong south winds, alpine temperature -2 C, freezing level around 1000 m.

Sunday: Cloudy, 2-5 cm new snow, 10-15 cm near Kitimat, strong south winds, alpine high temperature -2 C, freezing level around 800 m.

Monday: Mostly cloudy, 10-15 cm near Terrace, 20-30 cm near Kitimat, moderate southwest winds, alpine high temperature -3 C, freezing level around 500 m.

Tuesday: Mix of sun and cloud, light south wind, alpine high temperature -5 C, freezing level around 200 m.

Avalanche Summary

Over the past 48 hours, numerous natural loose wet avalanches in steep terrain up to size 2 were observed up to 1000 m. Small pockets of human-triggered wind slab were reported at treeline elevations closer to Terrace, while larger (size 2-3.5) wind slabs were reported further north in the Bear Pass area releasing naturally from alpine start zones.

Reports of deep persistent slab avalanches have been trickling in throughout the month, with the last reported event occurring on Jan 17th. They are associated with a November crust layer near the base of the snowpack which has produced very large avalanches (size 3+) with crown depths of around 2 m. These have typically run in alpine terrain, on lee or cross-loaded slopes. Recent loading has been a good test for this layer and it seems to be trending less reactive.

Snowpack Summary

Around 1 m of recent storm snow is settling rapidly. A rapid warm-up moistened snow surfaces up to 1400 m, which was described as "a thigh-burning, elephant snot mix of coastal pow-tatoes" in this MIN report. 

In exposed areas above 1400 m, strong southerly winds are building wind slabs on north facing slopes. The new snow rests on extensively wind affected surfaces at upper elevations and a thick layer of weak facets in sheltered areas near treeline and below.

A crust from mid November lurks at the base of the snowpack. The last reported avalanche on this layer was Jan 17th, and it will most likely require a large trigger such as explosives or cornice fall to initiate this deep persistent slab problem.

Terrain and Travel

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Expect slab conditions to change drastically as you move into wind exposed terrain.
  • Stay off recently wind loaded slopes until they have had a chance to stabilize.

Regioni coperte