Avalanche Forecast

Issued: Dec 10th, 2016 3:23PM

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

Avalanche Canada rbuhler, Avalanche Canada

Continued heavy snowfall is expected to create widespread reactive storm slabs. Very conservative terrain selection is critical and travel in avalanche terrain is not recommended.

Summary

Confidence

Moderate - Due to the number of field observations on Saturday

Weather Forecast

Snowfall is expected to continue Saturday overnight and into Sunday. Weather models are currently showing the potential for another 30-50cm of snowfall by the end of the storm. On Sunday, freezing levels are expected to be at around 500-700m and alpine winds are forecast to be moderate from the southwest. On Monday, dry conditions are expected with a mix of sun and cloud. Freezing levels are forecast to fall back down to around sea level and alpine winds should be light from the northwest. Sunny, dry, and cold conditions are currently expected for Tuesday.

Avalanche Summary

On Friday, a size 1.5 skier triggered avalanche was reported on the MIN.  The slab was 20-30cm thick and the avalanche was 30-40m wide.  By the end of the storm on Sunday, parts of the region could see storm slabs 60-80cm thick. These slabs are expected to be reactive to human triggering, especially in wind loaded terrain. Natural avalanches are expected during periods of heavy snowfall.

Snowpack Summary

As of Saturday afternoon parts of the region have seen 40-60cm of new snowfall, with a lot more expected by Sunday afternoon. The new snow is falling on a variable surface that includes settled snow on southerly aspects, loose snow on shaded aspects, isolated pockets of surface hoar, and sun crusts on steep solar aspects. Overall the incoming snow will likely bond poorly to this interface. The thickest and most touchy storm slabs can be expected on north-facing wind-loaded features. An old rain crust was down 30-50 cm prior to the storm, and reports had suggested that the snow above it was poorly bonded to the crust on some shady north aspects. Below the crust, the snowpack is settled and strong.

Problems

Storm Slabs

An icon showing Storm Slabs
Heavy snowfall has created touchy storm slabs. In many areas, the storm snow likely sits over a weak layer, which will make the storm slabs very reactive to human triggers.  Natural avalanches are expected during periods of heavy snowfall.
Avoid avalanche terrain during periods of heavy loading from new snow and wind.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

2 - 3

Valid until: Dec 11th, 2016 2:00PM