Purcells Avalanche Forecast

Issued: Feb 8th, 2021 4:00PM

Tue Feb 9th Current Conditions
Alpine Moderate Treeline Moderate Below Treeline Moderate
Wed Feb 10th 2 Day Outlook
Alpine Moderate Treeline Moderate Below Treeline Moderate
Thu Feb 11th 3 Day Outlook
Alpine Moderate Treeline Moderate Below Treeline Low

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs and Persistent Slabs.

Triggering avalanches may be possible in specific wind-drifted features or in isolated open glades near treeline where a buried weak layer persists. Monitor for these conditions where you travel. 

Summary

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

Brrrrrr! Cold and dry conditions persist under arctic air

Monday night: Mostly clear, light northwest wind, alpine temperature -24 C.

Tuesday: Clear, light northwest wind, alpine high temperature -20 C.

Wednesday: Mainly sunny, light northeast wind, alpine high temperature -22 C.

Thursday: Mainly sunny, light northeast wind, alpine high temperature -25 C.

Avalanche Summary

Over the weekend, small (size 1-1.5) loose dry avalanches in unconsolidated snow were reported in steep terrain. Operators along the southwestern border of the region with higher snow totals reported natural and remote-triggered activity in the recent snow. These avalanches were small to large (size 1.5-3) breaking 60-100 cm deep and occurred on south aspects above 2300 m. 

On Sunday, there was also a report of a small (size 1) explosive-triggered avalanche breaking on a weak layer of surface hoar. Last week, a skier remotely triggered a size 2.5 persistent slab avalanche from a ridgetop near Quartz Creek, which also failed on the surface hoar. 

Snowpack Summary

Up to 15 cm of low density snow over the past several days has combined with strong northwest winds to create wind slabs which may be possible to human trigger in specific lee features. In sheltered areas, cohesion-less powder may be prone to dry loose avalanches that can run far and fast in these cold, dry conditions. With clear skies, there is uncertainty as to how much direct sun on Tuesday might warm steep slopes midday given the frigid temperatures.

50-80 cm of snow from the past week is settling over a very weak layer of surface hoar. Recent avalanches on this layer have primarily been reported at treeline and "treeline-like" features below treeline in the northern half of the region. Although the likelihood of triggering these avalanches is decreasing, this weak layer warrants assessment in open, sheltered slopes at treeline where this layer is likely pronounced and preserved. 

Down 60-100 cm, an older layer surface hoar and/or a thin melt crust from mid January can be found. This layer was more prominent in the north of the region in sheltered, open slopes at treeline.

Deep persistent weak layers can still be found in the lower snowpack. These weak layers are most likely to be triggered from rocky areas with a shallow or thin to thick snowpack.

Terrain and Travel

  • Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
  • Stay off recently wind loaded slopes until they have had a chance to stabilize.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Unlikely-Possible

Expected Size

1.5 - 2.5

Previous strong winds have redistributed recent low density snow into wind slabs on lee features at upper elevations that may be possible to human trigger. 

Aspects:

North, North East, East, South East, South.

Elevations:

Alpine, Treeline.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Unlikely-Possible

Expected Size

1.5 - 2.5

A weak layer of surface hoar is buried 50-80cm on sheltered slopes near and below treeline. Activity appears to be slowing on this layer, though it may be possible to trigger in isolated areas. 

Aspects:

All aspects.

Elevations:

Treeline, Below Treeline.

Valid until: Feb 9th, 2021 4:00PM

Forecast Trend

The latest forecast danger ratings, broken down to elevation. See how an elevation is trending.