Avalanche Forecast

Issued: Apr 1st, 2018 4:00PM

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

tim haggarty, Parks Canada

Banff Yoho Kootenay.

Some decent propagation in wind loaded start zones on Mt Bosworth during avalanche control today. Winds are shifting to the east as of publishing: new windslabs in some different locations may form for Monday.

Summary

Weather Forecast

A low slipped south of the forecast area pushed by an arctic front over the prairies. 5 cm of snow is expected overnight while winds are shifting to the east and are expected to pick up to the strong range at mountain top as the polar air pushes west bringing a cold night and dry, cloudy day. Expect a return to the SW flow and flurries late Monday.

Snowpack Summary

Friday's storm brought 15-40cm with moderate S and W winds creating wind slabs in the alpine and into exposed areas at treeline. The March 15 suncrust is down 25-50cm on south east through west aspects and has been sensitive to skier triggering over the last few days. The mid- pack land basal layers have been dormant for the past while.

Avalanche Summary

Avalanche control work over the last two days on Mts Bourgeau, Whymper and Bosworth produced avalanches up to sz 2.5. These were limited to the recent storm snow 15 to 50cm deep with wind loading contributing to depths. On Mt Bosworth today, crowns up to 80m wide allowed slabs to entrain enough mass in steep tracks to run 2/3 path.

Confidence

Wind speed and direction is uncertain on Monday

Problems

Wind Slabs

The new snow Friday arrived with strong SW winds and reports vary concerning the extent of the wind effect. Some good propagation was seen in the wind loaded portions of start zones with avalanche control. East winds Monday should redistribute snow.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

This crust has given several groups a surprise over the last while. Be suspicious of solar terrain and recognize that the bond to this crust will vary with subtle changes in slope aspect and angle.

Be cautious with convexities and steep slopes on solar aspects.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2.5

Valid until: Apr 2nd, 2018 4:00PM