Avalanche Forecast

Issued: Mar 23rd, 2017 4:00PM

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

Ian Jackson, Parks Canada

Banff Yoho Kootenay.

Natural activity is starting to taper, but given the historic nature of the last cycle, forecasters have no confidence in the current snowpack. Any slope that hasn't slid is suspect!

Summary

Weather Forecast

Southwest flow continues with flurries expected on Friday night, possible accumulations of 5-8 cm by Saturday. The temperatures will fall overnight Thursday, but expect freezing levels to reach about 1600 meters and treeline temperature from -5 to -8. Winds will remain moderate from the southwest.

Snowpack Summary

100cm of dense, rounded snow comprises the upper half of the snowpack and sits on a very weak base of depth hoar. This unstable structure produces consistent, sudden collapse test results in the depth hoar layer approximately 60cm from ground. Two shears persist near the surface down 15 and 35cm indicating lingering instability in the storm snow.

Avalanche Summary

Although the natural activity is tapering, we are still getting reports of large avalanches daily. This morning, a size 2.5 was triggered by solar radiation on a NE aspect of Jimmy Junior near Bow Summit

Confidence

Due to the number of field observations

Problems

Deep Persistent Slabs

Natural activity is starting to taper, but the snowpack is still very weak. Most days this week, we have seen large avalanches running to valley bottom on this layer. Don't expose yourself to any avalanche terrain that hasn't recently avalanched.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.Be aware of the potential for wide propagations due to the presence of hard windslabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 4

Wind Slabs

Wind loading was occurring through the day on Thursday, and fresh windslabs have formed at higher elevations. These windslabs are easy to trigger and will likely be enough load to trigger a larger avalanche.

If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

2 - 3

Valid until: Mar 24th, 2017 4:00PM