Northern San Juan
AvalancheDanika Gilbert · Dec 27, 2018 · Northern San Juan
Weather
Northern flanks of Red Mountain 2, upper reaches of Corkscrew Gulch from Hwy 550. Skies were mostly clear in the morning with light breeze, colder than previous days temps and clouds and fog rolling in around 1:30pm. Traveled primarily on N to NE aspects, elevations between 10,000' and 11,500'.
Snowpack
On the way up, we had two significant collapses in the zone between 11,000 - 11,300' and found intermittently spatially two ~1cm thick layers underneath the new storm snow (14-20" in previous 48 hrs) or a snowpack entirely of DF and Facets. All locations except those with true southerly exposure (while climbing the ridge) had facets at the ground. Boot pen varied from storm snow deep only on ESE to S exposures to full pen to ground on true N and colder locations.
Avalanche
<TL SS ASu-R4-D2-G On a NNE aspect at ~11,500', occurred on the second ski slope on the standard Midnight ski path. Triggered by second skier as the skier reached the 1/2 point in the slope, fracturing at the top of the path (slow crack) which then released the entire slope, running on the bed surface of large facets on the ground. Full depth of snowpack released, with an average depth of ~100cm across the entire path (~20m wide) and ran into the dense trees below for a total distance of debris at ~90m). Skier 2 was able to ski out of the slide to the west when they heard a call from Skier 3 who noticed the growing crack at the top of the slope (slow release, no noticable collapse). Skier 2 was able to nearly exit the path and post behind a larger tree at the far west end of the path and was minorly impacted by the flank of the debris flow. Skier 1 was further below at a safe location. Party felt that the agreed upon ski/spotting plan and exit routes helped avoid injury or serious incident. All realized prior to skiing that the slope had potential to slide, but matched the upper slopes in characteristics investigated prior to skiing. No noticeable layers were found with quick pole penetration tests, slope appeared to be mostly facets and 30-35 deg. Slope had been skied by a party of 2 skiers prior to the recent storm loads (Tuesday) without incident and old tracks were still visible prior to skiing. Because of concern with the new snow load, the party proceeded cautiously. Inspection after the slide revealed a slightly steeper rollover with on the ground under skier 2's line than the first skiers (<2ft to the east of skier 2's line) due to a rocky spot on the ground. This feature was not evident prior to the avalanche with the snow cover however, which was uniform across the slope at that location. Slope angle was not measured, but estimated between 35-37deg at the rollover itself.