Avalanche Canada mconlan, Avalanche Canada

South Rockies Avalanche Forecast

Jan 12th, 2018 4:33PM

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.

A Special Public Avalanche Warning is in effect for this region. Widespread, large avalanche activity is possible on touchy buried weak layers. Don't overthink it - maintain very conservative terrain choices and avoid overhead exposure.

Summary

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

SATURDAY: Early morning snowfall, accumulation 1-3 cm, then mostly sunny, moderate northwesterly winds, alpine temperature near -4 C, freezing level near 1000 m.SUNDAY: Mostly sunny with possible valley cloud, light to moderate northwesterly winds, alpine temperature near 0 C, inversion conditions with cold valley air and above-freezing level between about 2000 m and 2500 m.MONDAY: Mostly sunny, light southwesterly winds, alpine temperature near 0 C, freezing level near 2500 m.

Avalanche Summary

The recent 40 cm of snow has been reactive and produced small to large slabs or loose dry avalanches. One release stepped down to the early-season rain crust and facet layer. Storm slabs have most often been observed in direct lee features and steep slopes. Around 1900 m, ongoing reports of touchy conditions have been noted, such as whumpfing and cracking, which is indicative of touchy buried weak layers.

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 easily on this layer, either naturally or with the weight of a person or machine. Forecasted warm air temperatures could increase slab properties of the overlying snow and make this layer 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. New wind slabs can be found in parts of the region due to recent southwest winds. 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

Likely

Expected Size

1 - 2
Recent 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 southwesterly winds.
Use conservative route selection. Choose moderate angled and supported terrain with low consequence.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
Forecasted warm air temperatures could increase the likelihood of triggering buried 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 warming and/or direct sun on starting zones.

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Jan 13th, 2018 2:00PM