Avalanche Forecast

Issued: Nov 21st, 2017 8:11AM

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

Parks Canada percy woods, Parks Canada

The storm snow continues to settle. Warming temperature will see the avalanche danger increasing.

Summary

Weather Forecast

Rising freezing levels and flurries are forecast for today with light S'ly winds.  Tonight precipitation increases with mod SW winds and rising temperature.  Wednesday the alpine high should reach +2C with wind gust to strong SW and continued precipitation.  Thursday the main storm hit occurs with high winds, warm temps and heavy precipitation. 

Snowpack Summary

The Halloween crust and weak layer continues to form down 100cm in the pack. Sun kissed solar aspects yesterday forming a thin crust. A Saturday profile at treeline at the approach to Bruin's ridge found easy test results 70cm down on surface hoar on thin crust-the Nov 9 interface. Tests at Fidelity at 1900m found mod shear down 43cm on stellars.

Avalanche Summary

Over 30 avalanches size 2-3 recorded in the highway corridor from the 19th and 20th. Most of these slides appeared to be storm snow based with a few releasing down to the Halloween crust. A recent size 2 slide was observed in Cheops North 1 and Frequent Flyer ran size 2 to valley bottom early in the weekend storm.

Confidence

Freezing levels are uncertain on Wednesday

Problems

Storm Slabs

An icon showing Storm Slabs
The weekend storm brought wind and snow in abundance forming a widespread storm slab.  Storm snow instabilities should slowly settle out but warming this afternoon may wake them again.
The new snow will require several days to settle and stabilize.Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
The Halloween crust, while stubborn is active given the right location.  This layer can be found down approx 100cm and is a developing problem.
If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Nov 22nd, 2017 8:00AM