Mt Wilson - close call

Jasper National Park

ruari.macfarlane , Friday 5th April, 2019 8:55PM

Wilson peak via south colouir/gully and east glacier. Close call, see last paragraphs. Couloir is full of wet avalanche debris, great freeze overnight (crampons helpful) softening to moist surface in PM and becoming unsupportive in undisturbed snow, but was still wasier to walk down half the couloir than to ski. 220-280cm snowpack low on the glacier, but sags and open crevasses visible in a number of spots, all elevations. Good cold powder on alpine north aspects, 15cm recent storm snow, 10cm ski pen (but 5cm on east aslects, slight crust). Small surface windslabs in immediate lees, 2 natural size 1s seen near summit (steep E lee), a few small whumphs in immediate lee features. 3 old, quite deep persistent slabs visible, size 2-2.5 on steep north and NE aspects above 2750m had us avoiding any steep terrain on the glacier. Generally the snow under the fresh was wind affected and very supportive, impossible to get a pole through, but we had one large whumph on flat glacier at 2700m, where the snow appearance and terrain was the same as everywhere else, but the stucture was very different for 15m of thahe skintrack: 45cm of unsupportive slab over a thick layer of super soft (fist-), striated facets. We guessed this persistent problem was isolated to more sheltered areas where the overlying slab is thin and soft, but it seemed odd. Then, we had a serious close call re-ascending the 200m, steep N facing slope back to the col at end of the day. We had skiied it (skiiers right, see photo) in the morning, finding only immediate lee windslab over supportive, hard old snow. Skinning back up, skiiers left to right mid height, suddenly encountered another small area (4m long) of same hollow structure , once again visually indentical to the rest of the slope. Took one step too many, and a huge whumph was heard running right up the middle of the slope to the top (though wasnt heard by the 2nd skiier on one side of the slope). 2 ski guides, both surprised, and very thankful this 38 degree slope didn't release. On this slope we had thought small windslab was the only problem we were dealing with - wrong. Although ski conditions are nice on N aspects, The persistent slab in the Sask crossing area demands serious consideration at the moment. We also observed one fresh persistent slab (natural), sz 2.5 on an East alpine slope, north of the columbia icefields. Initiated in the middle of 40+ degree slope below rocks. Thanks

Snow conditions were: Crusty, Wind affected, Powder. Weather conditions were: Warm, Cloudy. We rode: Alpine slopes, Mellow slopes, Steep slopes. Riding quality was ok.

Avalache Conditions: Whumpfing or drum-like sounds or shooting cracks.

Location

52.01285985 -116.78068126

Mt Wilson - close call

Source: Avalanche Canada MIN