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Avalanche Forecast

Archived

Dec 18th, 2021–Dec 19th, 2021

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

Regions

Lizard-Flathead.

Heavy snowfall and strong winds over the past 24 hours have created dangerous avalanche conditions. It's a great day to head to the ski resort and give the snowpack time to adjust to a large amount of new load.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

Saturday Overnight: Snowing, heavy at times with another 15-30cm of accumulation. Strong southwest winds will ease to light and shift to the west by the morning. Freezing levels dropping to valley bottom with alpine temperatures around -10 C.

Sunday: Partially cloudy with isolated flurries in the wake of the front. Light westerly winds with alpine temperatures around -12 C. 

Monday: Mainly cloudy with flurries, trace to 5cm of accumulation. Winds increasing throughout the day, moderate to strong west winds at ridgetop by end of day. Alpine temperatures around -10 C.

Tuesday: Partially cloudy with moderate to strong westerly ridgetop winds and light flurries. Alpine temperatures around -10 C.

Avalanche Summary

On Saturday, operators reported numerous size 1-2 loose dry and storm slab avalanches.

On Friday, operators reported several size 2.5 natural and cornice triggered storm slab in the alpine. Numerous explosives' and ski cutting results both loose dry and storm slab where observed up to size 2. 

On Friday, several natural slab avalanches where reported in the backcountry adjacent to Fernie Alpine Resort, with one notable persistent slab failing on the early December crust.

Snowpack Summary

An intense storm came through the region yesterday, bringing 40-60 cm of new snow. Storm slabs are expected to be widespread across aspects and elevations. In exposed areas in the alpine and treeline, strong southwest winds will have created deeper deposits in lee areas. 

Below this new snow, consolidated snow from the previous weekend storm sits over a substantial crust that formed in early December. This crust is likely 20 cm thick (or more) and is present across aspects below 2400m. A thin layer of weak facets (sugary snow) can found above this crust. 

The lower snowpack consists of a mix of various early season crusts and mainly moist snow. Snowpack depths range from 55-170 cm at treeline elevations and taper quickly below 1800 m.

Terrain and Travel

  • Stick to simple terrain and be aware of what is above you at all times.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Problems

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.

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.