[MCR] bow/peyto

Subject: [MCR] bow/peyto
Date: Sun, 23 Apr 2006 11:12:35 -0600
I was up on the Wapta last Monday to Friday, skiing and climbing between Bow and Peyto.

There is still a wintry snowpack up there. Windslabs linger on the surface and of special note is the late March surface hoar layer now buried 35-85 cm down. Both these layers produced avalanches over the week, the most interesting one being on the headwall above Bow Hut (photos). I'm sure this was on the surface hoar layer, looked like about 50 cm deep, and failing on low angle albeit unsupported terrain. It was triggered by a wind event and morning sun, running at 8.45 am on Tuesday (witnessed by skiers on Bow Lake). This is similar terrain as most other avalanches I saw over the week: upper elevation glacier, N or NE aspect, unsupported terrain.

A profile in the Rhonda/Baker basin at 2900 m showed the surface hoar down 85 cm. There was a windlasb about 20 cm thick on the surface. When I made a column for a compression test it failed and slid on the surface hoar before I cut the back of the column, leaving the 20 cm thick surface windslab hanging suspended! I had never seen that happen before. Another profile on the south ridge of Mt Rhonda showed the surface hoar down 35 cm, beneath a hard windslab.

The obvious question is what the Balfour High Col is like. Over the week at least one party declined to go up there while another safely made it up and over.

Late in the week it was warming and north aspects up to 2400 m had seen a thin crust form. On solar aspects the snow was moist up to ridgetop with numerous loose snow and slab avalanches noted on west aspects, running on a crust about 30 cm down.

All in all a bit of a mixed bag out there. Don't expect any of these instabilities to go away unless there is a significant melt-freeze event that reaches mountain top for at least a couple of days.

Mark Klassen
Mountain Guide
mark@xxxxxxxxxxxx
www.alpinism.com

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