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Avalanche Forecast

Archived

Jan 28th, 2022–Jan 29th, 2022

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Northwest Inland.

Keep an eye on the wind. Thin but touchy wind slabs are likely to form throughout the day. Sensitivity to triggering these slabs will be greatest where they have formed over surface hoar.

Confidence

High -

Weather Forecast

Friday night: Stormy weather with up to 5cm of snow throughout the day. Moderate to strong south winds and a low of -6 at 1600m.

SATURDAY: Stormy weather continues with another 5-10cm of snow and moderate to strong wind from the southwest. Freezing level rising to 1000m.

Sunday: some light flurries with light west winds. High of -4 at 1600m.

Monday: some light flurries with moderate west winds. High of -4 at 1600m.

Avalanche Summary

two natural cornice triggered avalanches up to size 3 were observed over the past few days on southeast aspects at treeline.

Earlier in the week there were several large machine triggered avalanches on persistent weak layers throughout the region. 

Snowpack Summary

As the storm builds on Friday and Saturday new wind slab will form over a variety of surfaces including facets, surface hoar and old wind slab. The new snow will not bond well to these surfaces. In the southern part of the region it is possible to find a rain crust up to 1500m.

Below this we have two persistent weak layers, the first is a surface hoar layer from mid January buried down approximately 30cm. The second is a layer of facets from early January which is now down 50 to 80cm, it has been most reactive where wind slab has formed above it and will now likely require a large load to trigger.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
  • Wind slabs are most reactive during their formation.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.