Avalanche Forecast

Issued: Dec 7th, 2017 4:00PM

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

tim haggarty, Parks Canada

Banff Yoho Kootenay.

Be aware that a strong alpine temperature inversion has created warm conditions in alpine start zones. With uncertainty over the October 31 layer lingering: Ice climbers and skiers alike should carefully consider their exposure to overhead terrain.

Summary

Weather Forecast

A ridge of high pressure will continue to dominate the weather through Saturday with clear skies, light winds (although higher in east - west valleys), and a strong alpine temperature inversion. As the inversion established itself Thursday afternoon , temperatures reached 3C at 3000m while 2000m temps only reached -7C.

Snowpack Summary

Suncrusts are developing on steep south slopes with a temperature inversion. Surface hoar up to size 10 has formed. Below 2500m, 30 -50 cm of snow lies over the Nov 27th and Nov 23rd crusts. Both of these now overly the Halloween crust/ facet layer that sits 30-50cm above the ground. This lower layer is a facet layer above 2500m and a crust below.

Avalanche Summary

No avalanches were observed or reported at the time of writing although temperatures have spiked to over 3 degrees C at 3000m due to a strong temperature inversion.

Confidence

Freezing levels are uncertain

Problems

Persistent Slabs

Natural avalanche activity has tapered however, shallow alpine areas warrant caution. Uncertainty around the Oct 31 layer remains especially with the temperature inversion changing conditions at upper elevations. Be wary of warming in start zones.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Be alert to conditions that change with elevation.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Wind Slabs

Recent moderate to strong winds have created variable windslabs in exposed alpine areas along the divide. These may become more sensitive to triggering with warmer temperatures.

Watch for surface cracking and stiffer surface layers of snow. Avoid wind loaded terrain.Use caution in lee areas. Recent wind loading has created wind slabs.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 8th, 2017 4:00PM