Avalanche Forecast

Issued: Nov 24th, 2018 4:00PM

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

tim haggarty, Parks Canada

Banff Yoho Kootenay.

Watch for areas where a cohesive slab may exist over the weak, faceted crystals associated with the October 26 crust near the base of the snowpack.

Summary

Weather Forecast

The flow switched back to the west today with light to moderate W or SW winds at the high stations. Temps will remain near -5C at 2000m Sunday but start to climb reaching 0C by Tuesday as a low pressure system approaches from the coast. Precip is possible Sunday and Monday but will intensify for Tuesday as the low reaches the region.

Snowpack Summary

5cm to 10cm of new snow now buries surface hoar, crust on steep south slopes and previous wind effect. With 40 to 85cm at 2200m across the region, the entire snowpack is weakening as it facets. The October 26 crust generally is found 10 to 30 cm above the ground. As this crust breaks down, large facets are growing both above and below it.

Avalanche Summary

Skiers at Harvey Pass near Sunshine Village yesterday remote triggered a slab at about 2500m on a NE aspect while the avalanche control team at Lake Louise triggered a slab on Whitehorn on a similar aspect and elevation. Both of these slabs failed on the October 26 deep persistent layer approx 50 cm deep and were size 1.5- 2.

Confidence

Due to the number of field observations

Problems

Deep Persistent Slabs

Continued, reports of skier remote and explosive triggering of the October 26 facet and crust layer. Avoid areas where a stiffer, or more cohesive slab may exist over these weak, faceted crystals near the base of the snowpack.

If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.Whumpfing is direct evidence of a buried instability.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Nov 25th, 2018 4:00PM