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Avalanche Forecast

Archived

Dec 10th, 2021–Dec 11th, 2021

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

Regions

South Rockies.

Today is a good day to choose mellow slopes that are protected from the wind. Time will tell how well the new snow bonds to the crust and wind slabs that it covered. 

Confidence

Moderate - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

FRIDAY NIGHT: Mostly cloudy. Trace of snow expected. Moderate to strong southwest wind. Could be extreme west winds in alpine. Temperatures rising from alpine low of -12.

SATURDAY: Overcast. 10-15cm of snow expected and another 5-15 cm possible overnight. Freezing levels climb to between 1000 and 1500m. Strong to extreme southwest winds, likely to increase drastically as you travel to higher elevations. 

SUNDAY: Mostly cloudy. 5cm of snow expected. Moderate to strong southwest winds. Alpine high around -7.

MONDAY: Partly cloudy. 0-10 cm of snow expected. Light south winds at treeline and strong southwest in the alpine. 

Avalanche Summary

No new avalanches observed. Expect human triggered avalanches to become likely as the storm snow accumulates.

Explosive control work earlier this week produced multiple wind slabs to size 1.5, running on the most recent melt freeze crust. 

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, 15-25 cm of new snow that is falling with strong wind and warming temperatures has the potential to create a reactive, upside-down snowpack. 

The new snow is falling on an extremely variable surface. Before this storm, strong to extreme westerly winds stripped exposed terrain in the treeline and alpine, to the thick and smooth melt freeze crust or to rock. In sheltered features, the wind has redistributed snow into wind loaded pockets of over 50cm. 

The snowpack holds several early season crusts about 20-40cm above the ground below 2300m. 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 30-110 cm at treeline elevations. The snowpack tapers quickly below 1900m.

Terrain and Travel

  • Watch for fresh storm slabs building throughout the day.
  • Closely monitor how the new snow is bonding to the crust.
  • Be aware of highly variable recent wind loading patterns.

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.