Avalanche Forecast

Issued: Apr 26th, 2017 4:00PM

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

Ian Jackson, Parks Canada

Banff Yoho Kootenay.

The big hazards right now are cornices and solar warming. These have a good chance of waking up the basal weakness and causing a large avalanche if they happen. Otherwise, watch for sluffing in steeper terrain and enjoy the awesome skiing!

Summary

Weather Forecast

Temperatures will remain cool and winds will remain light for the next three days. We should see 5 - 10 cm on Thursday and a few more centimeters on Friday. A ridge is moving in Friday night and Saturday should see drier and sunnier conditions.

Snowpack Summary

Mondays storm brought 10-20 cm below treeline and 30-40 cm in the alpine with light winds. This sits on melt freeze crusts on solar aspects and below 2500m on polar aspects. A surface crust formed to ~1800m on polar aspects on Wed and higher on solar aspects. The basal weakness has been dormant, but will wake up with solar warming or cornice drops.

Avalanche Summary

Some small loose dry sluffing was observed out of steep terrain during brief periods of sun on Wednesday morning. Otherwise, no new avalanches observed or reported.

Confidence

Timing or intensity of solar radiation is uncertain

Problems

Cornices

Cornices continue to fail. Minimize your time underneath these and remember that a cornice failure could also trigger the deep persistent slab on the basal facets.

Give cornices a wide berth when travelling on or below ridges.Cornices become weak with daytime heating, so travel early on exposed slopes.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Deep Persistent Slabs

The snowpack is gaining strength, but the weak basal facets continue to produce sudden collapse results and can produce large avalanches with large triggers or heat. Stick to planar, supported slopes with a deeper snowpack when entering steep terrain

Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Loose Dry

20 - 40cm of new snow Monday night has had little inputs from wind, sun or warming temperatures at higher elevations. This loose dry snow will sluff easily in steep terrain when the sun comes out or the wind picks up.

Be cautious of sluffing in steep terrain.On steep slopes, pull over periodically or cut into a new line to manage sluffing.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 27th, 2017 4:00PM