Avalanche Forecast

Issued: Dec 6th, 2017 4:26PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Loose Wet.

cgarritty, Avalanche Canada

Lizard-Flathead.

A rapid shift to warm, sunny conditions will increase the range of avalanche problems as well as their potential for reactivity.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

Thursday: A mix of sun and cloud with thicker valley cloud due to an alpine temperature inversion. Light west winds. Freezing level to 3300 metres with alpine temperatures of +4. Cooler at lower elevationsFriday: Sunny at highest elevations with valley cloud due to lingering temperature inversion. Light west winds. Freezing level to about 3200 metres with alpine temperatures of +2. Cooler at lower elevations.Saturday: Mainly sunny at highest elevations with continued valley cloud. Light southwest winds. Freezing level to 3300 metres with alpine temperatures of +3. Cooler at lower elevations.

Avalanche Summary

Reports from Tuesday included several observations of wind slabs releasing to Size 2 in the Fernie area. These were mainly triggered with explosives but one Size 1.5 slab did release with skier traffic. Looking forward, forecast sunshine and warm temperatures may have the greatest destabilizing effect where more recent reverse loading and crossloading has occurred at higher elevations. Please submit your observations to the Mountain Information Network (MIN).

Snowpack Summary

Recent shifting winds have been redistributing loose snow at higher elevations, crossloading and forming wind slabs on a wide range of aspects at treeline and above. Below the surface, 40-60 cm of accumulated storm snow now sits above the crust that formed a week ago. The buried crust is supportive and approximately 30 cm thick. It extends from 1600 m to mountain top elevations on all aspects. The bond of our recent storm snow to this crust is expected to be strengthening and it has produced hard, resistant results in recent snowpack tests. Below this interface, the snowpack is moist to ground. The average snowpack depth at treeline is 60-80 cm while a deeper snowpack exists in the alpine.

Problems

Wind Slabs

A recent wind shift from southwest to north means that fresh wind slabs are likely to now exist on a wide range of aspects at higher elevations. Be especially cautious of reverse loaded or cross-loaded slopes that see sun exposure on Thursday.

Be careful with wind loaded areas, especially near ridge crests and roll-overs.Use ridges or ribs to avoid pockets of wind loaded snow.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Loose Wet

Warm, sun-exposed slopes could produce wet loose avalanches either naturally or with rider triggers on Thursday, especially in steeper terrain. This problem will likely be limited to areas above the valley cloud.

Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Dec 7th, 2017 2:00PM