Avalanche Forecast

Issued: Dec 19th, 2014 8:37AM

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

triley, Avalanche Canada

Sea To Sky.

Avalanche danger rising to HIGH as the storm slab continues to develop.

Summary

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

Expect another 10-15 cm of new snow combined with strong Southerly winds overnight. Snow and strong Southwest winds should continue during the day on Saturday resulting in another 15-25 cm by evening. Freezing levels may rise up to about 1500 metres by Saturday evening. Very strong Southwest winds and another 15-25 cm overnight into Sunday morning with freezing levels dropping slightly overnight to about 1100 metres and then rising back up to about 1500 metres on Sunday afternoon as another 5-10 cm of new snow arrives. Yet another pulse of precipitation looks like it will bring 5-10 cm of new snow combined with moderate winds by Monday morning.

Avalanche Summary

No new avalanches have been reported. Expect new storm slab avalanche activity to increase as the storm develops.

Snowpack Summary

A new storm slab is expected to develop above the mix of current surfaces which include a mix of stubborn wind slabs and settled storm snow in the alpine, and a hard rain crust at lower elevations. Surface hoar growth has been reported in sheltered areas. There is still concern for a buried crust/facet layer which formed in November.

Problems

Storm Slabs

The new storm slab is expected to become more likely to trigger or release naturally as the load of new storm increases. Areas at treeline with surface hoar on the recent crust may have wide propagations and fast moving avalanches.

Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.>Give cornices a wide berth when travelling on or below ridges.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Deep Persistent Slabs

The deeply buried weak crust layer from November continues to be a concern. The forecast load of new snow may increase the likelihood of triggering avalanches on this layer. Avoid large un-supported alpine slopes where this crust is present.

Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Dec 20th, 2014 2:00PM