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Avalanche Forecast

Archived

Dec 10th, 2021–Dec 11th, 2021

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

Regions

Lizard-Flathead.

Today is a good day to avoid avalanche terrain. Heavy snowfall, wind and warm temperatures are making avalanches very likely.

Snowfall is forecast to be the heaviest in the Lizard Range. If your area sees less than 30cm of snow through the day, reduce hazard to considerable. 

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system. We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

FRIDAY NIGHT: Overcast. 5-15 cm of snow expected. Strong to extreme southwest wind. Temperature rising in the alpine to warmer than -10.

SATURDAY: Overcast. Heavy snowfall. 30-60cm of snow expected through early Sunday morning. Strong to extreme southwest wind. Expect wind speed to increase drastically as you gain elevation. Freezing levels climb to between 1000 and 1500m. 

SUNDAY: Mostly cloudy. 5-10cm of snow expected. Strong southwest wind. Freezing level around 1000m. 

MONDAY: Mostly cloudy. 0-5cm of snow expected. Moderate to strong south to southwest wind. Freezing level back to valley bottom in the morning, rising through the day. Alpine high around -6.

Avalanche Summary

Expect natural and skier triggered avalanches to be likely if the weather forecast holds true.

Yesterday, avalanche control work continued to trigger wind slabs up to size 2.5.

On thursday, natural trigged storm slab avalanches were observed to size 2 near Fernie. Explosives and skiers in the same area also triggered storm slabs to size 2 yesterday, all failing on the melt freeze crust. 

Over the last week natural and skier triggered slab avalanches have been reported in wind loaded features at treeline and above. 

Note there are very few field observations this early in the season. If you venture out into the mountains, please share your observations and/or photos on the Mountain Information Network!

Snowpack Summary

Over the course of the day, 30-60cm of new snow that is falling with strong wind and warming temperatures has the potential to create a reactive, upside-down snowpack. 

Below 2400m, expect to find a thick and supportive melt freeze crust on all aspects down 40-80 cm. 

The snowpack holds several early season crusts about 20-30cm above the ground. Last week's heavy rain saturated the snowpack and has begun to break down this crust at treeline and below, creating a cohesive lower snowpack.

Snowpack depths range from 40-130 cm at treeline elevations. The snowpack tapers quickly below 1800m.

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of a buried crust.
  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • 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.