Ross SE Couloir and Area

3cm of new snow overnight at the Loop Brook trailhead. Still a bit low coverage on the approach to the Slot Canyon but nothing too terrible or non-feasible on skis. We broke trail to the Elephant Trunk, i.e. climber’s right of the Bonney Trees without too much difficulties and climbed the SE slopes of Ross. The initially thin and broken cloud cover became widespread and thicker around 10:00. The sun did not poke its head out all day. A quick hand shear on an east aspect at 1600m produced easy results 20cm down on the decomposing Dec 7 SH below the facetted 4-5cm thick temperature crust, thanks to the cold weather of the last few days, so no propagation. No whoomphs of any sort but small isolated 20cm thick slabs could be kicked down without propagation on steep unsupported features, i.e. steep kickturns and pillows (see picture). The top 15cm was sloughing easily and picking up mass on the steeper pieces of terrain. We climbed to just below the Ross SE Couloir where we observed a SZ 2 slightly chunky and crusty debris covered with only 5 cm of new snow. So the feature has most likely slid when the sun came out sometime in the last 72 hours. We transitioned to bootpacking and started climbing. We then heard a loud avalanche on the North Face/Glacier of Bonney, see the avalanche tab. We climbed just over 100m to a little ways above the small ice waterfall and a knife hard supportive unequal icy bed surface was covered with 3-5cm of fresh snow. The skiing looked like it would have been quite rugged and adventurous so we downclimbed below the ice waterfall and skied down. The skiing was fast on the supportive temperature crust 15cm down and many SZ 1 sloughs were triggered requiring some slough management, i.e. either skiing faster than the slough or letting it passed before turning. Fun ski conditions!

At exactly 11:30, a loud avalanche was heard on the North Face of Bonney, not sure at that point if the trigger was a cornice or a serac fall but a long rumble followed. Unfortunately, it was snowing S2 when that happened so we did not have any visual on it. It momentarily stopped snowing shortly afterwards and a crown was just visible below the cliffs of Bonney. A couple areas that had slid down to the bedrock and to the glacier ice could be seen, see picture. So it seems like it was cornice triggered and that the avalanche that ensued was at least a SZ 2.5 but the extent of the debris could not be seen given the very flat light.

Multiple SZ 1 kicked off steep unsupported features, i.e. steep kickturns and pillows. Sliding on Dec 7 broken and rounded SH under a 4-5cm thick facetted/broken down temperature crust. No propagation.