Avalanche Forecast
Purcells
A weak layer is buried at a depth prime to human triggering. As the overlying snow gains slab properties, destructive avalanches will likely result. Cautious route finding is advised, particularly at treeline elevations.
Avalanche Problem 1: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Use conservative route selection. Choose moderate-angled and well-supported terrain.
- Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.
Avalanche Summary
Small loose avalanches have been noted from steep, sun-exposed terrain the past days.
Numerous signs of deeper instability have been noted in the snowpack over the past week, including whumpfing and cracking between 1700 and 2100 m, and two skier-triggered avalanches suspected to have released on the December 15 weak layer. Expect the potential to trigger persistent slabs to increase as the snow continues to settle into a cohesive slab.
Snowpack Summary
A warming trend is creating a dangerous slab above buried weak layers in some areas. Numerous persistent weak layers exist in the snowpack. Dry snow overlies two layers composed of weak and feathery surface hoar, with the deeper layer (December 15) buried 40 to 80 cm. This layer is found most often around and below treeline but has been reported as high as 2400 m. As the overlying dry snow becomes more cohesive and forms a slab, this layer has the potential to create easily-triggerable destructive slab avalanches. Where and when this will occur is tricky to predict and even professionals are scratching their heads about it. It is a good time for conservative decision-making.
The snow surface is variable, consisting of dry snow on shaded aspects, a sun crust on steep solar aspects, and wind effect in exposed alpine and treeline locations.
Deeper in the snowpack at depths of about 70 to 110 cm, a rain crust from November is producing variable snowpack test results, from sudden fracture characters to no result. This layer is considered dormant for now, but could be triggered where the snowpack is thin.
Please share your recent observations through the Mountain Information Network.
Weather Forecast
SATURDAY: Cloudy with light snowfall, accumulation 2-5 cm, light to moderate southwesterly winds, freezing level near 900 m.
SUNDAY: Cloudy with light snowfall, accumulation 1-3 cm, light southwesterly winds, freezing level near valley bottom.
MONDAY: Cloudy with light snowfall, accumulation 1-3 cm, light southwesterly winds, freezing level near valley bottom.
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Around 40 to 80 cm of snow sits above a touchy weak layer. As this snow settles and gains slab properties, a dangerous slab that is easily triggered will likely form.