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Avalanche Forecast

Archived

Dec 21st, 2023–Dec 22nd, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
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, Sugarbowl, Kakwa, McGregor, Pine Pass.

Choose conservative terrain and give the storm snow time to bond.

Fresh snow and increasing winds are further burying a concerning layer of surface hoar.

Confidence

Moderate

Avalanche Summary

Poor visibility has limited observations. We have received reports of debris from large avalanches in run outs at lower elevations. Likely storm slabs starting in the alpine.

If you go out in the backcountry, please consider sharing your observations on the Mountain Information Network (MIN).

Snowpack Summary

Up to 30 cm of new dense snow has buried a variety of previously wind-affected surfaces.

A concerning surface hoar layer is roughly 40 to 70 cm below the surface.

The mid snowpack likely contains multiple frozen crusts, while the lower snowpack is generally faceted. Average snowpack depths at treeline range from 50 to 100 cm.

Weather Summary

Thursday Night

Cloudy with up to 15 cm of new snow expected, southwest alpine wind 50 to 80 km/h, freezing level around 2000 m.

Friday

Mostly cloudy with around 5 cm of new snow expected, southwest alpine wind decreasing to 30 to 60 km/h, freezing level falling to valley bottom.

Saturday

Clearing throughout the day with trace amounts of new snow expected, west alpine wind 20 to 40 km/h, treeline temperature -7 °C.

Sunday

Mostly cloudy with no new snow expected, southwest alpine wind 40 to 70 km/h, freezing level rising to 1700 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • Choose conservative terrain and watch for clues of instability.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.

Problems

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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.