Avalanche Forecast

Issued: Dec 18th, 2017 9:58AM

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

Dan Goodwin, VIAC

Vancouver Island.

Summary

Confidence

Moderate - Variation in precipitation amounts and distribution dependent on location.

Travel/Terrain Advice

Watch for any signs of instability as you travel through the terrain. Cracks, whumpfing or signs of recent avalanches should raise caution. Be especially aware when transitioning into any wind loaded features such as ridge tops and rollovers.

Past Weather

A break in the high pressure ridge that has dominated BC weather since early December has brought a mixing of lower layers of atmosphere and an end to the entrenched temperature inversion. In it's wake, temperatures and freezing levels have dropped to a more seasonal value and a series of Pacific frontal systems has brought light to moderate snowfall to the Vancouver Island mountains above 1300 m. Winds in the range of 15-45 km/h have accompanied these somewhat weak systems.

Avalanche Summary

No new direct observations over the weekend but audible reports in the Mount Cain area with no confirmation.

Snowpack Description

Surface - 5-20 cm of new snow above 1300 m with greater amounts to the north and west of the region have been distributed by light to moderate winds creating loaded pockets up to 50 cm. This new snow appears to be bonding moderately well to the varied old crust surface. Upper - Snow temperatures are beginning to cool and continue to settle and bond to rain crusts that were formed and buried in November. Some sugary snow has been observed around the recent crust that has lingered for the past two weeks. Mid - Well settled. Lower - Well settled.

Weather Forecast

Light to moderate snowfall, cool temperatures and freezing levels to sea level will be the story for the next 72 hrs. It looks as though another ridge of high pressure is building for the coming week bringing more clear skies. Mon - 2-11 cm of snow with higher amounts in central Strathcona Park. Winds west switching to east 15-30 km/h. Freezing levels of 380-1100 m Tue - 2-10 cm of snow with greater amounts in south Strathcona Park. Winds from the north 20-35 km/h. Freezing levels of 0-650 m Wed - No new precipitation. Winds NNW 30-60 km/h. Freezing levels of 0-650 m

Problems

Wind Slabs

Recent and continued snow at alpine and treeline elevations combined with winds from the SE of 15-35 km/h will create wind loaded pockets in the alpine and at treeline ridge tops mostly on NW through E facing slopes. Some natural slab avalanches are possible and will very likely be triggered by a human. These avalanches have the potential to be large (size 2) in size.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Dec 20th, 2017 6:00PM