Avalanche Forecast

Issued: Dec 21st, 2017 3:09PM

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

jmcbride, Avalanche Canada

South Coast.

Winds are redistributing the recent storm snow at upper treeline and alpine elevations. Watch for areas of wind-affected "chalky" or "pillowy" snow.

Summary

Confidence

High - The weather pattern is stable

Weather Forecast

FRIDAY: Mix of sun and cloudy, light flurries. Accumulation trace. Ridge wind light from the northwest becoming southwest. Temperature -3. Freezing level 400 m.SATURDAY: Mostly sunny. Ridge wind light from the east. Temperature -4. Freezing level 400 m.SUNDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind light from the southeast becoming south. Temperature -5. Freezing level surface.

Avalanche Summary

On Wednesday a natural Size 2 slab avalanche was reported on a southeast aspect at 1400 m on the North Shore mountains, as well as a Size 1 on a west aspect at 1200 m. Ski cutting however produced no results.On Tuesday a few natural, loose dry avalanches were observed in the recent storm snow. Ski cutting also produced storm slab and loose dry avalanches to Size 1 running far on the December 18th crust. And explosive control work produced storm slab avalanches up to Size 1.5, propagating about 40 m wide with crowns 20-25 cm deep, failing on the December 18th crust.

Snowpack Summary

Northerly winds have redistributed the recent storm snow scouring windward, northwesterly slopes and loading leeward southerly slopes in the alpine and exposed treeline areas. Approximately 20-30 cm of storm snow sits on top of the most recent December 18th melt-freeze crust which formed following Sunday's rain event to upper treeline elevations. Below this crusts lies 20 cm of wet snow which appears to be well bonded to the lower December 16th crust. Below this second crust the snowpack is well settled to ground. Snowpack depths are about 125 cm at 1100 m elevation, with many early season hazards present at lower elevations.

Problems

Wind Slabs

Recent storm snow is now being redistributed by wind at upper treeline and alpine elevations and lies on a widespread melt-freeze crust that has been showing poor signs of bonding.

Watch for signs of instability such as whumpfing, or cracking. Use caution in down wind (lee) areas. Wind loading may create pockets of wind slab.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Loose Dry

Storm snow has been showing signs of poor bonding to the most recent crust. Use caution on steep or convex terrain.

Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 22nd, 2017 2:00PM