Vail & Summit County
AvalancheAnonymous · May 23, 2017 · Vail & Summit County
Weather
On Northstar Mountain/Hoosier Pass, rolling fog and clouds from sunrise becoming mostly sunny around noon. A fairly strong, consistent northwesterly wind blew most of the morning especially along the ridge line of Northstar Mountain (~13,300). Snow plumes were evident blowing off the east ridge of Quandary, especially near the summit. 3-6" of snow fell last night and significant transport occurred by the time we were on the trail at 6:15 am.
Snowpack
We dug a pit at ~13,050 on a 40 degree SE slope, a similar aspect to the Cristo Couloir and our eventual goal, near the eastern most false summit of Northstar Mountain. This area was situated below a developing cornice and was freshly loaded with 8" of heavy, wind-deposited snow on top of 4" of snow from the night before. All of this was resting on a firm crust from last week's dump. We cut and tested a column with a compression test. The interface 8" down collapsed at 7 taps but did not release and a strong slab (on top of last week's snow) released about 12" down after 16 taps revealing a smooth, firm bed surface.
Avalanche
A 60-80' wide slab (I would guess about 8-12" deep based on pit and the amount of debris at the bottom of the slide path) broke off at 14'000, just below the first convexity that tops the Cristo Couloir. This first slide ran to the second, steeper rollover, triggering another slab that propagated out far to the lookers left. The lower crown zigzagged following the left side of the couloir, but appeared to be about 300' wide in total Please note I did not see the avalanche occur, only saw the path from a distance. The slide path ran nearly the entire length of the couloir, about 2000 vertical feet. There did not appear to be any tracks heading into the couloir and no one was visible from my vantage point.