Avalanche Forecast

Issued: Dec 22nd, 2017 4:34PM

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

Avalanche Canada jmcbride, Avalanche Canada

Winds have redistributed the recent storm snow at upper treeline and alpine elevations. Watch for areas of wind-affected, "pillowy" or hollow drum-like sounding snow.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

SATURDAY: Mostly sunny. Ridge wind light from the northeast. Temperature -6. Freezing level surface.SUNDAY: Mostly cloudy, flurries. Accumulation 5-10 cm. Ridge wind light from the south. Temperature -4. Freezing level surface. Strong outflow winds near coastal valleys.MONDAY: Mostly cloudy, flurries. Accumulation trace. Ridge wind moderate from the northwest. Temperature -3. Freezing level surface.

Avalanche Summary

There were no new reports of avalanche activity on Thursday. However, 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, although ski cutting produced no results. Also on Wednesday evidence of a natural cycle which likely occurred during or immediately after the storm was reported in higher alpine terrain in the northern part of the region. 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 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. A thin sun crust can also be found on solar aspects. Approximately 20-30 cm of storm snow sits on top of the most recent December 18th melt-freeze crust. Below this crusts lies 20 cm of well settled snow above the December 16th crust. Below this second crust the snowpack is well settled to ground. Snowpack depths are about 135 cm at 1100 m elevation, with many early season hazards present at lower elevations.

Problems

Wind Slabs

An icon showing Wind Slabs
Recent storm snow has been redistributed by northerly wind and lies on a widespread melt-freeze crust. More snow and strong outflow winds are expected for Sunday which may build fresh slabs in areas that are not normally loaded by wind.
Use caution in down wind (lee) areas. Wind loading may create pockets of wind slab.Watch for signs of instability such as whumpfing, or shooting cracks.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Dec 23rd, 2017 2:00PM