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Avalanche Forecast

Archived

Nov 29th, 2022–Nov 30th, 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

North Rockies, McBride, Sugarbowl, Kakwa, McGregor, Pine Pass, Renshaw, Robson, Tumbler.

The north wind and cold continue. Expect the past 80 cm of storm snow to be easily transported. The avalanche danger is heightened in the alpine.

Confidence

Low

Avalanche Summary

Reports from an observation flight on Monday over the Sentinel pass indicate that a past natural storm slab avalanche cycle occurred in steep rocky terrain only. Avalanches in this cycle were up to size 2.5 (very large).

Observation of windslabs naturally triggered have been reported on north aspect terrain between 1350 m and 1450 m, likely occurring on the reported melt-freeze crust.

Please consider sharing your observations via the Mountain Information Network to help us and fellow recreationists.

Snowpack Summary

The storm last week delivered to this region between 40 to 80 cm of new snow. Winds were strong from the southwest during this event, and terrain exposed to this wind has been stripped with new snow building into wind slabs on north aspects.

During the past storm event a period of warming brought rain up to nearly 1500 m and now a melt-freeze crust can be found down 70 cm.

During mid-November, a period of cooling temperatures created a weak layer above the 1200-meter mark and can be found down 80 cm.

Average snowfall depths are around 20 to 60 cm below the treeline and 100 to 120 cm in the alpine.

Weather Summary

Tuesday Night

Low-pressure east of the region will bring light precipitation with greater amounts in the eastern zone. Temperatures are expected to continue to slowly cool as the overarching arctic high is strong.

Cloudy with light flurries, accumulation 1 to 5 cm, 30 to 40 km/h east wind, treeline temperature -25 °C.

Wednesday

Cloudy with light flurries, accumulation 1 to 5 cm, 50 km/h northeast wind, treeline temperature -27 °C.

Thursday

Mostly cloudy with light flurries 1 to 2 cm of snow, 30 km/h northeast wind, treeline temperature -30 °C.

Friday

Mostly cloudy with very light flurries, accumulation 1 cm, 10 km/h northwest wind, treeline temperature -30 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Make observations and assess conditions continually as you travel.

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.