Phantom Couloir

breemcoll , Tuesday 21st January, 2025 7:15PM

Strong wind gusts and significant snow drifting in the alpine. 10 cm crown refilled in ~10-15 minutes (later in the afternoon). Noticed new sz 1 on east aspect at treeline just above the main mogul run to sherbrooke lake on the way out that we didn't see on the way in. Ski cut sz 1.5 wind slab in the couloir (north alpine aspect as forecasted).

First half of the couloir was a bit of a wallow with some new shallow windslab on top of ~60 cm of 4f-1f snow. In protected areas climbers left in the lower part of the couloir, there was a weak layer under 20 cm of the 4f-1f snow. Occasionally foot penetration went to ground (~110 cm) if you strayed too climbers left in the lower part of the couloir. Snow pack abruptly transitioned in the upper half of the couloir to decently bulletproof windslab at least 50 cm deep (at the very top thinner as overall snow depth decreased). Out of the couloir at treeline, untracked snow was variable and hooky. And of course, the ogden backcountry ski resort moguls on descent to sherbrooke lake.

Lots of wind transport and loading in the alpine. Winds were calm below treeline, gusting between light and moderate at treeline, and gusting strong in the alpine. A few snowflakes landed on me throughout the day, guessing total accumulation to be <2 cm during our time out.

ski cut size 1.5 half way down the couloir just after the snow transitioned from hard deep windslab (nice bootpacking, p-k) to softer snow (some wallowing 1f-4f). Was a bit worried about the transition from on the way up so threw in a ski cut not expecting much as the new softer windslab was averaging <5 cm going up. Pulled down an average 10 cm (deeper lower down) likely due to the winds and transport picking up when we were in the upper half of the couloir. Pulled all the way to end of the couloir. Crown line was filled in within 10-15 minutes. Couldn't see end of the debris field as it quickly drifted in with snow. Could see crown line was approximately 150m down slope of trigger. Also saw a sz 1 at treeline on an east aspect just above the main mogul run down to sherbrooke lake that occurred sometime during the day.