[MCR] Rockies: Twin Cairns / Sunshine slack country

Spent the final day of the ACC Calgary AST2 going up Twin Cairns and skiing conservative terrain in the Sunshine slack country. Relevant observations:

Snowpack – variable 100 to 140cm deep and major wind damage. Whumpfing and cracking on the low angle terrain approaching the backside. Hollow like a drum in many areas up high. Ski penetration was 0 to 20cm. Foot penetration was variable but up to 60cm. The back side of Twin Cairns was wind-hammered sastrugi. The cornice along the ridge crest had built a bit since last week. Did a compression test on a nearly flat feature a few hundered meters outside the ski area boundary and got a moderate sudden planar (pop) result on the 11th tap down 20cm on 2mm stellar crystals (1 finger soft slab). Then got a sudden collapse (drop) on the 17th tap down 70cm on 1 to 2mm facets. Identical results on a second test.

Avalanches - Several size 1 to 3 natural avalanches in steep alpine terrain seen from the summit. Some failed near ridge crest; some just below rocky features. All on E and SE aspects. Notable is what appeared to be a size 3 in the Healey Creek slide path. Also notable is a size 2 and a size 1 that likely occurred during the storm on E facing lines that are sometimes skied off Twin Cairns. Crowns on the latter two now becoming obscured due to additional wind transport.

Weather – cool temperatures with variable sun and cloud with light to moderate winds all day. Not a lot of wind transport today as most of the snow had already been moved in the previous wind event.

Terrain Use – skied mellow terrain up to 25 degrees both up and down. Avoided overhead hazard. Ski quality poor to very poor on windward side and fair to good where sheltered or slight lee.

Cyril Shokoples MG
ACC AST2 Crew