Avalanche Forecast

Issued: Nov 30th, 2016 3:50PM

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

Avalanche Canada triley, Avalanche Canada

Some thin wind slabs continue to be reactive at higher elevations. Expect avalanche danger to increase on Friday when the new storm arrives.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Friday

Weather Forecast

Flurries and unsettled conditions continuing overnight and Thursday morning with freezing levels remaining around 1000 metres combined with light northwest winds. Winds increasing to strong from the southwest on Friday with 15-20 cm of new snow above 1500 metres. The freezing level should rise to 1500 metres at the beginning of the storm and then lower as a trailing cold front moves across the region from the northwest. Saturday should be overcast with another 3-5 cm of new snow combined with moderate to strong westerly winds.

Avalanche Summary

Thin soft slab avalanches size 1.0 continue to be reported in the Whistler area on Tuesday. Some reports from Monday of skier controlled soft slab avalanches up to size 1.5 where the surface snow has slabbed up above a less dense (one finger over fist) layer of recent storm snow.

Snowpack Summary

We have a few reports of a new surface hoar layer that may have been buried on Tuesday night (Nov 29th). Areas with this layer may develop a reactive storm slab on Friday when the new storm is forecast to arrive. Soft slabs about 20 cm deep have been reported from the Spearhead Glacier area on Tuesday. It sounds like these are most reactive where they are sitting on old wind blasted surfaces. Watch for shallow wind affected areas that may not gain strength as quickly as deeper well settled snowpack areas. Snow depths increased rapidly last week bringing treeline snow depths to about 200 cm. Much of this recent storm snow has settled and gained significant strength. That said, the last burst of wind and snow on Saturday and Sunday created reactive soft storm slabs which appeared to be especially touchy in higher, wind-exposed terrain.

Problems

Wind Slabs

An icon showing Wind Slabs
Thin wind slabs have developed in the lee of southerly winds. These wind slabs have been reported to be reactive where they are sitting on old wind scoured surfaces and in shallow snowpack areas.
Be alert to conditions that change with elevation.Be cautious as you transition into wind affected terrain.Stay off recent wind loaded areas until the slope has had a chance to stabilize.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
The early November crust is now buried between 30-200 cm deep. The bond between the crust and the storm slab from last week is variable. Avoid convex slopes where the storm slab may be able to propagate wide and deep fractures above the crust.
Use caution in areas where the old surface crust was polished by the winds before it was buried.Use caution on open slopes with convex rolls that may propagate long avalanche fractures.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Dec 1st, 2016 2:00PM