Avalanche Canada mconlan, Avalanche Canada

South Rockies Avalanche Forecast

Jan 10th, 2018 5:10PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs and Persistent Slabs.

The snowpack is creating tricky avalanche conditions, with new snow falling on buried weak layers that are showing signs of instability.  Cautious route finding is advised.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

THURSDAY: Cloudy with snowfall, accumulation 10-20 cm, light to moderate southwesterly winds, alpine temperature near -12 C, freezing level below valley bottom.FRIDAY: Partly cloudy, light to moderate westerly winds, alpine temperature near -9 C, freezing level below valley bottom.SATURDAY: Partly cloudy with intermittent snowfall, moderate to strong westerly winds, alpine temperature near -8 C, freezing level near 1200 m with possible inversion conditions.

Avalanche Summary

The new 20 cm of storm has been reactive and produced small storm slabs. This has most often been observed in direct lee features as well as below treeline elevations. Around 1900 m, ongoing reports of touchy conditions have been noted, such as whumpfing and cracking.

Snowpack Summary

An unstable weak layer from mid-December (predominantly feathery surface hoar crystals and/or a sun crust) is found at treeline and below treeline elevations. Slabs can fail very easily on this layer, either naturally or with the weight of a person or machine. Forecasted new snow will continue to stress this layer and likely make it easier to trigger.The snowpack is variable across the region, but persistent slabs are generally a widespread problem. Wind slab and storm slab distribution will be more variable. Hard wind slabs can be found in parts of the region due to recent extreme southwest winds but more recently northerly winds, which have reverse-loaded some slopes. This means that wind slabs may be found on every aspect. Windward alpine slopes may be scoured; and variable wind slabs are found at treeline and alpine elevations. New snow is likely to fail as storm slabs and/or loose avalanches. Deeper in the snowpack, an early-season rain crust and sugary facets exist. An avalanche in motion could step down to these deeper layers, creating a large and destructive avalanche. Overall snowpack depths are variable across the region. It is generally shallower in the east.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Very Likely - Likely

Expected Size

1 - 2
New snow is likely to fail as loose snow or slab avalanches, especially in steep alpine and treeline terrain or open slopes below treeline. Snow may be deeper in lee features due to strong winds.
Use conservative route selection. Choose moderate angled and supported terrain with low consequence.Back off if you encounter whumpfing, hollow sounds, or shooting cracks.Use caution when entering lee areas. Recent wind loading may have created wind slabs.

Aspects:

All aspects.

Elevations:

All elevations.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Likely - Possible

Expected Size

1 - 3
New snow may overload touchy weak layers. The trees may not be the safe haven you expect: adopt a cautious attitude to all avalanche terrain.
Avoid open slopes and convex rolls where buried weak layers may be preserved.Back off if you encounter whumpfing, hollow sounds, or shooting cracks.Minimize overhead exposure during periods of heavy loading from new snow and wind-transported snow.

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Jan 11th, 2018 2:00PM