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Avalanche Forecast

Archived

Jan 29th, 2022–Jan 30th, 2022

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

Regions

North Rockies.

Avalanche danger will increase as new snow and wind form fresh and reactive slabs in leeward terrain features at upper elevations. Wind slabs will be especially touchy where they sit over a crust or surface hoar.

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

Saturday night: Snowfall up to 5 cm. Strong SW wind. Treeline temperature around -5 °C. Freezing level 1000 m.

Sunday: Snowfall 5-10 cm. Strong SW wind. Treeline high around -5 °C. Freezing level 1000 m.

Monday: Snowfall 5-10 cm. Moderate NW wind. Treeline high around -10 °C. Freezing level valley bottom.

Tuesday: Sunny. Light NW wind. Treeline high around -18 °C. Freezing level valley bottom.

Avalanche Summary

The theme over the past week has been wind slab avalanches size 2-3. On Friday, a natural size 2 wind slab was reported on a northeast aspect at 1900 m. Some of the avalanches earlier in the week were failing down to the bedrock in extreme terrain features.

On Friday our field team observed evidence of previous wind slab avalanches having stepped down to deeply buried layers, resulting in large avalanches in Kakwa. This observation has us scratching our heads about the potential for deep avalanches going forward.

Snowpack Summary

New snow and strong wind are forming wind slabs at upper elevations. The new snow falls on highly wind affected surfaces in the alpine, a melt-freeze crust on steep solar aspects and low elevations and a layer of surface hoar in sheltered areas at treeline and below in some areas in the south of the region.

A thin crust may be found 20-30 cm deep, which was the main sliding surface for the wind slab avalanche cycle last weekend. Another crust is found around 70 cm deep but has not shown recent reactivity. The lower snowpack is generally strong and bonded, with one or multiple crusts near the ground. We suspect the lower snowpack could be weak in shallow, rocky, wind-affected slopes east of the divide.

Terrain and Travel

  • Watch for avalanche hazard to increase throughout the day.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • 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.

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.